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(bacterium or virus).
Lassa fever is an acute viral illness that occurs in west Africa. The illness was discovered in the year 1969 when two missionary nurses died from it in Nigeria. The virus is named after the town in
Nigeria where the illness first occurred. The virus is a member of the virus family, 'Arenaviridae,' and is a single-stranded RNA virus; it is, 'zoonotic,' or animal-borne. Lassa fever is endemic in parts of west Africa, to include the following areas:
• Sierra Leone
The animal carrier is the, 'multimammate rat,' or, 'Mastomys natalensis,' which is distributed throughout the region as a whole.
The number of people who experience Lassa fever each year in west Africa is estimated to be between 100,000 and 300,000, with around 5,000 people dying from the virus. The estimates are crude because surveillance for cases of the disease is not performed uniformly.
Facts: Transmission Of Lassa Fever
While most humans are infected either from contact with an infected rat or inhalation of air contaminated with rat excretions, like other hemorrhagic fevers, Lassa fever can be transmitted directly from one human to another. It can be contracted through direct contact with infected human blood excretions and secretions, including through sexual contact. No evidence of airborne transmission person-to-person is seen. Transmission through Bre@st milk has also been observed.
Signs and Symptoms of Lassa Fever
The signs and symptoms of Lassa fever commonly happen 1-3 weeks after a person has come into contact with the virus. For most of those with a Lassa fever virus infection; around 80%, symptoms are mild and under-diagnosed. Mild symptoms include:
• Slight fever
• General malaise
Around 20% of infected people; however, the disease might progress to more serious symptoms that include hemorrhaging of the person's eyes, gums, or nose - repeated vomiting, respiratory distress, pain in the back, chest and abdomen, facial swelling and shock. Neurological issues have also been described in relation to Lassa fever, to include tremors, hearing loss and encephalitis. An infected person may die within two weeks of their initial symptoms because of multi-organ failure.
The most common complication of Lassa fever is deafness. Different degrees of deafness happen in around one-third of those who become infected. In many cases, the hearing loss is permanent. The severity of the disease does not affect this particular complication; deafness might develop in mild as well as severe cases.
Between 15-20% of people who are hospitalized for Lassa fever die from the illness. Only 1% of all Lassa virus infections; however, result in the person's death. The death rates for women in the third trimester of pregnancy are exceptionally high. Spontaneous abortion is a very serious complication of the infection; an estimated 95% mortality rate in fetuses of infected mothers is an alarm sounding off. Due to the fact that the symptoms of Lassa fever are so nonspecific and varied, clinical diagnosis is often times difficult. Lassa fever is also associated with occasional epidemics. During these epidemics, the fatality rate may reach as high as 50% in people who become hospitalized.
Preventing Lassa Fever
Primary transmission of the Lassa virus from its host to people may be prevented by avoiding contact with Mastomys rats - particularly in the geographic areas where outbreaks happen. Putting food away in rat-proof containers and keeping your home clean help with discouraging rats from entering your home. Using these rats as a source of food is definitely not recommended. Trapping around and in homes may help to reduce rat populations. Yet the wide distribution of Mastomys rats in Africa makes complete control of these rats impractical.
While providing care for people with Lassa fever, further transmission of the disease through person-to-person contact or other routes may be avoided by taking preventative precautions against contact with secretions from infected persons called, 'VHG isolation precautions,' or barrier nursing methods. The precautions include wearing protective clothing such as masks, gowns, gloves and goggles; using infection control measures such as the sterilization of equipment. It is vital to isolate infected people from contact with unprotected persons until the disease has run its course.
In addition, educating people who live in high-risk areas about ways to lower the rat populations in their homes will help to control and prevent Lassa fever. Other challenges include the development of quicker diagnostic tests and increasing the availability of the one drug known for treatment of Lassa fever - ribavirin. Research is currently being performed in regards to the development of a vaccine for the illness.