Lassa Fever: Transmission, symptoms, prevention, treatment as NCDC declares national emergency

Last month, March 2023, the Nigeria Center for Disease Control (NCDC) declared a national emergency on Lassa fever. Dr Ifedayo Adediba, the organisation’s Director General, said the emergency was declared after a risk assessment and increased reported cases of people with the ailment. 

In its Lassa Fever situation report, the agency said it had recorded 104 deaths from the virus this year,  from 636 cases across 22 states, confirming the resurgence of the virus. 

What is Lassa Fever?

Lassa fever is an animal-borne viral hemorrhagic fever first identified in Lassa, Borno State, Northern Nigeria, in 1969. The virus is endemic in parts of West Africa, including Liberia, Sierra Leone, Guinea and Nigeria, and is caused by the Lassa virus, which belongs to the family Arenavirus

Lassa fever is transmitted to humans through contact with infected rodents or their excreta and for medical personnel, through direct contact with the bodily fluids of infected humans.

National Emergency on Lassa Fever: what does that mean?

According to Dr Sandra Mba, Lassa Fever Incident Officer at the NCDC, when the National emergency is declared, the technical working group is converted and expanded into a National multi-sectoral emergency operational centre, which coordinates and works to strengthen the response to Lassa Fever in the country. 

Dr Mba held that the national emergency on Lassa fever was declared after a risk assessment showed the country was at a high risk of increased Lassa fever transmission. She added that the declaration of a national emergency would allow for a multi-pronged approach to combat the virus, as the EOC will draw from the resources of other government agencies like the Ministry of Agriculture and Rural Development, Ministry of Environment, and even private sector partners. 


Lassa Fever can be transmitted in the following ways:

1. Contact with infected rodents: Humans become infected with the Lassa virus primarily from exposure and contact with the urine, faeces, saliva, or blood of infected Mastomys rats, which are common in West Africa. 

2. Person-to-person transmission: The virus can be transmitted from one person to another through direct contact with the blood, urine, saliva, or other bodily fluids of an infected person.

3. Contact with contaminated objects: The virus can also be transmitted through contact with objects contaminated with the virus, such as bedding, clothing, or medical equipment.

4. Consumption of contaminated food: Eating food contaminated with the urine or faeces of infected rodents can also lead to virus transmission.

5. Aerosol transmission: There is also evidence of airborne transmission of the virus, particularly in laboratory settings.


About eight in ten persons who get the virus have no symptoms, and when there are symptoms, it usually appears one to three weeks after infection and can range from mild to severe. 

The initial symptoms include fever, headache, muscle aches, sore throat, cough and general weakness. These symptoms are like many other common illnesses, so diagnosing Lassa fever in its early stages is difficult.

As the disease progresses, more severe symptoms may develop, including abdominal pain, vomiting, diarrhoea, respiratory distress, and bleeding from the mouth, nose, and other body parts. In severe cases, Lassa fever can lead to shock, organ failure, and death.

Risk factors

Several factors increase one’s risk of contracting Lassa fever. These include:

1. Living in or travelling to endemic areas: Since the virus is endemic to the West African subcontinent, people living in this area or who frequently travel to the area stand an increased risk of infection.

2. Contact with rodents: The primary mode of virus transmission is contact with rodents or their excrement. People who work with rodents, such as farmers or laboratory workers, are at increased risk of infection. 

3. Direct contact with bodily fluids: Health care workers and family members of infected persons stand an increased risk of infection as the Lassa virus can also be transmitted from person to person through contact with blood, urine, or other bodily fluids of an infected person. 

Prevention and Control

Preventing Lassa fever requires a multi-faceted approach. The following measures can help reduce the risk of infection:

1. Avoid contact with rodents: The primary transmission mode of the Lassa virus is contact with rodents or their excreta. Therefore, avoiding contact with rodents and keeping food and water sources out of their reach is important.

2. Practice good hygiene: Regular hand washing with soap and water can help prevent the spread of the Lassa virus. Keeping living areas clean and free of rodent infestations is also important.

3. Use protective clothing: When handling rodents or their excreta, it is important to wear protective clothing, such as gloves, masks, and goggles, to prevent contact with bodily fluids.

4. Educate the public: Raising public awareness about Lassa fever and its transmission can help prevent disease outbreaks. This can include educational campaigns on hand washing, rodent control, and safe food handling practices.

5. Control rodent populations: Reducing rodent populations through traps and rodenticides can help reduce the risk of Lassa fever transmission.


There is no specific treatment for Lassa fever, and management is mainly supportive. Patients with severe cases may require hospitalisation and supportive care, such as fluid and electrolyte replacement, oxygen therapy, and blood transfusions.

Antiviral medications, such as ribavirin, have shown some efficacy in treating Lassa fever early in the disease. However, the effectiveness of antiviral therapy is uncertain.

In addition to supportive care, managing any complications that may arise is important. For example, patients with bleeding may require transfusions of blood or blood products, while those with respiratory distress may require mechanical ventilation.


Lassa fever is a serious viral hemorrhagic fever endemic in parts of West Africa. The disease is transmitted to humans through contact with infected rodents or their excreta or through direct contact with the bodily fluids of infected humans. The symptoms of Lassa fever can range from mild to severe and can include fever, headache, muscle aches, sore throat, cough, and general weakness. 

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