Outbreak status:
- The Nigerian Center for Disease Control and Prevention has activated Lassa Fever Emergency Operations Center for the year 2024 in response to the increasing risks of high transmission rates.
- On April 16th, 2023, there was an outbreak of Lassa fever higher than what was observed in 2022.
- In 2023, there were 1,279 confirmed cases, including 227 deaths. The total number of confirmed and probable cases reached 10,425 cases, and the mortality rate reached 17.9%.
- From January 1st to January 7th, 53 confirmed cases were monitored, including six deaths. The total number of confirmed and probable cases reached 243. The death rate was 11.3%.
About the disease:
Lassa fever is an acute viral hemorrhagic disease lasting 2 to 21 days that occurs in West Africa. It was named Lassa after the town of Lassa in Borno State, Nigeria, in 1969. The Lassa virus is part of the Arenavirus family, like the Ebola virus. Rats are the main carrier among those which carry this disease, especially the Natal rat (Mastomys natalensis), which is widespread in the Sahara Desert. These mice spread in grain stores, which in turn transmit it to humans.
Mode of transmission:
Humans usually become infected with Lassa virus because of exposure to the urine or feces of infected mice or rats. This virus may also spread to humans through direct contact with the blood, urine, feces, or other body secretions of a person infected with Lassa fever. There is no epidemiological evidence to support the spread of the disease through the air in humans. The infection is transmitted from person to person in the community and healthcare facilities, where the virus may spread through contaminated medical equipment such as reusable needles. Sexual transmission of Lassa virus has been reported.
Lassa fever occurs in all age groups and both sexes. The people most at risk of infection are people residing in rural areas, especially in communities that suffer from poor sanitation services. Health workers are at risk of contracting Lassa fever if they provide care to infected patients without taking appropriate health prevention measures and following appropriate infection prevention and control practices.
The incubation period: From 2 to 21 days
Symptoms:
Sensitivity to loud noise - high blood pressure - difficulty swallowing - constipation - stomach pain - bloody diarrhea - vomiting blood - nausea - fatigue - headache - shortness of breath - fever - muscle pain - sore throat - seizures - dull hearing.
Diagnosis:
- It is difficult to diagnose the condition based on clinical examination alone, as the symptoms are like other viral infections endemic in West Africa
- Specialized laboratory tests must be used, considering safety procedures when dealing with samples taken from the patient.
- Tests to detect antiviral antibodies and virus identifiers in the blood are used but are considered inaccurate.
- For accurate diagnosis, laboratory culture of the virus is used, a process that takes between a week and ten days.
- Polymerase chain reaction (PCR) gives faster and more accurate results, but its high cost limits its use and limits it to conducting scientific research.
Lassa fever treatment:
- Treatment initially focuses on supporting organ functions, such as raising blood pressure, lowering temperature, treating blood sodium disorders, and controlling a normal level of oxygen.
- The antiviral drug Ribavirin is used successfully in treating inflammation, especially if its use begins with the onset of symptoms of the disease.
- Studies have shown the ability of this drug to significantly reduce the death rate from 50 percent to about 5 percent.
Prevention:
There is no effective vaccine against the virus yet, and the effectiveness of taking ribavirin preventively to stop the spread of the disease in an epidemic manner has not been proven.
The best prevention methods are:
- Getting rid of rodents carrying the virus.
- Storing and preparing food healthily.
- Purifying and sterilizing drinking water.
- Health workers must also follow safety procedures while handling samples taken from patients to reduce the spread of the virus to them.
- Appropriate clothing must also be worn when mingling with infected patients, such as face masks, gloves, and a uniform that covers the entire body.
Travel restrictions:
WHO does not recommend any travel and/or trade restrictions to and from Nigeria based on the information in this report.
References:
World Health Organization (WHO)