A major study into a potentially fatal virus that can cause uncontrolled bleeding from the mouth, nose or vagina has pinned the blame on disease-carrying rats.
Experts have been looking at the reason for an “unusual ” spike in Lassa fever cases in Nigeria, which saw more than 140 people die at the start of this year.
Lassa fever is an acute viral hemorrhagic illness which can cause a headache, chest pain, vomiting and diarrhea.
More severe symptoms, occurring in 15-20 percent of patients in Nigeria, “include facial swelling, uncontrolled bleeding from the mouth, nose, vagina and gastrointestinal tract”, says the International Association for Medical Assistance to Travellers.
Between January 1 and April 15 this year, 1,849 suspected cases were reported from 21 states across Nigeria.
Lassa fever killed 142 people in Nigeria during that period, said the Nigeria Centre for Disease Control (NCDC).
The virus is spread through contact with food or household items contaminated with rats' urine or feces or after coming into direct contact with the bodily fluids of an infected person.
There is currently no approved vaccine to prevent Lassa, which belongs to the same family as Marburg and Ebola.
In April, the World Health Organization (WHO), which regards Lassa as a “threat to global health”, declared that Nigeria was suffering from an outbreak and a public health emergency.
By May 27, the NCDC had reported 431 laboratory-confirmed cases in patients, including 37 health care workers, with an estimated fatality rate of 25 percent.
Health bosses were concerned about the rising cases, and asked experts whether it was due to greater human-to-human transmission – for example, that Lassa had mutated into a super-bug that was spreading across Nigeria's population, reports Nature.
However, experts have now determined that is not the case.
Their findings, outlined this week in The New England Journal of Medicine, blamed the spike in rat fever cases on “ongoing cross-species transmission from local rodent populations”.
The report says that Lassa fever is a viral hemorrhagic illness that is “endemic to parts of West Africa and causes more than 300,000 illness and 3,000 deaths each year.
“We found no evidence that a particular viral strain or extensive human-to-human transmission drove the increase.”
Experts said while they have no clue as to why there has been an “unusual increase in Lassa fever cases” the spike may be linked to a rise in the number of rats carrying the virus.
It's hoped that the findings will help researchers develop vaccines against the illness.
People can be prevented from contracting the virus by being vigilant with their personal hygiene and avoiding all contact with rats.