Over half of human diseases made worse by climate hazards
Climatic hazards bring pathogens closer to people.
What you need to know:
- The study shows that global warming precipitation and floods, drought, storms, natural cover change, ocean climate change, fires, heatwaves and change in sea level aggravated diseases by worsening transmission of viruses, bacteria and other pathogens.
- The pathogens were transmitted through water, parasites, direct contact and food
Climate hazards resulting from greenhouse emissions have heightened severity of 218 of 375 infectious diseases known to affect human beings worldwide.
A study conducted by researchers at the University of Hawaii in Honolulu sought to find case examples of pathogenic diseases affected by climate hazards such as floods, droughts and rise of sea level.
The study shows that global warming precipitation and floods, drought, storms, natural cover change, ocean climate change, fires, heatwaves and change in sea level aggravated diseases by worsening transmission of viruses, bacteria and other pathogens. The pathogens were transmitted through water, parasites, direct contact and food.
“While numerous biological, ecological, environmental and social factors contribute to the successful emergence of a human pathogenic disease, at the most basic level, it depends on a pathogen and a person coming into contact, and the extent to which peoples’ resistance is diminished, or the pathogen is strengthened by a climatic hazard,” it adds.
Based on this, the study further explains that climatic hazards bring pathogens closer to people, with warming associated with range expansion of parasites such as mosquitoes, viruses and bacteria. Warming also allows pathogens to survive winter, which encourages outbreaks of other viruses.
Drought and heavy precipitation, noted the researchers, cause movement of livestock to suitable areas, which exposes them to pathogens and outbreaks of diseases such as anthrax and haemorrhagic fever. Humans, on the other hand, are affected by changes in precipitation and temperature, which impacts human social gatherings, and the transmissibility of viruses such as influenza and Covid-19.
“Heavy rainfall could exogenously induce social isolation, helping to explain lower Covid-19 cases after heavy rainfall. However, increased cases of Covid-19 were associated with increases in precipitation in Indonesia, perhaps reflecting different behavioural responses to extreme rain,” said the study.
The study also associated higher temperatures with increased cases of Covid-19, saying that extreme heat may forces people indoors, and thus increase the risk of transmission, especially in cases where there is poor or reduced ventilation. Lower temperatures also produce the same results, as people gather together in common spaces.
Warming, drought, heatwaves, wildfires, storms, floods and land cover change led to habitat disruptions, which caused wildlife to move in search of food, and to find new habitats. The study states that Nipah virus and Ebola were associated with bats, rodents and primates moving over larger areas foraging for limited food resources caused by drought or finding new habitats following wildfires.
The study also states that climate hazards have enhanced specific aspects of pathogens, allowing them to adapt to climate change and reproduce. And while their life cycles have accelerated, their incubation periods have shortened, as the severity of the disease has gone up. “Warming had positive effects on mosquito population development, survival, biting rates and viral replication, increasing the transmission efficiency of West Nile virus. Ocean warming and heavy precipitation, which reduces coastal water salinity, appear to provide fertile conditions for Vibrio vulnificus and Vibrio cholerae, this being a leading explanation for Vibriosis outbreaks in areas where this disease is rare," says the study.
