As was with Europe, only those infectious diseases transmitted directly from rodents to humans will be considered below.

The hantaviruses

The distribution of the hantaviruses has been described in the section dealing with this group of infections in Europe. Hantaviruses are a diverse group of RNA arboviruses in the Bunyaviridae family and are parasites of small mammals, predominantly peridomestic and commensal rodents. In most cases human infection is manifested by one of a variety of acute illnesses involving haemorrhagic fever and renal disease. Adult rodents show persistent infection without any clinical manifestations and secrete virus for prolonged periods. Following inoculation, a viraemia develops in the rodent during which the virus is disseminated throughout the body. The virus is found in the lungs, spleen and kidneys for long periods in the rodent, perhaps for life. Saliva appears to play an important role in the horizontal transmission of the virus between rodents.

Man is probably infected through the respiratory route via aerosols of virus particles excreted by rodents in their lungs, saliva, urine and faeces. Transmission has also been documented following bites by rodents. Horizontal transmission among humans has not been documented, although blood and urine are infectious during the first 5 days of illness. It is generally accepted that arthropods are not involved in transmission of the viruses between rodents and from rodents to man. Many hantavirus isolates have been isolated from humans and rodent hosts and are typed according to their serological cross-reactivity. There are at least 14 subtypes.