Lassa fever: information sheet for category 3 contacts
Advice for people who have come into contact with Lassa virus.
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You have been given this information sheet because you have had contact with someone infected with Lassa virus, or materials contaminated with Lassa virus. Lassa virus causes a disease called Lassa fever. You should follow the advice in this information sheet and check yourself for symptoms for 21 days after your last possible contact with Lassa virus. If you develop symptoms of Lassa fever within 21 days of your last exposure to Lassa virus, you should stay at home and call your designated contact immediately.
About Lassa fever
Lassa fever is a rare but serious disease caused by Lassa virus. Lassa virus is endemic in parts of West Africa, particularly Guinea, Liberia, Nigeria and Sierra Leone.
How Lassa virus spreads
Lassa virus can spread by:
- direct contact with the organs, blood, secretions, or other bodily fluids of an infected person, for example their vomit, faeces, urine, saliva, or semen (including through sexual transmission)
- contact with objects, such as needles or soiled clothing, that have been contaminated with infected bodily fluids
- contact with infected rodents
Lassa virus is not spread through routine, social contact (such as shaking hands or sitting next to someone) with people who do not have symptoms. There is no evidence that Lassa virus can spread through the air.
It takes up to 21 days from when someone is exposed to the virus for symptoms to appear.
Symptoms of Lassa fever
Lassa virus infection causes only mild or no symptoms in approximately 80% of those infected. When symptoms occur, they range from mild fever with sore throat, to chest pain and later bleeding.
The illness begins with:
- fever (temperature above 37.5°C)
- headache
- sore throat
- generalised aches and feeling unwell
This can be accompanied by:
- cough
- nausea
- vomiting
- diarrhoea
- chest and abdominal pain
- sore, swollen or red eyes
Fever can occur constantly or in peaks. Inflammation of the throat and eyes is common. In some cases, the tonsils and throat become inflamed with white patches and small ulcers. Overall, only about 1% of infections result in death.
Preventing and treating Lassa fever
There is currently no licensed vaccine for Lassa virus. To avoid Lassa virus spreading between people, those caring for individuals with possible or suspected Lassa fever should avoid contact with the patient’s bodily fluids and should wear personal protective equipment (PPE).
Treatment for Lassa fever is with supportive care, including balancing fluids and electrolytes, maintaining the patient’s oxygen status and blood pressure, and treating any other infections they may have at the same time. There are antiviral drugs which, if used early on after the start of symptoms may make the illness less serious for anyone infected. They do not prevent the illness altogether.
Your risk of developing Lassa fever
You reported that you were in the same room as, and within 2 metres of, someone who had Lassa fever, but you did not have direct contact with them, their body fluids or objects that they may have contaminated.
We would like to monitor you for a period of 21 days from when you were last exposed to Lassa virus. This will mean that we can act quickly in the unlikely event that you develop symptoms, reducing the risks to you and to others close to you.
What you need to do
Your family and household contacts are not at risk of catching Lassa virus from you if you do not have any symptoms.
You should take the following actions for 21 days from when you were last exposed to Lassa virus:
- record your temperature and monitor yourself for other symptoms suggestive of Lassa fever (as listed above) twice per day at the same times each day
- report to your designated contact if you develop a temperature of 37.5°C or higher, or other symptoms suggestive of Lassa fever, so that they can arrange for you to be assessed. They will explain the local arrangements for accessing healthcare
- there are no restrictions on work, travel or social activities as long as you have no symptoms
- do not share towels, bed linen, toothbrushes or razors as a precaution
- use barrier contraception or avoid unprotected sexual contact with other people as a precaution
- postpone any non-essential medical or dental treatment including vaccination. If you need essential medical or dental treatment, inform your healthcare provider about your possible contact with Lassa virus
If you are a healthcare worker, you should tell your line manager that you have been identified as a contact of Lassa virus, but that you are still able to attend work as long as you remain asymptomatic.
Use of medicines such as aspirin, paracetamol or ibuprofen
Certain medicines, such as paracetamol, ibuprofen and aspirin, can reduce your body temperature during a fever (antipyretic) for up to 8 hours. Thermometer measurements may therefore show a lower temperature than would be expected for up to 8 hours after taking an antipyretic.
You must call your designated contact for further advice if you need to take an antipyretic medicine.
Please take your temperature before you take paracetamol, ibuprofen or aspirin. If your temperature is 37.5°C or higher, you must call your contact immediately.
A temperature of 37.5°C or higher is always significant, whether you are taking one of these medicines or not, and must be reported urgently.
What to do if you become ill
It is unlikely that you have caught Lassa virus. However, if you are feeling unwell or develop any of the symptoms of Lassa fever (including a temperature of 37.5°C or higher) within 21 days from when you had contact with Lassa virus, please stay at home. Take your temperature if you have not done this already. Phone your designated contact immediately, who will arrange for you to be assessed by an appropriate clinician. In an emergency, you should call 999 and tell them about your symptoms and possible contact with Lassa virus.
Further information
More information about Lassa fever can be found at:
- UK Health Security Agency: Lassa fever: origins, reservoirs, transmission and guidelines
- World Health Organization: Lassa fever