Lassa fever is a viral hemorrhagic fever caused by a rodent borne arena virus that is endemic in West Africa. It was first described in 1969 in a town called Lassa in Borno State, Nigeria.
It actually frequently infects people in West Africa (Liberia, Sierra Leone, Guinea, and the Central African Republic) resulting in 300,000- 500,000 cases annually and about 5,000 deaths each year. The Primary animal host is the multimammate mouse (Mastomys natalensis) and it’s found in most of SubSaharan Africa.
Virus is transmitted by contact with the feaces or urine of animals that have access to food stores in residences. Transmission may also occur from person to person when an individual makes contact with any tissue, blood excretions or secretions of an infected person, but casual contact will not spread the virus. Nosocomial transmission (transmission originating in a hospital) can also occur with contaminated needles or other medical equipment.
Signs and Symptoms
Symptoms begin one to three weeks after the initial infection and may include fever, back pain, abdominal pain, and sore throat, conjunctivitis swelling in the face, diarrhea, mucosal bleeding and proteinuria.
On occasion there have been reports of neurological issues such as tremors, encephalitis, and hearing loss. Symptoms can be very diverse making diagnosis challenging.
Diagnosis of Lassa fever requires laboratory testing. ELISA (enzyme-linked immunosorbent serological assays) is used to find Lassa antigen and antibodies. It takes about a week to culture the virus if its post-mortem tissue specimens are picked for immunochemistry.
Prognosis and Complications
Approximately 20% of hospitalized Lassa fever patients die from the disease. Death rate is especially high in pregnant women in their 3rd trimester. If a mother is infected, approximately 95% of the unborn fetuses die.
Deafness is a standard complication of Lassa fever and can occur in varying degrees in approximately a third of all cases. Permanent loss of hearing is typical and another grave complication already mentioned above is sudden abortion.
Treatment for Lassa fever requires an antiviral medication called Ribavirin. Ribavirin is especially effective in the early stages of Lassa fever.
Other supportive treatments required for a full recovery include maintaining blood pressure, Oxygenation, and Electrolyte and Fluid levels. If there are secondary infections arising these should be treated as well.
Prevention and understanding Risks
People living in areas with mastomys rodents are at high risk as well as medical workers in such areas, and so care must be taking to wear protective gear when treating patients.
Preventative measures include avoiding contact with rodents, keeping foods in rodent-proof receptacles, and practicing excellent hygiene of the person and the household. Do not consume rodents; pest control and extermination is recommended.
Practice proper equipment sterilization and keep infected individuals isolated from others until full recovery.
WHO does not advise or recommend any restrictions on travel or trade with Nigeria, but travellers returning from affected areas who develop symptoms of fever, malaise, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, and abdominal pain should seek medical advice.
The Federal and State governments are responding to the outbreak by enhancing the disease surveillance for early detection, reinforcing treatment of patients, and conducting awareness campaigns among the affected population.