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INITIAL SYMPTOMS:
Flu-like illness with fever, myalgia, exudative pharyngitis, cervical adenopathy; conjunctivitis, vomiting, abdominal pain, chest pain, and cough; [CCDM]
FINDINGS:
About 80% of infections are asymptomatic or mild. Findings of severe infections may include shock, pleural effusions, hemorrhages, seizures, encephalopathy, albuminuria, elevated liver enzymes, and nerve deafness (eighth cranial nerve). [CCDM, p. 50-4] The typical case starts as a flu-like illness with pharyngitis, cough, chest pain, conjunctivitis, and abdominal pain. Some patients then develop the severe form of the disease with neck swelling and mild bleeding from the conjunctiva, nose, mouth, gastrointestinal, and genitourinary tracts. Maculopapular or petechial rashes may be visible in patients with lighter skin complexions. Some patients deteriorate with delirium, respiratory distress, shock, coma, and death. [Guerrant, p. 456-7] By the end of the first week, patients are very ill with high fever. Common symptoms are conjunctivitis, stomatitis, pharyngitis, cervical lymphadenopathy, abdominal pain, myalgias, arthralgias, hypotension, and relative bradycardia. There is no typical rash. Most patients do not have evidence of neurological disease. Leukopenia is common early in the illness, and leukocytosis is seen later. Platelet counts are not depressed, but platelet function is impaired. [ID, p. 2136] Common symptoms are fever, pharyngitis, chest pain, and proteinuria. Other findings are mucosal bleeding, encephalitis, stiff neck, pulmonary edema, and pleural effusions. [PPID, p. 2035-6] Lassa fever may present with fever, sore throat, jaundice, and hemorrhagic manifestations. [PPID, p. 3569] Transient blindness from iridocyclitis is a late complication. [Merck Manual., p. 1435]
EPIDEMIOLOGY:
Lassa fever is a common disease in West Africa with thousands to tens of thousands of cases a year. [ID, p. 2133] For hospitalized patients, case-fatality rate is as high as 15%. Transmission occurs through contact with infected rodents or infected patients (blood, urine, throat secretions, and sexual contact). Patients excrete the virus in urine for several weeks and in the semen for up to 3 months. [CCDM, p. 50-2] Infection spreads from infected rodents (small particle aerosols) and infected people (close contact). [Harrison ID, p. 1044-5]
RELATED INFECTIONS:
Lujo disease is similar to Lassa fever based on observations of 5 patients, 4 of whom died. The virus has been isolated from a patient in Zambia. [CCDM, p. 51-2]
For updated text and symptoms of infectious diseases, see iddx.com.