With the trend of things now, the fear of Lassa fever seems to be the beginning of wisdom. And despite the assurances from the Federal Government that all is well, many have continued to live in fear and rightly so as the available statistics of cases are staggering. There have been confirmed cases in Bauchi, Ebonyi, Edo, Enugu, Kano, Nasarawa, Ogun, Rivers, and Taraba states with recorded deaths in Imo, Kogi, Ondo and Plateau states among others.
The disease which got its name from Lassa, a village in Borno State where it was first identified in 1969, occurs more in the dry season than in the rainy season. It is caused by a species of rodents called the Natal multimammate rat, the common African rat, or the African soft-furred rat. The Lassa virus is transmitted when the droppings, that is the urine or faeces of the rat – the natural reservoir for the virus – comes in contact with foodstuffs or in the process of the rat accessing grain stores, either in silos or in residences.
The rodents live in houses with humans and deposit excreta on floors, tables, beds and food. Consequently the virus is transmitted to humans through cuts and scratches, or inhaled via dust particles in the air. In some regions these rodents are also consumed as food. Secondary transmission of the virus between humans occurs through direct contact with infected blood or bodily secretions. This occurs mainly between individuals caring for sick patients, although anyone who comes into close contact with a person carrying the virus is at risk of infection. Nosocomial transmission, that is the transmission that occurs as a result of treatment in a hospital and outbreaks in healthcare facilities in endemic areas represents a significant burden on the healthcare system due to the high infectivity, morbidity and mortality associated with it.
In the early stages, Lassa fever is often misdiagnosed as common cold, typhoid or malaria, and as a result, many patients fail to receive appropriate medical treatment. Making a correct diagnosis of Lassa fever is made difficult by the wide spectrum of clinical effects that manifest, ranging from asymptomatic to multi-organ system failure and death. The onset of the illness is typically mild, with no specific symptoms that would distinguish it from other febrile illnesses. In 80 per cent of cases, the disease is without symptoms but in the remaining 20 per cent, it takes a complicated course. It has an incubation period of six to 21 days after which an acute illness develops.
Early signs include fever, headache and general body weakness, followed by sore throat, nausea, vomiting, abdominal pain and diarrhoea in some cases. After four to seven days, many patients will start to feel better, but a small minority will present with multi-organ involvement. It can affect the gastro intestinal tract causing nausea, vomiting and stooling of blood as well as difficulty in swallowing; cardiovascular system symptoms include hypertension or hypotension as well as abnormal high heart rate and shock. In the respiratory tract, the victim experiences chest pains, cough and difficulty in breathing. The virus also causes difficulty in hearing, meningitis and seizures. Other symptoms include oedema, hypertension, bleeding and shock. Death from Lassa fever most commonly occurs 10 to 14 days after symptom onset. Non-specific symptoms are facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding. And one of the hallmarks of Lassa virus infection is the absence of functional antibodies during acute infection.
As mentioned earlier, clinical diagnosis of Lassa fever infections is difficult to distinguish from other viral haemorrhagic fevers such as Ebola and from more common febrile illnesses such as malaria, but, 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. Reverse transcription – PCR (RT-PCR) is routinely used for confirmation of cases. The virus is excreted in urine for 3- 9 weeks and in semen for three months. No vaccine for Lassa fever is currently available for use in humans.
There are three ways by which the virus can be treated and also prevented from further spread. These are implementation of barrier nursing, which is isolation of victims, tracing of people that have come in contact with sufferers as well as the initiation of treatment with the only available drug, Ribavirin. The latter is only effective if administered early, within the first six days after disease onset.
Therefore, it is essential that preventive measures be put in place to prevent this fatal disease. Firstly, the primary source of transmitting the disease to humans should be prevented. This can be possible through avoiding contact with 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 population.