Lassa fever in Nigeria

Level 1 - Practise health precautions (more details)

Original publication date: February 16, 2023

Updated: April 5, 2023

Current situation

Nigeria is currently experiencing a large outbreak of Lassa fever. The number of cases usually increases during the dry season, between December and March. Confirmed cases have been reported in several states. Edo and Ondo states have reported the highest number of cases.

For the latest updates on Lassa fever in Nigeria, including the total number of cases and deaths, please visit the Nigerian Centre for Disease Control’s website.

Lassa fever

Lassa fever is caused by the Lassa virus. Lassa virus is most commonly spread through the urine and droppings of infected rats.

This includes:

  • direct contact with rat urine or droppings, particularly to open cuts or sores
  • touching contaminated objects or eating contaminated food
  • inhaling dust particles of rodent droppings (which can happen during cleaning activities like sweeping or dusting)

Lassa virus can also be spread from person-to-person by direct contact with the blood, tissue, urine, or other body fluids of a person infected with Lassa fever.

The risk is low for most travellers. Those who are most at risk of getting Lassa fever are those who:

  • live or work in areas with a risk of Lassa fever and have been exposed directly or indirectly to infected rats
  • provide care for patients in a community where the illness is present

In about 80% of people infected with the Lassa virus, the illness is mild or there are no noticeable symptoms. However, in 20% of infected individuals the disease can result in severe illness and hospitalization.

Symptoms usually begin 7 to 10 days after exposure. They usually last for about 16 days, although a range of 6 to 30 days is possible. Symptoms include:

  • fever
  • diarrhea
  • vomiting
  • headache
  • chest pain
  • facial swelling
  • abdominal pain
  • sore throat and cough
  • bleeding from nose or mouth

The virus can result in significant internal bleeding and organ failure.

Permanent hearing loss can be a result of the virus.

The disease is especially severe during late pregnancy when maternal death and fetal loss frequently occurs, particularly during the third trimester.

Symptoms of Lassa fever are similar to those of other viral haemorrhagic fevers and infectious diseases like malaria or typhoid. They affect the vascular system, which controls how blood moves through the body.

There is no vaccine or medication that protects against Lassa fever.


Before your trip

Consult a health care professional or visit a travel health clinic preferably at least 6 weeks before you travel.

During your trip

You can reduce the risk of becoming infected with or spreading Lassa fever by:

  • avoiding contact with rodents (rats), especially rat urine and droppings
    • store food in rodent-proof containers
    • dispose of garbage far from your living quarters
    • maintain clean living quarters
    • do not eat rats
    • ensure that food is well cooked
    • if it is necessary to clean areas contaminated by rat urine or feces, follow proper safety precautions
  • washing your handsfrequently with soap and water for at least 20 seconds
    • if soap and water are not available, use hand sanitizer containing at least 60% alcohol
  • keeping your hands away from your face
  • avoiding shared eating or drinking utensils
  • cleaning and disinfecting high-tough surfaces and objects
  • avoiding close contact with people with Lassa fever, and their body fluids
  • practicing safe sex

Health care workers should follow strict infection control measures. This includes wearing all necessary personal protective equipment such as masks, gloves, gowns, and face shields when caring for patients with suspected or confirmed Lassa fever.

Monitor your health

If you develop symptoms of Lassa fever when you are travelling or after returning home, call a health care professional immediately. Make sure to tell them your full travel history. Describe your symptoms over the phone before your appointment. This is so that health care staff can arrange to see you without exposing themselves or others to your illness. The sooner you get treatment, the better your chances are for recovery.

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