Warming world, emerging viruses: The new health threats facing NZ

The dull queasiness. The gut cramps. Cold sweat on the forehead, a reeling stagger to the toilet. A “bit of gastro” is a mild euphemism for what can be an efficient but wrenching and potentially dangerous bodily response to unwanted bacteria.

Last September, in the middle of end-of-year exams, more than 150 students at a University of Canterbury hall of residence were floored by Clostridium perfringens bacteria after eating a chicken souvlaki dinner.

In December 2023, more than 60 people in Queenstown came down with cryptosporidiosis (“crypto”), caused by a parasite transmitted in the faeces of infected humans and animals.

In Havelock North in 2016, contaminated drinking water caused an outbreak of campylobacteriosis, leading to thousands of gastroenteritis cases, 42 hospitalisations and four deaths. Several people also ended up with serious long-term neuropathies, when the body’s immune system attacks the nerves, says Nigel French, distinguished professor of infectious disease epidemiology at Massey University and former chief science adviser for Te Niwha, the infectious diseases research platform hosted by the University of Otago and Environmental Science and Research (ESR). “It’s often forgotten that these diseases can be fatal and cause very debilitating illnesses.”

At this fishing, picnicking, BBQ-sizzling time of year, care around food handling, cooking and storing is a no-brainer. According to MPI, about 200,000 New Zealanders get food poisoning every year, the most common causes being campylobacter, salmonella, E coli and yersinia. This figure is likely to be skewed – it includes those infected overseas and ignores those who don’t leave their sick bed to go to a GP clinic or hospital or whose illness falls under the less specific “acute gastro” category.

Climate change, with its volatile tailwind of rising temperatures, increasing humidity, changing rainfall, warmer oceans, drought and extreme weather events, is upping the ante, setting up the right environmental conditions for new and more hardy pests and pathogens around the planet.

Already, increases in land surface temperature globally have been linked to the spread of tick-borne illnesses such as Lyme disease across much of Canada and encephalitis in northern Europe.

Warmer, wetter climates are driving mosquito-borne infections such as zika, malaria and chikungunya virus into higher altitudes. Small outbreaks of dengue have been recorded in Texas and southern France.

Otago University environmental epidemiologist Simon Hales says this is partly because the world is “possibly a degree warmer than [it] used to be. It doesn’t sound a lot, but it is if you are a mosquito.”