Lassa virus is spread from rodents to humans, but some of the exact mechanisms of transmission are unclear. The virus is excreted by rodents in their urine, faeces, and blood and may also be present in saliva. There is some evidence that the virus can spread through the inhalation of the aerosolised virus. It is assumed that the virus is spread to humans through contact with food or surfaces (such as dirty pots and pans) that have been contaminated. Other means of infection include during the preparation of rodents for food (when people often get blood and urine from rodents on their hands), and bites. Prolonged exposure to rodents carrying the virus, such as living in a household that is infested with Lassa positive rodents, increases the risk of infection. Human to human transmission is estimated to account for 20% of reported Lassa cases and also occurs through exposure to infected fluids. This usually occurs when caring for people at home or in community settings, or through inadequate use of barrier nursing techniques within treatment facilities. Transmission can also occur through the use of contaminated medical equipment such as reusing needles.
Policy-relevant findings
- As there are likely to be a number of different routes of infection, intervention strategies must become more context-specific in each instance
- A more holistic approach to rodent control is needed, utilising effective specific control methods but alongside changes to environmental and domestic hygiene and building materials
- Further training in barrier nursing techniques and increased medical equipment to facilitate this are needed to reduce secondary human-human transmission within healthcare facilities
