The Lassa virus causes Lassa fever which is one of the viral hemorrhagic fevers.
The animal that serves as a reservoir for the Lassa virus is a rodent that is commonly called the “multimammate” rat. It belongs to the genus and species Mastomys natalensis. When the multimammate rat is infected, it does not fall ill but it carries the virus and sheds it in its urine and faeces for a long period of time or even for the rest of its life. These rats reproduce often. And they produce many offspring. They are very many in Central, East and West Africa.
There are different ways through which the virus spreads or is transmitted:
- The Lassa virus is transmitted to humans when they are exposed to the faeces or urine of a particular kind of rat called the “multimammate” rat.
- It can also be transmitted/spread from person to person when an individual comes in contact with urine, blood, faeces and other secretions from the body of an infected person. This can occur in the society or in hospitals (for instance, when needles used on an infected person are re-used on an uninfected person).
- It has also been reported that the Lassa virus can also be spread sexually.
- The virus can be transmitted to humans when it comes in contact with open cuts and sores on the skin.
- It can also be spread when particles of contaminated rodent excreta in the air are inhaled – which could be due to sweeping, etc.
- The Lassa virus can be swallowed in contaminated food and utensils.
- The Lassa virus can also be spread through semen for up to three months after infection – which means even after the patient has recovered and no longer has other symptoms of the disease.
It is not certain when exactly human beings become infectious after they are infected and for how long they are infectious. However, it has been found that the virus reaches its highest levels in the blood about four to nine days after the onset of symptoms.