Saturday, January 9, 2010
An acute viral illness that is endemic in parts of West Africa (Guinea, Liberia, Sierra Leone and Nigeria). Caused by, Lassa Virus (family Arenaviridae), a single-stranded RNA virus and is zoonotic. The reservoir of Lassa virus is a rodent known as the "multimammate rat" of the genus Mastomys. Rodents shed the virus in urine and droppings.
Therefore, the virus can be transmitted through direct contact with these materials, through touching objects or eating food contaminated with these materials, or through cuts or sores. Also spread through person-to-person by contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus.
In some areas of Sierra Leone and Liberia, it is known that 10%-16% of people admitted to hospitals have Lassa fever.
Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. These include fever, retrosternal pain, sore throat, back pain, cough, abdominal pain, vomiting, diarrhea, conjunctivitis, facial swelling, proteinuria, and mucosal bleeding. Neurological problems have also been described, including hearing loss, tremors, and encephalitis.
Diagnosis is by detecting IgM and IgG antibodies as well as Lassa antigen by ELISA. The virus itself may be cultured in 7 to 10 days. Immunohistochemistry performed on tissue specimens can be used to make a postmortem diagnosis. The virus can also be detected by RT-PCR
Ribavirin has been used with success in Lassa fever patients. (most effective in the early course of the illness). The most common complication of Lassa fever is deafness- and in many cases hearing loss is permanent.
Approximately 15%-20% of patients die, can be as high as 50% in sever cases. However, overall only about 1% of infections with Lassa virus result in death. The death rates are particularly high for women in the third trimester of pregnancy, and for fetuses, about 95% of which die in the uterus of infected pregnant mothers.