Summer surge: warming weather in Nepal sees rise in deadly diarrhoea
Is climate change driving a spike in life-threatening Shigella infections in mountainous Nepal?
- 3 May 2023
- 5 min read
- by Chhatra Karki
Dr Samikshya Malla, medical officer at Jajarkot District Hospital in mountainous western Nepal, is bracing for the summer spike in diarrhoea cases. Between May and July, she says, she expects as many as 10 diarrhoea patients a day, with more than 50% of the hospital's diarrhoea patients being children below the age of five.
"The hospital's 20 beds are often exceeded by the number of diarrhoea patients seeking treatment during the summer," Dr Malla says, explaining that poor hygiene practices, like not washing hands well after using the toilet, drive the spread of the various microbes responsible for diarrhoeal disease.
A higher rate of extreme weather events like floods, cyclones and hurricanes amid the global climate crisis are generally liable to exacerbate contamination of drinking water by diarrhoea-causing pathogens.
But she also believes there is another factor driving the summer bump: the abnormally high temperatures hitting the remote Himalayan villages of the district in recent years.
That tallies with the observations of Meghnath Dhimal, Chief of the Research Section at Nepal's National Health Research Council (NHRC).
Credit: Chhatra Karki
In a recent Lancet Global Healthpaper, he and co-author Dinesh Bhandari zero in on the bacterium Shigella, which has been reported to be the most common cause of childhood diarrhoea in low and middle income countries, pointing to evidence that shigellosis becomes more likely at higher temperatures.
Such patterns have been observed in epidemiological studies from South Korea and China, they write, adding that "laboratory-based findings have suggested that virulence genes responsible for coding Shigella toxins and genes responsible for host-cell invation are highly expressed at 37°C, increasing pathogenicity."
A higher rate of extreme weather events like floods, cyclones and hurricanes amid the global climate crisis are generally liable to exacerbate contamination of drinking water by diarrhoea-causing pathogens.
Overall, diarrhoeal disease incidence in Nepal increased some 4.4% with a 1°C increase in mean temperature and a 1cm rainfall increase, Dhimal and co-authors found in 2022 study published in the International Journal of Environmental Research and Public Health.
As Dhimal told VaccinesWork, "Climate change, leading to an overall rise in temperature and alternation in weather patterns, is contributing to the burden of diarrhoea in the mountainous regions of Nepal."
Although Jajarkot District Hospital has laboratory facilities, Dr Malla explains that systematic data on the specific bacterium, virus or protozoan causing each case of diarrhoea is not kept. What is known is that the hospital currently expects around 1,000 diarrhoea patients annually, and that that number is trending upward.
Credit: Chhatra Karki
Over the past four decades, the Department of Hydrology and Meteorology (DoHM) has reported a 2.5°C increase in Nepal's maximum recorded temperature. The country's average annual maximum temperature has risen by 0.056°C, with higher elevations experiencing a higher rate of warming.
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Dr Sudeep Thakuri, a climate scientist and the Dean of the Faculty of Environment and Engineering at Nepal's Mid-West University, explains that certain microbial organisms have the ability to thrive at higher temperatures, seeing increased reproductive rates in warmer climates. That's part of why remote villages with inadequate sanitation facilities, such as those located in Jajarkot, are at rising risk of shigellosis as temperatures climb.
"The term 'climate change' refers to a general increase in temperature and changes in weather patterns. Our findings suggest that higher altitudes are experiencing temperature increases – creating a favourable environment for microbial organisms to thrive and spread diseases such as diarrhoea through faeces-contaminated food and water," Dr Thakuri says.
Prof Dr Jeevan Bahadur Sherchand, Senior Consultant to WHO and former Research Director at Tribhuvan University's Institute of Medicine, explains that Shigella bacteria multiply rapidly, allowing disease outbreaks to spread fast. "Climate change is expected to increase the activity of Shigella bacteria, particularly in food, as temperatures rise," he confirms, noting that 25% of diarrhoea cases in Nepal are currently estimated to be caused by Shigella.
Credit: Chhatra Karki
But behavioural and infrastructural shifts can do a lot to protect vulnerable communities from the anticipated threat. "Poor sanitation – including unsanitary living conditions, poor hand hygiene, eating unwashed fruit – are contributing factors to the spread of the disease. Poverty stricken rural areas like Karnalia and Sudu Paschim, and slum areas in Kathmandu are particularly at risk," Prof Dr Sherchand warns.
And the risk is serious. Sita KC, a resident of Khalanga in Jajarkot, recently took her ill four-year-old son to Jajarkot Hospital, where he was diagnosed with shigellosis. She says he'd been suffering with watery, bloody diarrhoea, and severe stomach pain. The boy recovered – but many children don't.
Dambar Bikram Karki, Assistant Health Worker at Barekot Basic Health Service Center in Jajarkot, says an outbreak of infectious diarrhoea claimed 375 lives here in 2009.
According to WHO, diarrhoea causes more than 2.2 million deaths of children under five years old annually worldwide, while in Nepal, diarrhoea causes 6,071 deaths per year.
"Coordination among all relevant ministries is crucial for effective management and prevention of diarrhoea outbreaks," says Dr Chuman Lal Das, Chief of Ministry of Health and Population, Epidemiology and Disease Control Division (EDCD). "Climate change has been identified as a risk factor for diarrhoea, and efforts should be made to mitigate its effects."
The Ministry of Health is creating a national health adaptation plan addressing vector-borne diseases, water scarcity, and Shigellosis. "Early warning and prompt treatment can prevent epidemics, and health promotion is necessary to prevent the spread of communicable and non-communicable diseases," Dr Das says.
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