The disease called Lassa

BY PRISCILLA CHRISTOPHER

Another potent epidemic claiming lives without warning has broken loose among us. It is known as Lassa fever or Lassa hemorrhagic fever (LHF); an acute viral hemorrhagic fever caused by the Lassa virus which was first discovered in the town of Lassa, in Borno State when two missionary nurses died in 1969. A member of the Arenaviridae virus family, Lassa Fever is found in African countries like Nigeria, Liberia, Sierra Leone, Guinea, and the Central African Republic. 

The primary animal host of the virus is the Natal multimammate mouse, an animal found in most of sub-Saharan Africa. This is probably the most common mouse in equatorial Africa, ubiquitous in human households and eaten as a delicacy in some areas. 

The virus, we are told is shed in the urine droppings of these rats and can be transmitted through direct contact, touching objects and eating food contaminated with these materials or through cuts and sores. Person to person transmission also occurs most especially when a person comes in contact with the virus in the blood, tissue, secretions or excrement of an infected individual.

Infection in humans typically occurs by exposure to animal excrement through the respiratory or gastrointestinal tracts. Inhalation of tiny particles of infectious material (aerosol) is believed to be the most significant means of exposure. It is possible to acquire the infection through broken skin or mucous membranes that are directly exposed to infectious material. Transmission from person to person has also been established, presenting a disease risk for healthcare workers. Frequency of transmission by sexual contact has not been established.

Early symptoms of the disease include fever, headache, chills, diarrhea, nausea, vomiting, sore throat, backache and joint pains but 80% of people who become infected with Lassa virus have no symptoms. In severe cases, there is facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina, gastrointestinal tract and low blood pressure. Some 25% of patients that survive the disease end up deaf, in about half of these, the hearing returns partially after 3 months. There is some hair loss and gait disturbance that occurs during the recovery period while late symptoms include bleeding from the eyes, ear, nose, bleeding from the mouth and rectum, eye swelling, swelling of the genitals and rashes all over the body that often contains blood. The later stages of Lassa fever are shock, seizures, tremor, disorientation and coma. Death occurs within 14 days. Early supportive care with rehydration and symptomatic treatment improves the survival rate of the patients of Lassa fever. 

The incubation period for Lassa fever is 21 days. Therefore, if a person is suspected to have the disease, he will be put in an isolation room for 21 days in order to confirm if he/she has the disease or not.

Since its upsurge in 1969, the deadly disease had infected persons in 26 States. In 2005 in Ebonyi State, 5 nurses lost their lives to Lassa fever in the course of duty; 6 cases were reported in the state in 2008 while 2 doctors died while treating the infected medical personnel. In 2011, there were 7 cases and 2 deaths. In 2012, there were 20 cases and 6 deaths. In 2013, there were 21 cases and 8 deaths. The Federal Ministry of Health said that the number of cases peaked in 2012 when 1, 732 cases were discovered nationwide resulting in 112 fatalities. In 2012, Lassa fever spread to 12 States in Nigeria and killed 40 people. 397 suspected cases have been recorded in another 12 States: Borno, Gombe, Yobe, Taraba, Plateau, Nasarawa, Edo, Ondo, Rivers, Anambra and Lagos. Eight doctors and three nurses contracted Lassa fever from a pregnant woman in Ebonyi State in 2014 on whom they performed surgery and as at this year, the states affected are Bauchi, Nasarawa, Niger, Taraba, Kano, Ebonyi, Rivers, Edo, Plateau, Gombe and Oyo, Ogun and Lagos State. 

According to a release by the Ministry of Health recently, in the last 6 weeks, Nigeria has been experiencing Lassa fever (LF) outbreak which has so far affected more than 8 states.  The total number of suspected cases so far reported is 76 with 35 deaths, and a Case Fatality Rate (CFR) of 46%. The Ministry of Health laboratories have confirmed 14 cases, indicative of a new episode of Lassa fever outbreak. 

The goodnews however is, Lassa can be treated with an antiviral drug called Ribavirin but it must be administered early. 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. 

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.

In the face of the fight to arrest the situation, Nigerians are advised and instructed to take precautionary measures such as stopping bush burning so that they don’t drive the rats into close-by houses. Doctors caring for patients with Lassa fever should also monitor fluid, electrolyte and oxygen levels of the patients because there is no vaccine for that. Family members and health care workers are also advised to always be careful and avoid contact with blood and body fluids while caring for sick persons with symptoms similar to those listed for Lassa fever and any such patients should be taken to nearest health facility.

Control of the Mastomys rodent population is impractical, so measures are limited to keeping rodents out of homes and food supplies, as well as maintaining effective personal hygiene. Gloves, masks, laboratory coats, and goggles are advised while in contact with an infected person. All persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of.

It has been discovered that someone could also be infected from the fluid or blood of an infected person and by shaking hands with people who are seriously infected hence, such undue courtesy should be avoided for the time being. Other preventive measures include: ensuring that food is properly covered, either cooked or uncooked. Liquid soap and antiseptics should be used to wash the hands, rules of regular hand-washing should be adhered to always, Rodenticides  should be used to kill rats, while the bush around the home should be cleared regularly. The windows and doors of the house should be closed especially when it is night time.

Anybody who shows the given symptoms above should report to the hospital immediately in order to prevent people not infected from coming up with the disease.
In addition, all efforts should be geared towards maintaining a general personal, home and environmental cleanliness.