The reservoir of infection is a particular type of rat—the Natal multimammate mouse which is found in sub-Saharan Africa. It is normally resident in the bush but is driven into houses during bush burning during the dry season. The virus lives and multiplies in the rat. It is contained in the urine and stool of rats.
The infection gets into human population when the urine and/or faeces of an infected rat contaminate exposed food and man contracts the disease if he eats the contaminated food. The faeces of the infected rat can become dried up and with dust can be breathed in by man during sweeping of the floor or in a windy situation.
Within the human population, Lassa fever infection spreads through the body fluids of victims which contain the virus; the body fluids include saliva, sweat, nasal discharge, blood, tears, urine and vomit.
On contact with such fluids, the virus enters the body through broken skin (injuries on the skin) and the mucous membrane covering the-eyes, mouth and nostrils- all these areas are covered by thin skin called mucous membrane. The hand can carry the virus to any or all of these places.
Lassa fever can also spread by contact with objects contaminated by the virus; these include clothing/handkerchiefs/beddings of infected persons and any other items contaminated by fluids from infected persons.
From the above, you can see that certain categories of persons are most at risk of contracting the disease.
1. Healthcare Providers
Healthcare providers are most at risk; these include doctors, nurses, laboratory scientists, virologists, ward attendants, hospital laundrymen/women. Even among these people, nurses and doctors are most at risk. In an outbreak in Ebonyi State a few years back, some healthcare workers lost their lives in combating the outbreak. In the current outbreak in Lagos State, a doctor was infected in LUTH.
Caution must be exercised in caring for the victims; Use of face masks, gloves, gowns, goggles etc when attending to infected persons is mandatory for all health workers; they are at great risk.
2. Mortuary workers 
One other group that is at great risk is that of mortuary workers, they have to prepare the dead for preservation or for burial. The situation is worse if they were unaware of the cause of death as being due to Lassa fever
Hence the cause of death must be established before any action is taken by the mortuary.
3. Families of infected persons, healthcare providers, mortuary workers
Family members of Lassa fever like healthcare providers, mortuary workers and farmers are at great risk of contracting Lassa fever. If they (healthcare providers) are not aware of the patient’s actual disease or were not cautious enough in managing the patient, they could carry the virus in their clothing or other materials.
Anyone with persistent fever, headache, vomiting, sore throat and occasional hearing loss should be taken to hospital.
Anyone who comes in contact with such a person must wash his hands thoroughly with soap and water.
4. Farmers
The reservoir of infection is a bush rat and hence can easily contaminate the exposed food of farmers.
Farmers are at high risk of Lassa fever infection.
5. Rural dwellers
Rural dwellers are also at great risk of Lassa fever, during bush burning in dry season, the bush rats run into the homes in the rural areas which are usually dirty or farm houses which are also dirty.
In the rural areas, the knowledge of food hygiene is rudimentary or non-existent ; consequently infected rats can easily contaminate food including garri for soaking.
6. Residents of areas without water.
The easiest way of breaking the transmission chain of Lassa virus in human population is by the regular washing of hands with water and soap. Consequently, where there is no water, hand hygiene could be compromised, thus encouraging the spread of Lassa fever. The infection is restricted for now to West Africa.
7. Residents of Crowded and Dirty homes.
Crowded and dirty homes could encourage the spread of Lassa if an unknown infected case is in the home. Clean homes rarely harbour rats, the reservoir of the infection.
If the home is clean there will be no rats and if a home is not crowded, the contact between persons is reduced and hence reduced transmission.

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