Glossary · Ecology
Rodent reservoirs
Wild rodent species that chronically carry a hantavirus without apparent symptoms. The Andes virus reservoir is the rodent Oligoryzomys longicaudatus (colilargo) in Patagonia.
Rodent reservoirs are the wild rodent species that naturally host hantaviruses. In these animals, infection is chronic and asymptomatic: the virus replicates without causing disease but is continuously shed in urine, faeces and saliva. Human contact with these excretions is the main route of contamination. For Andes virus, the reservoir is the colilargo (Oligoryzomys longicaudatus) of Patagonia.
The notion of animal reservoir #
Definition #
In epidemiology, a reservoir is a host species in which an infectious agent persists durably and which serves as the source of transmission to other species, in particular humans. For hantaviruses, the reservoirs are almost exclusively wild rodents, with a strict association rule: each viral strain has its specific reservoir, the product of long co-evolution.
Diversity #
The WHO and the scientific community count more than 80 host species of hantaviruses worldwide: 51 rodent species (the main ones), 7 bat species and 20 shrew-like species (shrews, moles). This diversity explains why new hantaviruses continue to be identified regularly as surveillance of wild animal populations expands.
The colilargo, reservoir of Andes virus #
Description #
Oligoryzomys longicaudatus, the colilargo ("long tail"), is a small sigmodontine rodent endemic to the southern Andes range. Its distribution extends from southern Peru down to Tierra del Fuego, across Chile and Argentina. It colonises diverse habitats: humid temperate forests, Patagonian steppes, edges of agricultural and peri-domestic areas.
Population cycles #
The colilargo's population density varies sharply, mainly with the cyclical proliferation of the bamboo Chusquea (species valdiviensis, culeou, etc.). This Andean bamboo flowers massively and synchronously every 60 to 70 years, producing huge quantities of seeds that constitute a major food resource for rodents. The mass proliferation that follows ("ratada" in Spanish) can multiply densities a hundredfold and historically coincides with peaks of human hantavirus pulmonary syndrome cases.
Notable cases #
In 1990, more than one million hectares of Chusquea valdiviensis flowered simultaneously in Chile, triggering a population explosion of the colilargo and the appearance of human cases. It is in this context that Andes virus was identified for the first time a few years later. The Epuyén outbreak in 2018-2019 (Argentina) was preceded by a local increase in rodent densities.
Reservoirs of the main other hantaviruses #
| Strain | Reservoir | Location |
|---|---|---|
| Andes (ANDV) | Oligoryzomys longicaudatus (colilargo) | Argentine and Chilean Patagonia |
| Sin Nombre | Peromyscus maniculatus (deer mouse) | North America (western United States) |
| Hantaan | Apodemus agrarius (striped field mouse) | East Asia |
| Seoul | Rattus norvegicus (brown rat) | Global (urban areas) |
| Puumala | Myodes glareolus (bank vole) | Northern Europe |
| Dobrava | Apodemus flavicollis (yellow-necked mouse) | Balkans |
Consequences for surveillance and prevention #
One Health #
The One Health approach promoted by the WHO, FAO and WOAH integrates surveillance of rodent reservoir populations as a pillar of human hantavirus prevention. Monitored indicators include: density of sentinel populations, viral seroprevalence in trapped rodents, climatic and ecological conditions favourable to proliferation peaks, and predictive modelling of seasonal risk.
For the general public #
Limiting exposure to wild rodents is the main preventive measure: building tightness (sealing holes), airtight food storage, careful cleaning of spaces where rodents may have entered (cellar, attic, outbuilding), with prior spraying of diluted bleach and use of an FFP2/N95 mask. The common domestic rodents of European cities (mice, brown rats) do not carry Andes virus, but the brown rat can carry Seoul virus.
For travellers #
Travellers in endemic areas (notably Argentine and Chilean Patagonia) are advised to avoid rustic accommodation that has been closed for a long time and may be colonised by rodents, and to favour ventilated and recently cleaned accommodation. This is the likely route of contamination for the first MV Hondius patients, who were probably infected before boarding during stays in South America.
Key figures
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51
Number of rodent species identified as hantavirus reservoirs worldwide, out of more than 80 host species in total (including bats and shrew-like mammals).
PLOS Pathogens — A human pathogenic hantavirus circulates in diverse rodent reservoirs
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1 reservoir = 1 strain
General rule: each hantavirus strain is strictly associated with one rodent reservoir species, the result of long co-evolution.
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1 million ha
Area of Chusquea valdiviensis bamboo that flowered simultaneously in 1990 in Chile, triggering a population explosion of colilargo and a peak of hantavirus cases.
Wikipedia — Oligoryzomys longicaudatus (referenced synthesis)
Standards & references
- WHO — One Health — Integrated approach to human, animal and environmental health, which includes surveillance of rodent reservoir populations.
Frequently asked questions
Do all rodents carry hantavirus?
No. Only certain wild rodent species are hantavirus reservoirs, and each viral strain is usually associated with a single host species. Common domestic rodents (the house mouse Mus musculus, the brown rat Rattus norvegicus in urban areas) do not carry Andes virus. The brown rat can, however, transmit Seoul virus (responsible for HFRS) on a global scale.
Which rodent carries Andes virus?
The main reservoir of Andes virus is the rodent Oligoryzomys longicaudatus, commonly called the colilargo ("long tail" in Spanish). It is a small sigmodontine rodent endemic to the southern Andes range, from southern Peru down to Tierra del Fuego. Its population density varies sharply with the cyclical proliferation of Chusquea bamboo.
Why are reservoir rodents not sick?
Infection in the rodent host is chronic and asymptomatic: the result of long co-evolution over several million years between the virus and its reservoir. The rodent's immune system tolerates the virus without clearing it, and the virus replicates silently in several organs. The animal sheds virus throughout its life in urine, faeces and saliva, without ever showing symptoms.
Does climate change affect the risk?
Yes, indirectly. Studies in Argentine Patagonia show that the spatial distribution of the colilargo is sensitive to climate change scenarios. Changes in rainfall (El Niño effect) and the cyclical proliferation of bamboo influence rodent densities and therefore human risk. The mass proliferation ("ratada") that followed bamboo flowering in Chile in 1990 coincided with a peak of human cases.
Further reading
- Oligoryzomys longicaudatus — Wikipedia — Wikipedia EN (synthesis)
- Hantavirus reservoir distribution sensitivity to climate change in Argentine Patagonia — International Journal of Health Geographics (scientific publication)
- PLOS Pathogens — Diverse rodent reservoirs — PLOS (scientific publication)