Lassa fever A96.2

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 18.12.2020

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Synonym(s)

LAS-HF; Lassa Fever; Lassa-hemorrhagic fever

History
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Frame JD, Baldwin JM Jr, Gocke DJ, Troup JM (1970)

Definition
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A severe febrile, haemorrhagic, often lethal infection caused by the Lassa virus, which is caused by the infectious urine of the many teat rat and nosocomially after contact with infectious secretions.

Pathogen
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Genus Arenavirus, family Arenaviridae, belonging to the family of viral haemorrhagic fever

Occurrence/Epidemiology
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First description in Nigeria in 1969: one American missionary nurse fell ill and died, another fell ill and was treated in the USA; there the virus was sioled for the first time; named after the city where the nurse worked.

Endemic in West Africa: Nigeria, Liberia, Sierra Leone, Guinea, Mali, Senegal, Burkina Faso, Democratic Republic of Congo, Ghana, Ivory Coast.

High regional infestation (up to 50% of the population).

In West Africa about 100,000-300,000 cases of Lassa fever annually, about 70% are subclinical.

Case Fatality Rate: 2-30% (especially pregnant women).

Lassa-related virus is the Mopeia virus in South Africa, Mozambique, Zimbabwe.

In Germany, only very few cases have become known since the first description.

Etiopathogenesis
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Reservoir animal is the multi-tip rat Mastomys natalensis. Infectious urine of the healthy appearing rat contaminates the human environment. Nosocomial infection through infectious secretions.
  • Herd-shaped necroses in the liver, adrenal glands, spleen.
  • Generalized, virally suspected endothelial and platelet dysfunction.

Clinical features
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incubation period: 8-10 days. Insidious, uncharacteristic picture.

1st-2nd week of illness: Highly painful pharyngitis, cough, retrosternal pain. Viral exanthema may occur. There is massive bleeding tendency in/from the conjuctives (injection) and other mucous membranes. Hemorrhages and purpura are often severe. There is also oedema of the face and neck, lymphadenopathy, pleural or pericardial effusions, possibly bloody diarrhoea, convulsions as a sign of encephalopathy, hypovolaemic shock, anuria, coma.

Laboratory
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lymphocytopenia, possibly neutrophilia

Increase in residual nitrogen

hematocrit increase

Proteinuria

thrombocytopenia

Increase in transaminase levels.

Diagnosis
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  • Isolation of the pathogen from blood, pharyngeal washings and urine
  • Virus antigen detection (ELISA)
  • Antibody detection (immunofluorescence and ELISA).

Differential diagnosis
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Influenza (at the beginning of the disease); other haemorrhagic fevers; malaria; rickettsialpox.

Complication(s)
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During pregnancy most severe clinical picture with high lethality.

If the disease survives, slow recovery, temporary hair loss and hearing loss.

Therapy
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Ribavirin (Virazoles): initially once/day 30 mg/kg bw for 6 days, then once/day 16 mg/kg bw for 4 days, then once/day 8 mg/kg bw i.v. for 2 days.

Notice! In Germany, Virazole is only approved for inhalation application, but internationally also for i.v. application. There is an exceptional indication for i.v. application!

Early application of reconvalescent plasma (abandoned due to possible transmission of hepatitis B, C and HI virus).

Prophylaxis
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Rodent control. Observance of general hygiene in health care.

Sick people must be strictly isolated.

Pre-exposure to ribavirin for laboratory staff, doctors, etc.

Post-exposure ribavirin intake is critically discussed and is generally not recommended.

Note(s)
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Remember! Suspected illness, illness and death must be reported by the doctor to the public health department by name according to §6 IfSG. According to § 7 IfSG there is an obligation to report in case of direct or indirect evidence of the virus.

Literature
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  1. Akpede GO et al (2018)Lassa fever outbreaks in Nigeria. Expert Rev Anti Infect Ther 16:663-666.
  2. Frame JD, Baldwin JM, Gocke DJ, Troup JM (1970) "Lassa fever, a new virus disease of man from West Africa. I. Clinical description and pathological findings". On J Trop Med Hyg 19: 670-676
  3. The Lancet Infectious Diseases (2018). Lassa fever and global health security. Lancet Infect Dis 18:357.

Disclaimer

Please ask your physician for a reliable diagnosis. This website is only meant as a reference.

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Last updated on: 18.12.2020