Can global warming trigger cholera outbreaks?

For quite some time, scientists have been examining the health consequences of climate change with the advent of changing weather patterns that are reportedly triggering sweltering heat waves throughout human habitats and causing sea temperature to rise.

Published in Nature Disease Primer, a recent review co-authored by icddr,b researchers suggests that rising sea temperature caused by climate change may be favouring the incidence of different vibrio-related diseases.

Rising sea level means seawater getting closer to human habitats. Photo: GMB Akash / icddr,b

These can include, severe diarrhoeal disease, cholera caused by Vibrio cholerae from marine, estuarine or even freshwater sources and invasive illness caused by some virulent Vibrio species as well as wound infections and gastroenteritis caused by other types of Vibrio species.

The review was authored in collaboration with researchers from the Centre for Environment, Fisheries and Aquaculture Science (CEFAS), University of North Carolina, Duke University Marine Laboratory, University of Florida and Harvard Medical School, USA.

Vibriosis, a deadly systemic infection, may develop through eating raw or undercooked seafood such as oysters and shellfish containing the vibrio pathogens, or when sea water carrying virulent vibrio species comes in contact with skin wounds, notes US Center for Disease Control and Prevention (CDC).

The notorious pathogen Vibrio cholerae belongs to the cholera-causing Vibrio genus (type), which includes other non-cholera-causing vibrio species responsible for foodborne illness and wound infection. These non-cholera-causing pathogens pose threat to parts of the world where raw seafood is eaten more commonly.

Microscopic view of cholera-causing Vibrio cholerae. Photo: Phil Moyer. CC BY-NC-ND 2.0


Will cholera vaccines work anymore?

“Oral cholera vaccines are effective public health tools for controlling cholera,” says Dr Firdausi Qadri, an senior emeritus scientist at the infectious diseases division at icddr,b and a co-author of the review. The disease can be prevented by improvements in water, sanitation and hygiene (WASH), coupled with community awareness improvements in cholera- endemic countries, she observed.

Although there are effective ways to control cholera, warming of coastal habitats caused by climate change may expand the effects of all vibrio species, suggests the new Nature review by referring to most recent evidence. Claims as such are backed by findings, noting associations between abundance of these bacteria and environmental warming, and evidence of increasing wound infections in higher temperature areas.

Rising sea-level will engulf more land. Photo: Mohammad Tauheed. CC BY-NC 2.0

“All vibrio species originate from seawater. They tend to thrive well and initiate disease outbreaks in endemic regions when water gets warmer,” says Dr Munirul Alam, senior scientist and a microbiologist with icddr,b infectious diseases division and a co-author of the review.

Also, rising sea-level due to global warming means seawater engulfing more land and getting closer to human habitats. “Consequently, increased human exposure to seawater carrying these salt-loving pathogens may result in more frequent and bigger disease outbreaks,” he explains.

Evidences of rising infections associated with sea-level rise and warmer climate areas suggest that climate change induced warming sea temperature may be facilitating the growth and multiplication of these pathogens, underscores the review.

Such warnings have driven scientists to look for methods to combine remote- sensing-based approaches with epidemiological and regional climate change models, notes the review. These would help them determine the extent of risks related to global warming and sea-level rise affecting the coastal regions to be able to mobilise logistics to combat future outbreaks.

Muhamamd Zahir Hassan Nabil