In mid-February, parts of India witnessed a second spurt this year in cases of Guillane-Barré syndrome, a nerve condition causing nerve pain and sometimes paralysis, along with difficulties in breathing and swallowing. This outbreak was first reported at the end of January in Maharashtra and later in Andhra Pradesh in February and is suspected to be caused by a stomach bug.
Maharashtra has reported over 211 cases and 11 deaths as of February 19, according to news reports. Meanwhile, media has also reported 17 cases and two deaths from Andhra Pradesh since mid-February.
The World Health Organization says that while the exact cause of Guillane-Barré syndrome, or GBS, is not known, most cases follow a viral or bacterial infection. One of the most common risk factors is infection with the bacteria Campylobacter jejuni, which causes gastroenteritis. The immune systems go into an over-drive, attacking the body’s peripheral nerves.
In the current outbreak too, Campylobacter jejuni, is suspected to be the most likely cause, says Siara Rao Ajjampur, professor of microbiology at the Christian Medical College, Vellore.
Climate and food bugs
Seasonal spikes in GBS cases have been known to occur, with an increase in the number of cases during winter, according to Monojit Debnath, professor of genetics at the National Institute for Mental Health and Neuroscience, Bengaluru, who has been studying nerve disorders and particularly GBS.
GBS is a post-infection aberration in the immune system. Its spike in winter is likely linked to respiratory tract infections and flu cases that also rise in winter. Debnath cites the examples of previous outbreaks in French Polynesia and Latin America from 2013 to 2016, which was linked to a Zika virus epidemic; and a more recent 2019 outbreak in Peru which was linked to a C jejuni outbreak.
Scientists worldwide have been exploring whether environmental changes triggered by global warming, especially extreme temperatures and floods can result in increased spread of, among others, food-borne microbes such as Campylobacter sp, Salmonella, and Escherichia coli.
Data from India have contributed to larger meta-analysis that have looked at climate change and Campylobacter, the bacteria linked with the current GBS outbreak, and a link with increasing global temperatures, says Ajjampur. “This is multi factorial due to bacterial survival strategies and increase in transmission due to changes in human behaviour associated with increase in temperature including water and food scarcity.”
Although difficult to culture in most laboratories, which is also why they are under-reported, most species of Campylobacter employ a number of strategies to survive in harsh environments, especially water, she says. These include activating biochemical pathways, and forming “biofilms” in which Campylobacter species gather together with bacteria and microbes and encase themselves with a protective barrier that helps them endure harsh environments. “Data suggest they can survive in well-water for long periods of time especially in colder temperatures,” says Ajjampur.
A December 2024 report in One Health on climate change and food-borne pathogens, which includes Campylobacter sp concludes that “most of the available literature points towards a rise in climate-associated food-borne pathogen associated outbreaks across the globe due to the varying responses of different groups and in their transmission patterns to ambient temperature”.
“The ongoing effects of climate change have exacerbated two significant challenges to global populations: the transmission of food-borne pathogens and antimicrobial resistance through the food chain,” the report says. It was based on a review that used the latest available scientific information to explore how climate-related factors such as rainfall, floods, storms, hurricanes, cyclones, dust, temperature and humidity impact the spread of the food-borne pathogens Salmonella, E. coli, Campylobacter, Vibrio, Listeria, and Staphylococcus aureus.
The authors also explored the complex dynamics between environmental changes and the heightened risk of food-borne diseases, analysing the contribution of wildlife, insects and contaminated environments in the proliferation of anti-microbial resistance (AMR) and climate change.
Approximately 30% of all human infections with Campylobacter are attributed to poultry consumption, 20%-30% from beef and a smaller percentage of infections arise due to pathogenic strains from other sources, including game animals, the report says. While Campylobacter levels in chicken flocks fluctuate with temperature and humidity, in the case of human infections, the cases are linked to fluctuations in temperature and precipitation, particularly during extreme precipitation events, it says.
The report cites, among others, a study in Ontario in Canada that showed “a positive correlation between climate and bacterial prevalence”. A second report in 2024, from The Lancet Discovery series says that “for each 1 °C rise in temperature, the risk of non-typhoidal Salmonella and Campylobacter infections increased by 5%. There have been similar reports in the past 10 years.
A report of the European Climate and Health Observatory, published in August 2023, says that “a warmer and wetter climate with more extreme events will facilitate bacteria multiplication and people’s exposure to pathogens. A 2021 report in Lancet Regional Health points out that many of the pathogens that cause food-borne diseases “are able to persist in the environment, can sustain heat stress, and are infective at a low dose.” Of these, Campylobacter, which is the most common bacterial cause of diarrhoeal disease in developed countries, shows “a strong association with seasonality and climate variability, mainly with increased temperatures that may increase bacterial contamination at various points along the food chain.”
“Since Campylobacter cannot replicate outside of the host, hot ambient conditions may actually influence people’s behaviour, rather than replication rates which, in turn, may be translated into riskier patterns of food consumption.
Researchers from Denmark, Finland, Norway and Sweden reported in Scientific Reports in 2020 that their study’s results show that “climate changes alone can result in an average 145 excess annual cases of Campylobacter by 2040-2049 and almost 1,500 by the end of the 2080s in each country per year”. “Global climate change is predicted to alter precipitation and temperature patterns across the world, affecting a range of infectious diseases and particularly food-borne infections such as Campylobacter,” the report says.
This study used national surveillance data to analyse the relationship between climate and the bacterial infection campylobacteriosis in the four Scandinavian countries and estimate the impact of climate changes on future disease patterns. “We show that Campylobacter incidences are linked to increases in temperature and especially precipitation in the week before illness, suggesting a non-food transmission route,” the report says. “These four countries may experience a doubling of Campylobacter cases by the end of the 2080s, corresponding to around 6,000 excess cases per year caused only by climate changes.”
“Considering the strong worldwide burden of campylobacteriosis, it is important to assess local and regional impacts of climate change in order to initiate timely public health management and adaptation strategies,” the researchers caution in their report.
Water environment
Other studies abroad have explored links between the general water quality and Campylobacter outbreaks. For example, a 2021 report by researchers from the Czech Republic looked at C jejuni and C coli in waste and surface waters in four different seasons.
They concluded that Campylobacter presence in water is influenced by physico-chemical parameters such as concentrations of ammonium and chloride ions. “Water environment is an alternative source of Campylobacter,” they report. The concentration of ammonium and chloride ions can be used as a basis for successful prediction of the potential occurrence of C jejuni and C coli in wastewater and surface water in future, they add.
And much earlier in 2012, scientists from Finland reported that in water environment C jejuni is exposed to a wide spectrum of temperatures, which affects its survival and potential to cause waterborne infections. “Antimicrobial resistance in C. jejuni is increasing, and minor data exist on the effect of antimicrobial resistance on the survival of C. jejuni,” it says.
This article was first published on Mongabay.
