HOST OF LASSA VIRUS
The reservoir, or host, of Lassa virus is a rodent known as the "multimammate rat" of the genus Mastomys. It is not certain which species of Mastomys are associated with Lassa; however, at least two species carry the virus in Sierra Leone. Mastomys rodents breed very frequently, produce large numbers of offspring, and are numerous in the savannas and forests of West, Central, and East Africa. In addition, Mastomys generally readily colonize human homes. All these factors together contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.Like other hemorrhagic fevers, Lassa fever can be transmitted directly from one human to another. It can be contracted by an airborne route or with direct contact with infected human blood, urine, or semen. Transmission through breast milk has also been observed.
HOW CAN LASSA FEVER BE PREVENTED?
-Avoid contact between rats and human beings;
-Keep your house and Environmnt clean.
-Cover all foods and water properly.
-Cook all foods thoroughly
-Block all rat hideouts
-Do not spread food where rats can have access to it.
-And as soon as you suspect Lassa fever, or you have persistent fever not responding to the standard treatment for malaria and typhoid, report to the nearest Health facility.
SYMPTOMS
In 80% of cases the disease is inapparent, but in the remaining 20% it takes a complicated course. It is estimated that the virus is responsible for about 5,000 deaths annually. The fever accounts for up to one third of deaths in hospitals within the affected regions and 10 to 16% of total cases.After an incubation period of six to twenty-one days, an acute illness with multiorgan involvement develops. Non-specific symptoms include fever, facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding. The other symptoms arising from the affected organs are:
Gastrointestinal tract
-Nausea
-Vomiting (bloody)
-Diarrhea (bloody)
-Stomach ache
-Constipation
-Dysphagia (difficulty swallowing)
-Hepatitis
Cardiovascular system
-Pericarditis
-Hypertension
-Hypotension
-Tachycardia (abnormally high heart rate)
Respiratory tract
-Cough
-Chest pain
-Dyspnoea
-Pharyngitis
-Pleuritis
-Nervous system
-Encephalitis
-Meningitis
-Unilateral or bilateral hearing deficit
-Seizures
Clinically, Lassa fever infections are difficult to distinguish from other viral hemorrhagic fevers such as Ebola and Marburg, and from more common febrile illnesses such as malaria.
The virus is excreted in urine for three to nine weeks and in semen for three months.
DIAGNOSIS
Lassa fever is most often diagnosed by using enzyme-linked immunosorbent serologic assays (ELISA), which detect IgM and IgG antibodies as well as Lassa antigen. The virus itself may be cultured in 7 to 10 days. Immunohistochemistry performed on tissue specimens can be used to make a post-mortem diagnosis. The virus can also be detected by reverse transcription-polymerase chain reaction (RT-PCR); however, this method is primarily a research too.
TREATMENT
All persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of.Early and aggressive treatment using Ribavirin was pioneered by Joe McCormick in 1979. After extensive testing, it was determined that early administration is critical to success. Additionally, Ribavirin is almost twice as effective when given intravenously as when taken by mouth. Ribavirin is a prodrug which appears to interfere with viral replication by inhibiting RNA-dependent nucleic acid synthesis, although the precise mechanism of action is disputed.The drug is relatively inexpensive, but the cost of the drug is still very high for many of those in West African states. Fluid replacement, blood transfusion and fighting hypotension are usually required. Intravenous interferon therapy has also been used.
When Lassa fever infects pregnant women late in their third trimester, it is necessary to induce delivery for the mother to have a good chance of survival.This is because the virus has an affinity for the placenta and other highly vascular tissues. The fetus has only a one in ten chance of survival no matter what course of action is taken; hence focus is always on saving the life of the mother. Following delivery, women should receive the same treatment as other Lassa fever patients.Siga Technologies is developing an antiviral drug that has been shown effective in treating experimentally infected guinea pigs. In a study conducted at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), treatment with ST-193 once a day for 14 days resulted in significant reduction in mortality (71% of the animals survived at the low dose), whereas all untreated animals and those treated with ribavirin died within 20 days of the infection.Due to threat of disease being used as a potential military weapon, a vaccine to reverse the disease is still being worked on.As serious as the disease is, there are numerous accounts of survival. However, there have been last affects of the disease.
COMPLICATION.
The most common complication of Lassa fever is deafness. Various degrees of deafness occur in approximately one-third of cases, and in many cases hearing loss is permanent. As far as is known, severity of the disease does not affect this complication: deafness may develop in mild as well as in severe cases. Spontaneous abortion is another serious complication.
PROPORTION OF PEOPLE WHO DIE
Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. 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.
