Lassa fever is described as an acute viral haemorrhage illness that occurs in West Africa and last between two and 21 days.
It’s transmitted to humans via contact with food or household items contaminated with rodent urine or faeces.
While it’s not a new disease, the current outbreak is unprecedented and causing particular concern because the number of cases is unusually high for the time of year.
Dr Charlie Weller, head of vaccinations for the Wellcome Trust, offered information on everything he knows about Lassa fever to BBC.co.uk – the illness that currently has no vaccine.
Dr Weller said one of the hardest things about the disease is it’s difficult to treat.
He said: “Most people who catch Lassa will have only mild symptoms such as fever, headache and general weakness. They may have none at all.
“However, in severe cases, it can mimic another deadly hemorrhagic fever, Ebola, casing bleeding through the nose, mouth and other parts of the body.”
More than 1,000 suspected cases of Lassa have been reported across Nigeria since January, according to the country’s Centre for Disease Control.
The overall case-fatality is one per cent, but women who contract the disease late in pregnancy face an 80 per cent chance of losing their child, or dying themselves.
So what are the symptoms?
The World Health Organization says the onset of the disease, when it is symptomatic, is usually gradual, starting with fever, general weakness and malaise.
After a few days the following may develop:
- Sore throat
- Muscle pain
- Chest pain
- Abdominal pain
In severe cases the following may occur:
- Facial swelling
- Fluid in the lung cavity
- Bleeding from the mouth, nose, vagina or gastrointestinal tract
- Low blood pressure
There is no readily available test, so the only way to confirm a diagnosis is to analyse a blood or tissue sample in one of a small number of specialist laboratories.
Those that live in affected areas are being advised to block holes that may allow rats to enter their homes, disposing of rubbish in covered dustbins, and storing food and water ins sealed containers.
Despite these measures, there is a lack of effective medical tools available to prevent the disease, including a vaccine.
Dr Weller said: “It is likely that a vaccine could be found for Lassa – reducing the possibility of an outbreak becoming a global health emergency – but as with other epidemic diseases that mainly affect poorer countries, progress has stalled.
“Vaccine development is a long, complex and costly process. This is especially true for emerging epidemic diseases, where a prototype vaccine can usually only be tested where there is an outbreak.”