Lassa fever pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [3]

Synonyms and keywords: Lassa hemorrhagic fever; LHF

Overview

Lassa fever is a zoonotic disease caused by Lassa virus and spread by multimammate rat vector. It is spread through person-to-person contact and direct contact with rodent excretion. Lassa virus enters the cell by the receptor-mediated endocytosis and undergoes very rapid replication and manifest the disease. After an incubation period of 1-24 days, the disease can manifest as fever, muscle aches, sore throat, nausea, vomiting, chest and abdominal pain, weakness, cough, headache, exudative pharyngitis, anemia, low blood pressure, and diarrhea.

Pathophysiology

The current case definition for suspecting Lassa fever is as follows.[1].

Unexplained fever at least 38oC or 100.4oF for one week or more
And 1 of the following:
▸ No response to standard treatment for most likely cause of fever (malaria, typhoid fever) the choice of regimen.
▸ Readmitted within 3 weeks of inpatient care for an illness with fever.
And 1 of the following
Edema or bleeding.
Sore throat and retrosternal pain/vomiting.
▸ Spontaneous abortion following fever.
Hearing loss following fever.

Pathogenesis

Transmission

Lassa Fever wikipedia.png[1][3]

Rodent to Human

  • Infection in humans typically occurs via exposure to animal excrement through the respiratory or gastrointestinal tracts.
  • Inhalation of tiny particles of infective material (aerosol) is believed to be the most significant means of exposure.
  • It is possible to acquire the infection through broken skin or mucous membranes that are directly exposed to infective material. In fatal cases, Lassa fever is characterized by impaired or delayed cellular immunity leading to fulminant viremia[3].
  • Finally, because Mastomys rodents are sometimes consumed as a food source, infection may occur via direct contact when they are caught and prepared for food.

Human to Human

  • There are a number of ways in which the virus may be transmitted, or spread, to humans.
  • This type of transmission occurs when a person comes into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus.
  • The virus cannot be spread through casual contact (including skin-to-skin contact without exchange of body fluids).
  • Person-to-person transmission is common in both village and health care settings, where, along with the above-mentioned modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles (this is called nosocomial transmission). Frequency of transmission via sexual contact has not been established. * Transmission through breast milk has also been observed.

Molecular Pathology

Microscopic Pathology

The images below display key features of microscopic pathology of Lassa virus.

References

  1. "The Centers for Disease Control and Prevention" (PDF).
  2. Flatz L, Rieger T, Merkler D, Bergthaler A, Regen T, Schedensack M; et al. (2010). "T cell-dependence of Lassa fever pathogenesis". PLoS Pathog. 6 (3): e1000836. doi:10.1371/journal.ppat.1000836. PMC 2847900. PMID 20360949.
  3. 3.0 3.1 "wikipedia".
  4. Yun NE, Walker DH (2012). "Pathogenesis of Lassa fever". Viruses. 4 (10): 2031–48. doi:10.3390/v4102031. PMC 3497040. PMID 23202452.
  5. Johnson KM, McCormick JB, Webb PA, Smith ES, Elliott LH, King IJ (1987). "Clinical virology of Lassa fever in hospitalized patients". J Infect Dis. 155 (3): 456–64. PMID 3805773.
  6. 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". Am J Trop Med Hyg. 19 (4): 670–6. PMID 4246571.
  7. Walker DH, McCormick JB, Johnson KM, Webb PA, Komba-Kono G, Elliott LH; et al. (1982). "Pathologic and virologic study of fatal Lassa fever in man". Am J Pathol. 107 (3): 349–56. PMC 1916239. PMID 7081389.
  8. McCormick JB, Walker DH, King IJ, Webb PA, Elliott LH, Whitfield SG; et al. (1986). "Lassa virus hepatitis: a study of fatal Lassa fever in humans". Am J Trop Med Hyg. 35 (2): 401–7. PMID 3953952.
  9. 9.0 9.1 9.2 9.3 9.4 "Public Health Image Library (PHIL), Centers for Disease Control and Prevention".

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