From Watts Up With That?

Essay by Eric Worrall

Just one problem – Ushuaia, the source of the MV Hondius cruise ship outbreak, has a comparable climate to Prince Rupert in British Columbia.

How climate change could help hantavirus find more hosts

Experts say extreme weather is boosting the odds that the pathogens carried by rodents will spill over into human populations.

The cruise ship departed Ushuaia, Argentina, in April with plans to ferry 147 passengers and crew members to some of the most remote places on earth, including Antarctica. But the ship, named the MV Hondius, had its voyage cut short by a rare virus that has killed three and infected several others. 

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The emergency also points to another growing challenge for global public health: Climate change is altering the rainfall, vegetation, and habitat conditions that influence rodent populations — changes that experts say boost the odds that the pathogens these animals carry will spill over into human populations.

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Prolonged drought sends rats and mice into populated areas in search of food, which can put people at higher risk of contracting the virus. Sudden rainfall following drought causes trees and shrubs to produce a windfall of nuts and seeds, which tend to benefit rodents and boost their numbers — all the while increasing the risk of transmission from animal to human.

…Read more: https://grist.org/health/how-climate-change-could-help-hantavirus-find-more-hosts/

My question – Australia has frequent weather extremes and rodent plagues. So why aren’t we overrun with Hantavirus? Hantavirus antibodies have been detected in Aussie rodents, but significant Hantavirus infection isn’t a thing in Australia.

From the Aussie CSIRO;

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Do we have hantaviruses in Australia? 

Australia is unique in the global hantavirus picture. It is the only inhabited continent where no confirmed human cases of hantavirus infection have been recorded. 

However, antibodies to hantavirus have been detected in some Australian rodents, suggesting related viruses are likely present at low levels.  

Several explanations for why there hasn’t been any reported cases have been proposed. One possibility is the lack of diagnosis: perhaps Australian hantavirus only causes a mild, feverish illness with kidney involvement that could easily be attributed to other causes. 

However, anyone who is unwell with persistent or serious symptoms such as respiratory issues should consult their GP for advice. This is especially the case for travellers returning from parts of Europe, Asia or the Americas.  

…Read more: https://www.csiro.au/en/news/All/Articles/2026/May/Hantavirus-explainer

Maybe a few mild human cases slipped through the net, but my point is given the low prevalence of Hantavirus in Australian rodent populations, despite our extreme cycles of drought and flooding rain, and a much warmer climate than Ushuaia in Argentina, it seems reasonable to conclude a warmer climate and greater climate extremes do not cause more Hantavirus cases. It also seems likely something about our warm climate is killing the Hantavirus which is already present in Aussie rodent populations before it becomes a significant problem.

Maybe the virus just can’t stand warm conditions. A lot of viruses can’t.

Who knows, if we get a bit more global warming, maybe cold climate places like Ushuaia will also benefit from less Hantavirus, just like warm climate Australia.

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Andes virus (ANDV) is a hantavirus primarily found in South America (especially Argentina and Chile) that causes Hantavirus Pulmonary Syndrome (HPS), also known as hantavirus cardiopulmonary syndrome (HCPS). It is notable as the only hantavirus with documented (though limited) person-to-person transmission.

Transmission

Primary route: Inhalation of aerosolized virus from the urine, droppings, or saliva of infected rodents (e.g., the long-tailed pygmy rice rat). It can also occur via direct contact with rodents or contaminated surfaces, then touching the mouth, nose, or eyes.

Person-to-person: Possible but uncommon and requires prolonged close contact (e.g., household members, intimate partners, or shared enclosed spaces) and exposure to body fluids. This sets Andes virus apart from other hantaviruses, which do not spread between people. Transmission is most likely early in illness when the person is symptomatic. It is not airborne like COVID-19 or measles.

No evidence of spread via casual contact, food (except possibly contaminated), or vectors like insects.

Incubation period: Typically, 4–42 days (up to 6 weeks) after exposure.

The case fatality rate for Andes virus HPS is high, often estimated at ~35–50% (around 38% in some reports), though early supportive care in well-resourced settings can improve outcomes. Older adults and those with comorbidities face higher risk.