Press Room

LASSA FEVER: All You Need To Know

With the recent outbreak of Lassa Fever in Nigeria, conscious steps need to be taken to curtail the spread of the virus and reduce mortality. The number of persons infected by the outbreak has increased to 86, while 40 deaths have been recorded in the affected states.

What is Lassa Fever?

Lassa fever or Lassa hemorrhagic fever (LHF) is an acute viral hemorrhagic fever caused by the Lassa virus and first described in 1969 in the town of Lassa, in Borno State, Nigeria. Lassa fever is a member of the Arenaviridae virus family.

Similar to ebola, clinical cases of the disease had been known for over a decade, but had not been connected with a viral pathogen.

Lassa frequently infects people in West Africa. It results in 300,000 to 500,000 cases annually and causes about 5,000 deaths each year. Outbreaks of the disease have been observed in Nigeria, Liberia, Sierra Leone, Guinea, and the Central African Republic.

The primary animal host of the Lassa virus is the Natal multimammate mouse (Mastomys natalensis), an animal found in most of sub-Saharan Africa. The virus is probably transmitted by contact with the feces or urine of animals accessing grain stores in residences. Given its high rate of incidence, Lassa fever is a major problem in affected countries.

Signs and Symptoms

Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. For the majority of Lassa fever virus infections (approximately 80%), symptoms are mild and are undiagnosed. Mild symptoms include slight fever, general malaise and weakness, and headache.

In 20% of infected individuals, however, disease may progress to more serious symptoms including hemorrhaging (in gums, eyes, or nose, as examples), respiratory distress, repeated vomiting, facial swelling, pain in the chest, back, and abdomen, and shock.

Neurological problems have also been described, including hearing loss, tremors, and encephalitis. Death may occur within two weeks after symptom onset due to multi-organ failure.

The most common complication of Lassa fever is deafness. Various degrees of deafness occur in approximately one-third of infections, 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.

Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, only 1% of all Lassa virus infections result in death. The death rates for women in the third trimester of pregnancy are particularly high. Spontaneous abortion is a serious complication of infection with an estimated 95% mortality in fetuses of infected pregnant mothers.

Because the symptoms of Lassa fever are so varied and nonspecific, clinical diagnosis is often difficult. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50% in hospitalized patients.

Prevention

Primary prevention involves avoidance of contact with rats. This tends to be heightened following bush burning. The rats are displaced from their natural habitat so they come close to homes in search of alternative abode.

Bushes and clutter around the house must be cleared to make the surrounding unattractive to rats.

Food, cooking utensils and drinking water must be kept in rat proof containers

Avoid using rats as food sources

To avoid human to human transmission:

-close contacts of individuals with illness involving fever that does not respond to treatment for malaria should wear gloves to touch body fluids.

-health workers must wear gloves, protective gowns and masks while caring for individuals suspected of Lassa fever.

-hospitalized suspected cases must be isolated and contact with staff of the hospital minimized: individualized equipment must be provided for such patients.

-separate thermometers, blood pressure apparatus, bath utensils etc. must be provided.

-specific team of health workers must be identified to care for suspected cases who must be nursed in isolation.

A high index of suspicion is required on the part of health workers for early detection and chance of curative treatment.

To escape the current acute viral illness called Lassa fever ravaging Nigeria, avoid any exposure to rats. The death percentage attributed to Lassa fever is currently put at 43.2 per cent, a rate considered very high by all standards.

Fact sheets released by the United States Centre for Disease Prevention and Control (US CDC) indicate that Lassa virus is carried by rats and spread to humans through contact with urine or droppings of infected rats in West Africa.

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, early administration was determined to be 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, induction of delivery is necessary 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, the focus is always on saving the life of the mother. Following delivery, women should receive the same treatment as other Lassa fever patients.

Work on a vaccine is continuing, with multiple approaches showing positive results in animal trials.

Reference: Wikipedia, The Nation

Leave a Reply