Arenavirus - Clinical syndromes, LCM, Lassa Fever, South American hemorrhagic fever

Clinical syndromes of Arenavirus

Among numerous Arenavirus, at least nine are known to cause human disease.

• Lymphocytic choriomeningitis (LCM)

• Lassa fever

• South American hemorrhagic fever

LCM

Lymphocytic choriomeningitis is caused by the lymphocytic choriomeningitis virus. Infection in humans is rare, mild, and symptomatic except in immunocompromised individuals. During pregnancy, LCM virus infection is severe and is associated with developmental defects in the fetus.

The incubation period is around 1-2 weeks.

In mild cases of Arenavirus infection, LCM presents headache and fever neck stiffness, myalgia, and photophobia. long-term effects include headache, paralysis psychological changes, aseptic meningitis, encephalitis, undifferentiated febrile illness, etc.

Illness can be biphasic, symptoms may reoccur 2-4 days after recovery from the first phase.

Lassa Fever

Lassa Fever is endemic in west Africa. The majority of Arenavirus infection cases are asymptomatic while 20% demonstrate moderate to severe disease. The incubation period is around 1-3 weeks and is associated with hemorrhagic manifestation and multi-organ failure.

Gradual onset of fever, headache, muscle, and joint pain, and pharyngitis with non-productive cough is a common feature. In severe cases, vomiting, diarrhea, increased level of liver enzymes (ALT and AST), and raised hematocrit occur. Poor prognosis is indicated by abdominal and retrosternal pain, edema of the face and neck, enlarged lymph nodes, and hemorrhage of conjunctive or mucosal surfaces.

Recovery from Arenavirus takes 1-3 weeks and is associated with hearing loss while in fatal cases, fever is maintained and rapid deterioration occurs over the first 2 weeks and is associated with:

• hypovolaemia, hypotension, pleural effusion, ascites and anuria

• bleeding from gums, nose, intestine, or vagina, linked to platelet dysfunction

• acute neurological changes occur including unilateral or bilateral deafness, encephalopathy including seizures, dystonia, and neuropsychiatric changes

In pregnant women (especially in the 3^rd trimester) maternal mortality rate is 20% and the fetal mortality rate is near 100%. In children, the swollen baby syndrome is seen consisting of widespread edema, abdominal distension, and bleeding Blood platelet and lymphocyte count fall early in the illness.

South American hemorrhagic fever

South American hemorrhagic fever includes Argentinian Bolivian, Venezuelan, and Brazilian hemorrhagic fevers which are caused by Junin, Machupo, Guanarito, and Sabia virus respectively. Among these Argentinian hemorrhagic fever (AHF) is of major public health concern.

Around 80% of Arenavirus infections are mild to moderate and the incubation period is 1-2 weeks. The disease begins with the gradual onset of nondescript symptoms (eg: fever, muscle ache, dizziness, lymph node swelling, flushing of the face, neck, and upper chest).

After 6-10 days, 20-30% of patients progress to serious manifestations of neurologic, hemorrhagic, cardiovascular, and renal involvement. Severe infection is associated with

• neurological symptoms (confusion, ataxia, tremors, progressing to convulsions and coma)

• hemorrhagic manifestation resulting from thrombocytopenia includes hematomas, blood in vomit, urine; bleeding from gums, rose, vagina, and GI tract.

• Secondary bacterial infections, especially pneumonia and septicemia are common and complicate recovery