Lassa fever

Lassa virus is carried by the multimammate rat, which often lives in and around homes in endemic regions. TravelHealthPro explains that the virus usually spreads from these rats to humans by direct contact with the rats' urine and faeces or through contaminated surfaces and food. Person-to-person spread can also occur through the body fluids of an infected person, including blood, faeces, saliva, urine, semen and vomit, which is why healthcare workers and carers are at risk without adequate protection.

The disease is concentrated in countries such as Guinea, Liberia, Nigeria and Sierra Leone, with occasional cases in neighbouring areas. Cases rise in some seasons when rodents move closer to dwellings.

Most people who are infected have no symptoms or mild illness. Early features are fever, tiredness, headache, muscle aches and a sore throat. In severe disease, TravelHealthPro notes bleeding from the mouth, nose or gastrointestinal tract can occur, and breathing, kidney and brain involvement may follow. Hearing loss is a recognised complication in survivors.

TravelHealthPro states that approximately 20 per cent of infections are severe, with about 1 per cent fatality overall. Pregnancy is particularly dangerous: it reports mother and/or foetal deaths in more than 80 per cent of cases during the third trimester, which is why pregnant women in or travelling to endemic areas need individual advice.

• Gradual onset of fever, weakness and malaise.

• Sore throat, headache, muscle and chest pain.

• Vomiting, diarrhoea and abdominal pain.

• In severe cases bleeding, swelling of the face, low blood pressure and organ failure.

In the UK a person with fever after travel to an endemic area is assessed urgently, with malaria excluded first because it is the commonest and most treatable cause. If Lassa fever is considered possible after risk assessment, UKHSA protocols for imported viral haemorrhagic fevers apply, including isolation, specialist laboratory testing and, where confirmed, care in a high-level isolation unit. These steps protect staff and others while the diagnosis is clarified.

Treatment is mainly supportive: careful fluid replacement, oxygen, blood products if needed and management of organ problems. TravelHealthPro notes that hydration and blood transfusions improve outcomes and that ribavirin may help if given early, although recent evidence questions its effectiveness.

There is no licensed vaccine. TravelHealthPro advises avoiding contact with infected people and rodent-contaminated areas, avoiding undercooked meat, maintaining hygiene, and using protection during sexual contact for three months after recovery. In endemic countries, storing food in sealed containers, keeping homes clean and controlling rodents are community measures.

TravelHealthPro describes the risk for tourists and most travellers as very low, and cases affect mainly people working in endemic areas, especially healthcare and humanitarian workers. UK cases have been identified in returning travellers from West Africa and are managed with national expertise. If you have travelled to an affected area and develop fever within about three weeks of return, tell NHS 111 or the clinician your travel history straight away.

Call 999 for severe breathlessness, bleeding, confusion or collapse. Contact NHS 111 or an emergency department promptly by phone first if you develop fever after recent travel to West Africa, so that arrangements can be made to protect others in a waiting room.