Leishmaniasis is caused by protozoan parasites belonging to the genus Leishmania. The parasites are transmitted by the bite of a tiny – only 2 to 3 mm long – insect vector called the phlebotomine sandfly. There are some 500 known phlebotomine species, but only about 30 have been found to transmit leishmaniasis. Only the female sandfly transmits the parasites.

Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arenavirus family of viruses. Humans usually become infected through aerosol or direct contact with excreta of infected rodents. 

Lassa fever can also be spread between humans through direct contact with the blood, pharyngeal secretions, urine, faeces or other body secretions of an infected person. Person-to-person transmission of Lassa fever has occurred in health care settings after exposure to blood and secretions of infected patients.