Lassa virus - Krobs



The Lassa virus is one of the many viruses that can cause hemorrhagic1 fever. It was isolated for the first time in 1969 in Lassa, Nigeria and is mainly found in several regions in West Africa where it is endemic1.


Transmitted by a rodent

The natural host for Lassa virus is the african natal multimammate mouse (Mastomys natalensis), also called African rat, and closely associates with humans. The virus spreads from rat to humans through food contaminated with rat urine and poop. Unlike the Ebola virus, another virus responsible for hemorrhagic fever, human-to-human transmission is rare for the Lassa virus.


A disease with different degrees of severity

The Lassa virus goes unnoticed in 80% of the infected people, causing no symptoms. For the other remaining 20% the virus can be extremely dangerous and cause a devastating hemorrhagic fever. The disease starts after 6 to 21 days of incubation, with symptoms similar to those of other tropical diseases such as malaria. Strong fever, headaches, vomiting and muscular pain can be observed. Sometimes, the disease gets worse by causing bleeding of the mouth, nose, and stomach, which can lead to coma and death.

The Lassa fever is extremely dangerous for pregnant women, especially towards the end of their pregnancy. The mortality rate is of over 80% for pregnant women and 100% for the unborn child.

We are looking for a vaccine

Sadly, there are no effective treatments for this disease. We can only try to alleviate the symptoms of the patients. Since it is caused by a virus antibiotics3 are ineffective.

To this day, no vaccines protect against the Lassa fever, but promising research is ongoing. Prevention relies on a good hygiene and measures to prevent rodents from entering the house.

Hemorrhagic1 = Associated with an important bleeding caused by the rupture of a blood vessel.

Endemic2 = Defines a disease which is present in a defined geographic area.

Antibiotic3 = = A drug which allows to kill bacteria or at least to stop their growth. Antibiotics act against bacteria, but do not help treat diseases caused by viruses and parasites.