Dr Ige O. T. is the Chairperson, BDTH – Infectious Disease Control Committee, HOD Microbiology Department in the Teaching Hospital, and a Senior Lecture at Kaduna State University, Kaduna Nigeria.
Lassa fever is an acute viral haemorrhagic fever illness of 2-21 days duration that is known to be endemic in various West African countries including Nigeria. The Lassa virus is transmitted to humans via contact with food or household items contaminated with Mastomys rodent urine or faeces. Person-to-person transmission occurs in both community and health-care settings, where the virus may be spread by contaminated medical equipment, such as re-used needles. Laboratory transmission can also occur, particularly in hospitals lacking adequate infection prevention and control measures. A total number of 258 confirmed Lassa fever cases have been recorded in Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Kaduna and Lagos States. The total number of deaths recorded is 41, 5 health care workers have been affected. Early supportive care with rehydration and symptomatic treatment improves survival.
About 80% of the human infection is symptomless. The onset of the disease, when it is symptomatic, may begin gradually with non-specific symptoms such as fever, malaise, followed by severe headache sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. In severe cases facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop. The victim may also present with conjunctivitis, pharyngitis, tonsillitis and prostration. Protein may be noted in the urine. Shock, seizures, tremor, disorientation, and coma may be seen in the later stages. Deafness occurs in 25% of patients who survive the disease.
Lassa virus infections can only be diagnosed definitively in the laboratory using the following tests:
(a) Reverse transcriptase polymerase chain reaction (RT-PCR) assay
(b) Antibody enzyme-linked immunosorbent assay (ELISA)
(c) Antigen detection tests virus isolation by cell culture. The diagnosis via the RT-PCR is available for suspected cases in Kaduna State
The drug of choice for the management of Lassa Fever is ribavirin. The drug reduces the mortality rate of the infection, if treatment is started early and last for adequate duration of 10 days. Symptomatic supportive treatment is also needed.
PREVENTION AND CONTROL
a) Prevention of Lassa fever relies on promoting good “community hygiene” to discourage rodents from entering homes. Effective measures include storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, maintaining clean households and keeping cats. Because Mastomys are so abundant in endemic areas, it is not possible to completely eliminate them from the environment. Family members should always be careful to avoid contact with blood and body fluids while caring for sick persons.
b) In health-care settings, staff should always apply standard infection prevention and control precautions when caring for patients, regardless of their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal protective equipment (to block splashes or other contact with infected materials), safe injection practices and safe burial practices.
c) Health-care workers caring for patients with suspected or confirmed Lassa fever should apply extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding. When in close contact (within 1 metre) of patients with Lassa fever, health-care workers should wear face protection (a face shield or a medical mask and goggles), an overall body suit and gloves (sterile gloves for some procedures). Additional transmission-based precautions will be necessary and enforced for these group of health-care workers too.
d) Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Lassa virus infection should be handled by trained staff and processed in suitably equipped laboratories under maximum biological containment conditions. All laboratorians must adhere strictly to standard precaution.