BLOEMFONTEIN – A cruise ship which was docked off Cape Verde at the African coast following confirmation that an outbreak affecting passengers is caused by Andes virus, a rare hantavirus strain typically found in Argentina.
Prof Felicity Burt, principal medical scientist in the pathogen research laboratory within the division of virology at the National Health Laboratory Service and the University of the Free State, said the risk of widespread transmission remains low despite the confirmation.
“Humans are considered dead-end hosts of the virus,” said Burt, who holds a South African research chair in vector-borne and zoonotic pathogens research.
Hantaviruses are carried primarily by rodents and transmitted to humans through aerosols from infected rodent urine, faeces and saliva, and less frequently from rodent bites. The Andes virus has been associated with person-to-person transmission, but this occurrence is rare and has only been documented in a small number of outbreaks.
Limited human-to-human transmission has been recorded on rare occasions, requiring extremely close contact. In each documented instance, spread was facilitated by extremely close contact of individuals living in confined households or attending crowded social events. In all cases, interhuman transmission was limited and spread of the virus contained.
Hantaviruses cause two distinct disease types depending on the strain. New World hantaviruses, such as Sin Nombre virus and Andes virus, are found in North and South America and are associated with hantavirus cardiopulmonary syndrome, an acute respiratory disease. The fatality rate can reach 50%.
Old World hantaviruses, such as Hantaan virus and Puumala virus, are found in Asia and Europe and cause haemorrhagic fever with renal syndrome, with fatality rates ranging from less than 1% to 15%.
The first hantavirus was isolated from rodent tissues in 1981 and named Hantaan virus after the Hantan River, which flows from North to South Korea. The virus was linked to Korean haemorrhagic fever, an illness common among soldiers during the Korean War.
Before 1993, disease caused by hantaviruses had only been confirmed in Asia and Europe. The picture changed after a cluster of previously healthy individuals presented with acute respiratory distress syndrome and a high fatality rate in the Four Corners region of the United States.
A novel hantavirus was confirmed as the cause, marking the first time a hantavirus had caused a respiratory illness with significant fatalities. The naming became controversial, with proposed names including Four Corners virus and Meurto Canyon virus rejected due to concerns about social stigma affecting the region. The virus was finally named Sin Nombre virus, translating to “without a name virus”.
Active surveillance identified additional hantaviruses in multiple locations throughout North and South America, with more than 20 viral species detected. Hosts have expanded beyond rodents to include bats, shrews and fish, but only rodent-borne hantaviruses have been transmitted to humans and caused disease.
Human cases occur more commonly in rural settings where residents have closer contact with rodent populations and are exposed to rodent urine and faeces in homes, fields, forests or rodent-infested buildings. Outbreaks are influenced by ecological and environmental factors that impact rodent populations and activities.
Further epidemiological investigations and genome data will assist with understanding the transmission of the virus among infected individuals in this outbreak.
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