seminar presentation on lassa fever

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• Lassa Fever Training

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• About Viral Hemorrhagic Fevers

Lassa Fever Training for Healthcare Providers

While viral hemorrhagic fevers, like Lassa fever, are very serious, they are not common in the U.S. However, it is important for doctors and advanced practice nurses to be familiar with the risk factors, endemic areas, incubation period and clinical presentation of viruses, like Lassa virus, so they can appropriately diagnose their patients.

What you will learn

This video provides an overview of Lassa fever for clinicians. Background information on Lassa fever in this video provides context for health care providers as they move through additional modules that focus on the epidemiology and clinical presentation of Lassa fever, as well as diagnostics and treatment.

By the end of this training, you will be able to:

• Describe the epidemiology of Lassa fever.
• Describe the clinical presentation of Lassa fever.
• Identify 2 methods to diagnose Lassa fever in clinical settings.
• Describe the considerations for clinical management of Lassa fever.
• Describe my scope of practice as a team member in identifying or diagnosing Lassa fever.

Training information

CE origination date: June 3, 2024

CE expiration date: June 3, 2026

Prerequisites: General knowledge of infectious diseases.

Format: This activity is Web-on-Demand.

Instructions for obtaining continuing education (CE)

To receive continuing education (CE) for WD4851- Lassa Fever: What healthcare professionals need to know to recognize, treat, and prevent Lassa fever , please visit CDC TRAIN and search for the course in the Course Catalog using WD4851 .

Follow the steps below by June 3, 2026 .

• Register for and complete the course.
• Pass the post-assessment at [ 75] %.
• Complete the evaluation.
• Visit Your Learning to access your certificates and transcript.

No fees are charged for CDC's CE activities.

Accreditation statement

In support of improving patient care, The Centers for Disease Control and Prevention is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.

CME: The Centers for Disease Control and Prevention designates this enduring activity for a maximum of 0.75 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

CNE: The Centers for Disease Control and Prevention designates this activity for 0.75 nursing contact hours.

Disclosure: In compliance with continuing education requirements, all planners and presenters must disclose all financial relationships, in any amount, with ineligible companies during the previous 24 months as well as any use of unlabeled product(s) or products under investigational use.

CDC, our planners, and content experts wish to disclose they have no financial relationship(s) with ineligible companies whose primary business is producing, marketing, selling, reselling, or distributing healthcare products used by or on patients.

Content will not include any discussion of the unlabeled use of a product or a product under investigational use with the exception of Dr. Aaron Kofman's discussion of Lassa fever treatment. He will be discussing the summative clinical evidence to date for the use of ribavirin, favipiravir and monoclonal antibodies for the treatment of Lassa fever. He does not provide original data on these topics.

CDC did not accept financial or in-kind support from ineligible companies for this continuing education activity.

Lassa Fever

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LASSA FEVER- WHAT YOU NEED TO KNOW. INTRODUCTION Lassa fever is a viral hemorrhagic fever Caused by Lassa Virus First identified in Lassa town, Borno.

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Lassa Fever

Lassa fever by abhinay sharma bhugoo viral hemorrhagic fever caused by the arenavirus lassa transmitted from rodents to humans discovered in nigeria, 1969 endemic in ... – powerpoint ppt presentation.

• By abhinay sharma bhugoo
• Viral hemorrhagic fever caused by the Arenavirus Lassa
• Transmitted from rodents to humans
• Discovered in Nigeria, 1969
• Endemic in portions of West Africa
• Seasonal clustering Late rainy and early dry season
• Affects all age groups and both sexes
• Name derived from arenosus (Latin sandy) describing appearance of virions on examination by electron microscopy
• Enveloped virus, round or pleomorphic, 50-300 nm in diameter
• Single-stranded genome divided into 2 RNA segments small (3.4 kb) and large (7.1 kb)
• 2 genes on each segment, arranged in unique ambisense orientation, encoding 5 proteins
• Inactivated by
• heating to 56oF
• pHlt5.5 or gt8.5
• UV/gamma irradiation
• Arenaviruses associated with human disease
• Virus Origin of Name Year Distribution
• Lassa Town, Nigeria 1969 West Africa
• Junin Town, Argentina 1957 South America
• Machupo River, Bolivia 1962 South America
• Guanarito Area, Venezuela 1989 South America
• Sabia Town, Brazil 1990 South America
• LCMV Clinical disease 1933 Worldwide
• Endemic in areas of West Africa, including Nigeria, Liberia, Sierra Leone, and Guinea
• Estimated 300,000-500,000 infections/year, with 5000 deaths
• Rodent-to-human transmission (the multimammate rat, Mastomys species-complex)
• Secondary human-to-human transmission with the potential for nosocomial outbreaks with high case-fatality
• Mastomys species complex
• Taxonomy still unclear
• M. huberti more common in peridomestic habitat
• M. erytholeucus more common in brush habitat
• Rodent-to-human
• Inhalation of aerosolized virus
• Ingestion of food or materials contaminated by infected rodent excreta
• Catching and preparing Mastomys as a food source
• Human-to-human
• Direct contact with blood, tissues, secretions or excretions of infected humans
• Needle stick or cut
• Endothelial cell damage/capillary leak
• Platelet dysfunction
• Suppressed cardiac function
• Cytokines and other soluble mediators of shock and inflammation
• Incubation period of 5-21 days
• Gradual onset of fever, headache, malaise and other non-specific signs and symptoms
• Pharyngitis, myalgias, retro-sternal pain, cough and gastrointestinal symptoms typically seen
• A minority present with classic symptoms of bleeding, neck/facial swelling and shock
• Case fatality of hospitalized cases 15-20
• Particularly severe in pregnant women and their offspring
• Deafness a common sequela
• Increased maternal mortality in third trimester (gt30)
• Increased fetal and neonatal mortality (gt85)
• Increased level of viremia in pregnant women
• Placental infection
• Evacuation of uterus improves mothers chance of survival
• Typically appears during early convalescence
• Not related to severity of acute illness
• Occurs in one-third of cases
• May be bilateral or unilateral
• May persist for life in up to one-third of those affected
• Significant cause of pediatric hospitalizations in some areas of West Africa
• Signs and symptoms most often similar to adults
• Swollen Baby Syndrome
• - Edema/Anasarca
• - Abdominal distension
• - Poor prognosis
• Typhoid fever
• Streptococcal pharyngitis
• Leptospirosis
• Bacterial sepsis
• Bacterial meningitis
• Arboviral infection
• Anicteric hepatitis
• Enterovirus infection
• Bacterial or viral conjuctivitis
• Clinical diagnosis often difficult
• ELISA (Enzyme-linked immunosorbent assays) for antigen, IgM, and IgG
• As research tools
• Virus isolation
• Immunohistochemistry (for post-mortem diagnosis)
• RT-PCR (Reverse transcription-polymerase chain reaction)
• Supportive measures
• Most effective when started within the first 6 days of illness
• Major toxicity mild hemolysis and suppression of erythropoesis. Both reversible
• Presently contraindicated in pregnancy, although may be warranted if mothers life at risk
• Does not appear to reduce incidence or severity of deafness
• High viremia
• Serum AST level gt150 IU/L
• Encephalitis
• Third trimester of pregnancy
• Village-based programs for rodent control and avoidance
• Hospital training programs to avoid nosocomial spread barrier nursing manual
• Diagnostic technology transfer
• Specific antiviral chemotherapy (ribavirin)

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Lassa Fever

Jan 02, 2020

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Lassa Fever. Special Pathogens Branch NCID/DVRD CDC. General Facts. Viral hemorrhagic fever caused by the Arenavirus Lassa Transmitted from rodents to humans Discovered in Nigeria, 1969 Endemic in portions of West Africa Seasonal clustering: Late rainy and early dry season

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Lassa Fever Special Pathogens Branch NCID/DVRD CDC

General Facts • Viral hemorrhagic fever caused by the Arenavirus Lassa • Transmitted from rodents to humans • Discovered in Nigeria, 1969 • Endemic in portions of West Africa • Seasonal clustering: Late rainy and early dry season • Affects all age groups and both sexes

Arenaviridae • Name derived from “arenosus” (Latin “sandy”) describing appearance of virions on examination by electron microscopy • Enveloped virus, round or pleomorphic, 50-300 nm in diameter • Single-stranded genome divided into 2 RNA segments: small (~3.4 kb) and large (~7.1 kb) • 2 genes on each segment, arranged in unique “ambisense” orientation, encoding 5 proteins • Inactivated by: • heating to 56oC • pH<5.5 or >8.5 • UV/gamma irradiation • detergents

Arenaviridae • Arenaviruses associated with human disease VirusOrigin of NameYearDistribution LassaTown, Nigeria 1969 West Africa JuninTown, Argentina1957 South America MachupoRiver, Bolivia 1962South America GuanaritoArea, Venezuela 1989South America SabiaTown, Brazil 1990 South America LCMV Clinical disease 1933 Worldwide

Lassa Virus Image source: C.S. Goldsmith and M. Bowen (CDC).

Epidemiology • Endemic in areas of West Africa, including Nigeria, Liberia, Sierra Leone, and Guinea • Estimated 300,000-500,000 infections/year, with 5000 deaths • Rodent-to-human transmission (the “multimammate rat”, Mastomys species-complex) • Secondary human-to-human transmission with the potential for nosocomial outbreaks with high case-fatality

Known Distribution of Mastomys MASTOMYS DISTRIBUTION LASSA 1969

Rodent Reservoir • Mastomys species complex • Taxonomy still unclear • M. huberti: more common in peridomestic habitat • M. erytholeucus: more common in brush habitat • Others

Transmission • Rodent-to-human: • Inhalation of aerosolized virus • Ingestion of food or materials contaminated by infected rodent excreta • Catching and preparing Mastomys as a food source

Transmission • Human-to-human: • Direct contact with blood, tissues, secretions or excretions of infected humans • Needle stick or cut • Inhalation of aerosolized virus

Pathogenesis • Endothelial cell damage/capillary leak • Platelet dysfunction • Suppressed cardiac function • Cytokines and other soluble mediators of shock and inflammation

Clinical Aspects • Incubation period of 5-21 days • Gradual onset of fever, headache, malaise and other non-specific signs and symptoms • Pharyngitis, myalgias, retro-sternal pain, cough and gastrointestinal symptoms typically seen • A minority present with classic symptoms of bleeding, neck/facial swelling and shock • Case fatality of hospitalized cases: 15-20% • Particularly severe in pregnant women and their offspring • Deafness a common sequela

Clinical Signs and Symptoms Fever Headache Arthralgias/Myalgias Retro-sternal Pain Weakness Dizziness Sore throat/Pharyngitis Cough Vomiting Abdominal Pain/Tenderness Diarrhea Conjunctivitis/Sub-conjunctival Hemorrhage Chills Deafness Lymphadenopgathy Bleeding Confusion Swollen Neck or Face 0 10 20 30 40 50 60 70 80 90 100 Percent

Lassa Fever in Pregnancy • Increased maternal mortality in third trimester (>30%) • Increased fetal and neonatal mortality (>85%) • Increased level of viremia in pregnant women • Placental infection • Evacuation of uterus improves mother’s chance of survival

Sensorineural Hearing Deficit in Lassa Fever • Typically appears during early convalescence • Not related to severity of acute illness • Occurs in one-third of cases • May be bilateral or unilateral • May persist for life in up to one-third of those affected

Lassa Fever in Children and Infants • Significant cause of pediatric hospitalizations in some areas of West Africa • Signs and symptoms most often similar to adults • “Swollen Baby Syndrome” - Edema/Anasarca - Abdominal distension - Bleeding - Poor prognosis

Malaria Typhoid fever Streptococcal pharyngitis Leptospirosis Bacterial sepsis Bacterial meningitis Arboviral infection Anicteric hepatitis Enterovirus infection Bacterial or viral conjuctivitis Differential Diagnosis of Lassa Fever

Diagnostics • Clinical diagnosis often difficult • ELISA (Enzyme-linked immunosorbent assays) for antigen, IgM, and IgG • As research tools: • Virus isolation • Immunohistochemistry (for post-mortem diagnosis) • RT-PCR (Reverse transcription-polymerase chain reaction)

Treatment • Supportive measures • Ribavirin • Most effective when started within the first 6 days of illness • Major toxicity: mild hemolysis and suppression of erythropoesis. Both reversible • Presently contraindicated in pregnancy, although may be warranted if mother’s life at risk • Does not appear to reduce incidence or severity of deafness

Associated with Poor Prognosis in Lassa Fever • High viremia • Serum AST level >150 IU/L • Bleeding • Encephalitis • Edema • Third trimester of pregnancy

Prevention and Control • Village-based programs for rodent control and avoidance • Hospital training programs to avoid nosocomial spread: barrier nursing manual • Diagnostic technology transfer • Specific antiviral chemotherapy (ribavirin)

Rodent Control • Proper storage of food in rodent-proof containers • Cleaning around homes • Trapping and killing rodents with proper and safe disposal of carcasses • Avoid rodents as a food source

Ongoing Lassa Fever Research in Guinea, West Africa • Natural history of disease • Where it came from • How clinical course progresses • Whom it affects • Diagnosis: Clinical/Laboratory • Immunopathogenesis • Treatment • Rodent population dynamics • Prevention and control Collaboration between CDC/SPB and the Guinean Institute for Research and Applied Biology

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Course is available

Lassa fever: Introduction

Lassa fever, a viral haemorrhagic fever with symptoms similar to those of Ebola virus disease, is endemic in much of West Africa and usually sparks a seasonal outbreak from December to March. Humans usually become infected with Lassa virus from exposure to urine and faeces of infected Mastomys rats. Lassa virus may also be spread between humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person infected with Lassa fever. This course provides a general introduction to Lassa fever and is intended for personnel responding to outbreaks in complex emergencies or in settings where the basic environmental infrastructures have been damaged or destroyed.

**Please note : This course was developed in 2018. For the latest updates, please refer to the relevant health topics on the WHO website .

Course information

La version française de ce cours est disponible sur : https://openwho.org/courses/fievre-de-lassa-introduction

Overview : Lassa fever, a viral haemorrhagic fever with symptoms similar to those of Ebola virus disease, is endemic in much of West Africa and usually sparks a seasonal outbreak from December to March. Humans usually become infected with Lassa virus from exposure to urine and faeces of infected Mastomys rats. Lassa virus may also be spread between humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person infected with Lassa fever. Lassa fever occurs in all age groups and both sexes. Persons at greatest risk are those living in rural areas where Mastomys are usually found, especially in communities with poor sanitation or crowded living conditions. This course provides a general introduction to Lassa fever through a downloadable presentation that can be reviewed at your own pace and quizzes to test your knowledge. It is intended for personnel responding to outbreaks of Lassa fever in complex emergencies or in settings where the basic environmental infrastructures have been damaged or destroyed.

Learning objectives: By the end of this course, participants should be able to:

• describe signs, symptoms, and transmission routes of Lassa fever;
• list prevention and control techniques; and
• describe Lassa fever's public health challenges.

Course duration : Approximately 1 hour.

Certificates : A Confirmation of Participation is available to participants who complete at least 80% of the course materials.

Course contents

Lassa fever:, enroll me for this course, certificate requirements.

• Gain a Confirmation of Participation by completing at least 80% of the course material.

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Lassa fever: epidemiology, clinical features, and social consequences

J kay richmond, deborah j baglole.

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Correspondence to: J K Richmond [email protected]

Short abstract

Lassa fever is endemic in west Africa, where it probably kills several thousand people each year. With access to the region improving, the opportunity, and the need, to improve our understanding of this disease are increasing

Lassa fever is a viral haemorrhagic fever transmitted by rats. It has been known since the 1950s, but the virus was not identified until 1969, when two missionary nurses died from it in the town of Lassa in Nigeria. Found predominantly in west Africa, 1 it has the potential to cause tens of thousands of deaths. Even after recovery, the virus remains in body fluids, including semen. 1 The years of civil unrest in Sierra Leone (1991-2002) halted the investigation (through international collaboration) of Lassa fever at a specialist unit in Kenema. Increasing international travel and the possibility of use of the Lassa virus as a biological weapon escalate the potential for harm beyond the local level. Access to the country is improving, so renewed efforts to understand it are feasible.

Method of review

The information presented comes from a strategic document produced in 2002 for Merlin (Medical Emergency Relief International, a London based nongovernmental aid organisation which manages the Lassa unit in Kenema ( www.merlin.org.uk )). This document, `Licking' Lassa fever , 2 was created through collaboration with experts in infectious disease, community development, clinical management of viral haemorrhagic diseases, and qualitative research. The sources of information were a literature review using Ovid and PubMed (search term “Lassa fever”), case analysis and surveys undertaken in the field, and relevant websites (such as those of the World Health Organization, Centers for Disease Control and Prevention).

Epidemiology

Lassa fever is caused by a single stranded RNA virus and is a disseminated systemic primary viral infection. 3 , 4 The main feature of fatal illness is impaired or delayed cellular immunity leading to fulminant viraemia. 5 The prevalence of antibodies to the virus in the population is 8-52% in Sierra Leone, 6 4-55% in Guinea, 7 and 21% in Nigeria. 8 Seropositivity has also been found in the Central African Republic, Democratic Republic of the Congo, Mali, and Senegal (see figure ). 1 Staff from the UK Department for International Development, the International Committee of the Red Cross, and the United Nations Mission in Sierra Leone have succumbed. Sporadic cases have occurred in travellers returning to Britain, the Netherlands, and Germany.

Distribution of Lassa fever in west Africa. Outbreaks have occurred in the Central African Republic, Guinea, Liberia, Nigeria, and Sierra Leone; serological evidence of human infection has been found in the Democratic Republic of the Congo, Mali, and Senegal

Summary points

Lassa fever, a viral haemorrhagic fever transmitted by rats, is endemic in west Africa and may kill tens of thousands of people each year

Peak incidence was thought to be in the dry season (January to March), but data collected in Sierra Leone shows peaks in the overlap with the wet season (May to November)

Many infections are subclinical; a high index of suspicion, given the difficulties of clinical diagnosis, is needed when travellers from west Africa present with a fever of unknown origin, with symptoms appearing up to 21 days after leaving the endemic area

The virus is excreted in semen for three months after infection; we do not know how frequently it may be transmitted through sexual intercourse

Attempts are being made to produce a vaccine using the yellow fever virus as a vehicle

The possibility that Lassa virus could be used as a biological weapon has raised the profile of the need for greater understanding of Lassa fever and for more effective control and treatment programmes

The natural hosts for the virus are multimammate rats ( Mastomys natalensis ), which breed frequently and are distributed widely throughout west, central, and east Africa. 3 They are probably the most common rodent in tropical Africa and are found predominantly in rural areas, and in dwellings more often than in surrounding countryside. 6 Members of the genus are infected persistently and shed the virus in their excreta. Humans are infected by contact with the rats or by eating them (they are considered a delicacy and are eaten by up to 90% of people in some areas). Rats found in houses of infected people are seropositive for the virus 10 times more often than those in control houses. 9 Virus antibodies occur after a febrile illness in twice as many people who eat rats as in those who do not, and deafness (an effect of Lassa fever) occurs four times more frequently. 10

Morbidity and mortality

Presentation of cases used to be highest during the dry season (January to March) and lowest during the wet season (May to November). However, recent data from Kenema (1999-2002) show that admissions were highest during the change from the dry to the wet season (see fig A on bmj.com ). This change might be related partly to population movements during the civil unrest in Sierra Leone (see fig B on bmj.com ) 11 and overcrowding among refugees. Travel becomes increasingly difficult as the wet season progresses and may help to account for the decrease in numbers of cases later in the season. All the cases reported were diagnosed clinically. Until 1998 laboratory confirmation of diagnosis was available retrospectively and 60-70% of cases were confirmed, 12 but in 2000 over half of a series of 22 cases were wrongly diagnosed. Thus, these recent apparent changes in infection patterns must be interpreted with caution.

People of all ages are susceptible. The disease is mild or has no observable symptoms in about 80% of people infected, but 20% have a severe multisystem disease. The incubation period is 6-21 days. The virus is excreted in urine for three to nine weeks from infection and in semen for three months. 1 The extent of sexual transmission is unknown.

Sensorineural hearing deficit is a feature of the disease: it was found in 29% of confirmed cases compared with none of febrile controls in hospital inpatients. 13 In the general population, 81% of those who experienced sudden deafness had antibodies to Lassa virus versus 19% of matched controls. There is no apparent relation between the severity of viral illness, initial hearing loss, or subsequent recovery. 14

Lassa fever was responsible for 10-16% of all adult medical admissions in 1987 in two hospitals studied in Sierra Leone and for about 30% of adult deaths. 15 The case fatality rate in Kenema varied from 12% to 23% for the period 1997-2002. A recent case series showed low admission rates and high case fatality rates for people aged less than 18 years (who make up 51% of the total population (United Nations Development Programme)) compared with older people (see table A on bmj.com ). During pregnancy, high rates of maternal death (29%) and fetal and neonatal loss (87%) have been recorded (uterine evacuation improves outcome significantly), with 25% of all maternal deaths in Sierra Leone being due to Lassa fever. 16 An estimate of the case fatality rate in the general population is 1-2%, much lower than in hospitalised cases, possibly as a consequence of differences in severity.

Using the figures for rural populations (available from the United Nations Development Programme) and the epidemiology of the disease, we estimate that the “at risk” seronegative population (in Sierra Leone, Guinea, and Nigeria) may be as high as 59 million, with an annual incidence of illness of three million, fatalities up to 67 000, and up to three million reinfections ( table 1 ). Until a complete picture of Lassa fever is known, these are rough estimates. Comparable data are unavailable for the other countries where seropositivity has been recorded.

Estimates of seropositivity and mortality from Lassa fever in Guinea, Nigeria, and Sierra Leone (values are numbers of people unless stated otherwise)

NA=Not available.

Data from United Nations Development Programme.

Peace keepers within Sierra Leone have been affected by Lassa fever. 17 Case records in Kenema for July-September 2002 show 11 admissions from the Sierra Leone army and 10 from the United Nations mission in Sierra Leone, with one death in each group.

Clinical course

Lassa fever presents with symptoms and signs indistinguishable from those of febrile illnesses such as malaria and other viral haemorrhagic fevers such as Ebola. It is difficult to diagnose clinically but should be suspected in patients with fever (≥38°C) not responding adequately to antimalarial and antibiotic drugs ( table 2 ). The most useful clinical predictors of Lassa fever are fever, pharyngitis, retrosternal pain, and proteinuria for diagnosis; and fever, sore throat, and vomiting for outcome. 15

Clinical stages of Lassa fever (adapted from McCarthy 2002 18 )

Complications include mucosal bleeding (17%), sensorineural hearing deficit (4%), pleural effusion (3%), and pericardial effusion (2%). 15 The outcome is related to the degree of viraemia, not the antibody response, and is worse with high levels of aspartate aminotransferase. 4

On the basis of a case series of 140 men and 128 women admitted in Kenema during 2001, the duration of illness can vary considerably (table B on bmj.com ). The commonest interval between onset of symptoms and discharge was 17 days (half of the patients were in hospital for 10 days) and between onset and death was five days (half died within two days of admission). Delays between onset and admission resulted in most patients not receiving ribavirin within the critical first six days. These data add to the uncertainty surrounding diagnosis and lethality.

Laboratory investigation

At hospital admission, most patients have antibodies to the virus (53% with IgG and 67% with IgM). 4 Together, enzyme linked immunosorbent assays (ELISAs) for Lassa virus antigen and for virus IgM are 88% sensitive and 90% specific for acute infection. 19 Other effects of illness include lymphocytopenia and a moderate thrombocytopenia, which are maximal 10-11 days after the onset of symptoms. 20 The thrombocytopenia is associated with a serum inhibitor and with the occurrence of haemorrhage, depression of platelet aggregation, and the severity of Lassa fever. 21 With reverse transcription polymerase chain reaction, Lassa fever can be diagnosed in all patients by the third day of illness, but immunoflourescence identifies only 52% of the patients. 22

Clinical management

All suspected cases should be admitted to isolation facilities. Hospital transmission occurs through inadequate infection control measures. 23 Strict isolation of cases and procedures for handling body fluids and excreta must be maintained. 2

Ribavirin and general support are needed. 24 Ribavirin is almost twice as effective when given intravenously as when taken orally, and if given within six days of the start of illness it may reduce deaths by 90%. Dehydration, oedema, hypotension, and poor renal function are common; fluid replacement or the use of blood transfusion requires careful monitoring.

Surveillance and disease control

Surveillance should identify all close contacts of the patients for three weeks after the start of illness, and a search initiated for unreported or undiagnosed cases. 1 Two areas of concern are, firstly, the treatment of undiagnosed cases in hospitals where overcrowding and poor hygiene can spread the disease to other patients, staff, or visitors; and, secondly, traditional burial ceremonies for infected corpses, with the possible risk of spread to many people.

Production of a combined, single dose vaccine against yellow fever and Lassa fever has been proposed. 25 The cost and logistical problems of delivering it would be huge, particularly since fewer than 20% of districts in the countries studied achieve 80% uptake of childhood vaccination. 2 Use for visitors from the United Nations, non-governmental organisations, and business communities might make it financially viable, even though it is the most expensive of the possible control strategies.

Community perspectives

Civil unrest severs supply and trading links, and people want for basic commodities. Migration disrupts agricultural cycles, reduces farming activities, and encourages looting, killing of livestock, and destruction of property. People are forced into overcrowded camps and public buildings, and spread of communicable diseases is facilitated.

Adverse influences of Lassa fever on socioeconomic wellbeing are mediated through the inability of patients to care for themselves and their dependants, the high death rate in hospital, nosocomial transmission to staff and the subsequent loss of service, and the occurrence of hearing loss through clinical and subclinical infection.

Knowledge, attitude, and practice survey

During 2001, a knowledge, attitude, and practice survey was undertaken in Kenema among 813 men and 867 women in four camps for internally displaced people and eight primary health units. The survey revealed a reasonable knowledge of Lassa fever, its mode of transmission, control measures, and the seriousness of the disease. However, there were some worrying gaps in application of this knowledge, such as inappropriate actions after killing rats (see fig C on bmj.com ). This was demonstrated by the occurrence of an outbreak of 823 cases, including 153 deaths (case fatality rate 19%), from January 1996 to April 1997, after an extensive outreach programme. 1 The need for greater understanding of the perceptions and beliefs of the local population became apparent.

Qualitative study

A small pilot study (of 23 people) was undertaken through focus groups and interviews in 2002. The major concerns related to

Effective rodent control (“We have a rat which happens to be the sweetest meat, and you tell that person not to eat that meat because it creates Lassa fever”)

People understood that Lassa fever can be contracted through contact with an affected person—this leads to patients and their families being isolated and stigmatised (“When my wife was admitted to Lassa ward, well, it was not only an economic depression, it also created social embarrassment, because my children no longer go to other houses, to their relatives”)

Early diagnosis is impeded by the absence of a diagnostic test for use in the community and difficulties reaching health facilities (“No, no, what are you trying to tell me? I don't want you to be guessing in Lassa.... As far as Lassa is concerned, you have to be very much more serious, you don't have to be hypothetical, you have to correct in your diagnosis when you are treating Lassa fever... we need a lab.” “In the rainy seasons, the river runs, there is no means of transportation. Others, the location of the health facility is so far away, there is no ambulance service to transport the sick”)

Many people are unlikely to seek medical care if they suspect they have Lassa fever: treatment is expensive and can usually be afforded only by sacrificing necessities such as food and school fees (“There will be lots of gossiping, because there is no money at home and no food at home, you have to go to friends to get you some food, so you can help the children, or to take to the hospital”)

Belief in traditional remedies and mistrust of treatment offered at the hospital were described (“There are certain people in the community we live in, they believe in herbs, in going to the bush to get some tea herbs... they think herbs can mend them” “People don't go to medical facilities... especially when they say they have Lassa fever, they will be given injections to kill them”)

Miscarriage is blamed on the woman, is often attributed to witchcraft, and commonly leads to divorce (“People class you as a witch because you have aborted”)

Deafness was described as a social embarrassment and as having a catastrophic effect on family relationships (“She is now like someone who is crazy, stupid, because she has lost her hearing sense”).

Many of these factors lead to social exclusion.

Research needs

The epidemiology of both rat and human populations requires urgent investigation if we are to understand this disease fully. It could be done through developing

International collaboration over research

A map of the complete epidemiological and clinical story

Involvement of the communities affected

Effective and affordable diagnostic kits and treatment

Efficient and effective specialist treatment centres

An effective and affordable vaccine to control the infection in its natural habitat, protect international visitors, and deter the use of the virus as an agent of biological warfare.

The terrorist attack in New York on 11 September 2001 and the subsequent anthrax attacks served to alert governments to the potential of biological agents as weapons. A special report in the Lancet signposts increased funding for the National Institute for Allergy and Infectious Disease and its blueprint for research, including Lassa fever. 18 Thus, the need for a greater understanding of Lassa fever and for more effective control and treatment programmes has assumed a higher profile. The time is ripe for a concerted international effort to achieve these ends.

Additional educational resources

Merlin. Lassa fever publications— www.merlin.org.uk/template7.asp?PageID=178

WHO Information. Fact sheets: Lassa fever— www.who.int/inf-fs/en/fact179.html

WHO Communicable Disease Surveillance and Response (CSR). Lassa fever— www.who.int/csr/disease/lassafever/en/

WHO Communicable Disease Surveillance and Response (CSR). Disease outbreaks: Lassa fever— www.who.int/disease-outbreak-news/disease/A96.2.htm

CDC. Infectious disease information: viral hemorrhagic fever— www.cdc.gov/ncidod/diseases/virlfvr/virlfvr.htm

Health Protection Agency. Viral haemorrhagic fever (VHF)— www.hpa.org.uk/infections/topics_az/VHF/menu.htm

National Institute of Allergy and Infectious Diseases. NIAID biodefense research agenda for CDC category A agents . Bethesda, MD: US Department of Health and Human Services, National Institutes of Health, 2002 ( www.niaid.nih.gov/biodefense/research/biotresearchagenda.pdf ).

Supplementary Material

This article is based on the Merlin document `Licking' Lassa fever . We are grateful for comments on drafts from Dr Edward Coyle, director of Wales Centre for Health, Cardiff, and Professor T Cullinan, TB health adviser for Merlin, London.

Funding: `Licking' Lassa fever was produced under a grant from the Rockefeller Foundation.

Competing interests: JKR was employed by Merlin in 2002 as country medical coordinator in Sierra Leone and as main author and collator of the paper ` Licking' Lassa fever . DJB is employed by Merlin as a health adviser with responsibility for Sierra Leone.

• 1. World Health Organization. WHO Lassa fever fact sheet No 179. Geneva:WHO, 2000.
• 2. Merlin. `Licking' Lassa fever: a strategic review . London: Merlin, 2002. ( www.merlin.org.uk/uploads/files/pr/Lassa%20Fever%20Strategy%202.pdf )
• 3. Healing T, Gopal R. Report on an assessment visit to Sierra Leone, April 12th-30th 2001. London: Merlin, 2001.
• 4. Johnson KM, McCormick JB, Webb PA, Smith ES, Elliott LH, King IJ. Clinical virology of Lassa fever in hospitalized patients. J Infect Dis 1987;155: 456-64. [ DOI ] [ PubMed ] [ Google Scholar ]
• 5. Chen JP, Cosgriff TM. Hemorrhagic fever virus-induced changes in hemostasis and vascular biology. Blood Coagul Fibrinolysis 2000;11: 461-83. [ DOI ] [ PubMed ] [ Google Scholar ]
• 6. McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES. A prospective study of the epidemiology and ecology of Lassa fever. J Infect Dis 1987;155: 437-44. [ DOI ] [ PubMed ] [ Google Scholar ]
• 7. Lukashevich LS, Clegg JC, Sidibe K. Lassa virus activity in Guinea: distribution of human antiviral antibody defined using enzyme-linked immunosorbent assay with recombinant antigen. J Med Virol 1993;40: 210-7. [ DOI ] [ PubMed ] [ Google Scholar ]
• 8. Tomori O, Fabiyi A, Sorungbe A, Smith A, McCormick JB. Viral hemorrhagic fever antibodies in Nigerian populations. Am J Trop Med Hyg 1988;38: 407-10. [ DOI ] [ PubMed ] [ Google Scholar ]
• 9. Keenlyside RA, McCormick JB, Webb PA, Smith E, Elliott L, Johnson KM. Case-control study of Mastomys natalensis and humans in Lassa virus-infected households in Sierra Leone. Am J Trop Med Hyg 1983;32: 829-37. [ DOI ] [ PubMed ] [ Google Scholar ]
• 10. Ter Meulen J, Lukashevich I, Sidibe K, Inapogui A, Marx M, Dorlemann A, et al. Hunting of peridomestic rodents and consumption of their meat as possible risk factors for rodent-to-human transmission of Lassa virus in the Republic of Guinea. Am J Trop Med Hyg 1996;55; 661-6. [ DOI ] [ PubMed ] [ Google Scholar ]
• 11. Wilson M. Infectious diseases: an ecological perspective BMJ 1995;311: 1681-4. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 12. Bausch D. Lassa fever in Sierra Leone. London:Merlin, 2000.
• 13. Cummins D, McCormick JB, Bennett D, Samba JA, Farrar B, Machin SJ, et al. Acute sensorineural deafness in Lassa fever. JAMA 1990;264: 2093-6. [ PubMed ] [ Google Scholar ]
• 14. Liao BS, Byl FM, Adour KK. Audiometric comparison of Lassa fever hearing loss and idiopathic sudden hearing loss: evidence for viral cause. Otolaryngol Head Neck Surg 1992;106: 226-9. [ DOI ] [ PubMed ] [ Google Scholar ]
• 15. McCormick JB, King IJ, Webb PA, Johnson KM, O'Sullivan R, Smith ES, et al. A case-control study of the clinical diagnosis and course of Lassa fever. J Infect Dis 1987;155: 445-55. [ DOI ] [ PubMed ] [ Google Scholar ]
• 16. Price ME, Fisher-Hoch SP, Craven RB, McCormick JB. A prospective study of maternal and fetal outcome in acute Lassa fever infection during pregnancy. BMJ 1988;297: 584-7. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 17. Ter Meulen J, Lenz O, Koivogui L, Magassouba N, Kaushik SK, Lewis R, et al. Short communication: Lassa fever in Sierra Leone: UN peacekeepers are at risk. Trop Med Int Health 2001;6: 83-4. [ DOI ] [ PubMed ] [ Google Scholar ]
• 18. McCarthy M. USA moves quickly to push biodefence research. Lancet 2002;360: 732. [ DOI ] [ PubMed ] [ Google Scholar ]
• 19. Bausch DG, Rollin PE, Demby AH, Coulibaly M, Kanu J, Conteh AS, et al. Diagnosis and clinical virology of Lassa fever as evaluated by enzyme-linked immunosorbent assay, indirect fluorescent-antibody test, and virus isolation. J Clin Microbiol 2000;38: 2670-7. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 20. Fisher-Hoch S, McCormick JB, Sasso D, Craven RB. Hematologic dysfunction in Lassa fever. J Med Virol 1988;26: 127-35. [ DOI ] [ PubMed ] [ Google Scholar ]
• 21. Cummins D, Fisher-Hoch SP, Walshe KJ, Mackie IJ, McCormick JB, Bennett D, et al. A plasma inhibitor of platelet aggregation in patients with Lassa fever. Br J Haematol 1989;72: 543-8. [ DOI ] [ PubMed ] [ Google Scholar ]
• 22. Demby AH, Chamberlain J, Brown DW, Clegg CS. Early diagnosis of Lassa fever by reverse transcription-PCR. J Clin Microbiol 1994:32; 2898-903. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 23. Fisher-Hoch SP, Tomori O, Nasidi A, Perez-Oronoz GI, Fakile Y, Hutwagner L, et al. Review of cases of nosocomial Lassa fever in Nigeria: the high price of poor medical practice. BMJ 1995;311: 857-9. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 24. McCormick JB, King IJ, Webb PA, Scribner CL, Craven RB, Johnson KM, et al. Lassa fever. Effective therapy with ribavirin. N Engl J Med 1986;314: 20-6. [ DOI ] [ PubMed ] [ Google Scholar ]
• 25. Fisher-Hoch SP, McCormick JB. Towards a human Lassa fever vaccine. Rev Med Virol 2001;11: 331-41. [ DOI ] [ PubMed ] [ Google Scholar ]

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