Lassa fever: information sheet for category 5 contacts

You have been given this information sheet because you have had very close or direct contact with someone who is infected with Lassa virus, or material contaminated with Lassa virus. Lassa virus causes a disease called Lassa fever. You should stay at home and away from other people for 21 days after your last exposure to Lassa virus and regularly check yourself for symptoms of Lassa fever. If you develop symptoms of Lassa fever within 21 days of your last exposure to Lassa virus, 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 are a household or overnight contact of a confirmed symptomatic case

Or

• you have had significant exposure to material from a Lassa fever case, for example a needlestick injury or direct contact of mucous membranes or broken skin with a Lassa fever case or their body fluids (for example blood, vomit, faeces, urine, saliva) while they were symptomatic. This includes sexual contact

Because of your level of exposure, you are at risk of developing Lassa fever. We would therefore like to closely monitor you for a period of 21 days from when you were last exposed to Lassa virus. You should also carry out the actions listed below to minimise the risk to you and others close to you.  

What you need to do

Because you are at risk of developing Lassa fever, you should take the following actions for the 21 days from when you were last exposed to Lassa virus:

• self-isolate in private accommodation (unless an alternative arrangement has been agreed with UKHSA). See the information below on how to self-isolate
• record your temperature and monitor yourself for other symptoms suggestive of Lassa fever twice per day at the same times each day
• report these temperatures to your designated contact by 12 noon each day. They will want to know whether your temperature is below, equal to, or above 37.5°C, and will arrange further evaluation as necessary. They will explain the local arrangements for accessing healthcare
• if you become ill with any of the symptoms listed above in between reporting to your designated contact, you should phone your designated contact immediately. See below for further information on what to do if you become ill.

How to self-isolate

You should self-isolate for 21 days from when you were last exposed to Lassa virus. This means you should stay at home and not go to work, school or public areas. You should not travel, either within the UK or internationally.

You should self-isolate in a separate room from other members of your household, and avoid all contact with them, including sexual contact. You should sleep in a separate room to other people and use separate bathroom facilities for going to the toilet and for washing .

You should only leave your home if it is essential, for example in an emergency, or for urgent health and wellbeing issues. You should also not have visitors to your home. 

If you need help with groceries or other essentials, ask friends or family to drop your shopping off, or order online. Ask your friends, family or delivery drivers to leave your shopping at your front door to avoid contact with them.

Do not share items which you use, such as bedding, towels, wash cloths, toothbrushes, or razors. You should also use separate items for eating and drinking, such as cutlery, cups, or plates, to other people in your household. These measures are advised as a precaution to help protect others in case you are infected.

Postpone any non-essential medical or dental treatment. You should discuss any essential treatment required with your designated contact before attending a healthcare facility.

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, and 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

If you are feeling unwell or develop any of the symptoms of Lassa fever (including a temperature of 37.5°C or higher) , please remain 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. If there is any delay in making contact, phone 111 reporting your recent contact with someone with Lassa fever. In an emergency, you should call 999 and tell them about your symptoms and your recent 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