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From the unprecedented heatwave in 2022 to the deadly Storm Eowyn just this month, climate change is already wreaking havoc on Britain’s weather.
Now, a study has revealed that humans could be next in the firing line.
Scientists from the University of Surrey say that climate change could spark outbreaks of diarrhoea in Britain.
In their study, the team found a clear link between warmer conditions and more salmonella cases in England and Wales.
Symptoms of salmonella infections include diarrhoea and stomach cramps, as well as vomiting and fever.
Infection is usually caused by eating raw or undercooked meat, poultry, and eggs or egg products or by drinking unpasteurized milk.
However, the scientists now say there’s increasing evidence weather plays a ‘crucial role’ in the transmission of the bacteria.
‘Temperature, humidity and day length [are the] key weather combination driving salmonellosis,’ warn the authors.
Scientists from the University of Surrey say that climate change could spark outbreaks of diarrhoea in Britain
‘However, the relationship between salmonellosis occurrence and climatic factors is complex and multifaceted,’ they add in their study, published in the Journal of Infection.
The study compared UK Health Security Agency data of confirmed salmonella cases in England and Wales between 2000 and 2016 with Met Office weather data from the same period.
Results showed a clear link between the spread of the bacteria and multiple weather trends that are linked with climate change.
A key weather factor linked with increased salmonellosis cases, regardless of geographical location, was warmer air temperatures – above 50°F (10°C).
Other correlated factors were relative humidity, reduced precipitation and a dewpoint temperature between 44-50°F (7-10°C).
Another factor was longer day lengths – especially between 12 and 15 hours of sunlight per day.
Climate change is not believed to affect how much sunlight we’ll get per day, but more sunlight does give the bacteria better conditions to grow.
The findings from England and Wales were also validated by analysing weather and health data from the Netherlands from between 2015 and 2019.
Salmonella, a type of bacteria that can cause food poisoning, can cause diarrhoea, fever and stomach cramps. This image shows Salmonella Typhimurium (red) invading cultured human cells
The scientists found a link between salmonella cases and higher air temperature – especially when the days were longer (with more sunshine)
What is salmonella?
Salmonella is bacteria infecting the gut. It lives in animal and human intestines and is shed through faeces.
Humans become infected most frequently through contaminated water or food.
Contamination is possible if raw and cooked foods are stored together. Symptoms of salmonella infections include diarrhoea, stomach cramps and sometimes vomiting and fever.
On average, it takes from 12 to 72 hours for the symptoms to develop after swallowing an infectious dose.
They usually last for four to seven days and most people recover without treatment.
However, dehydration caused by the illness can be life-threatening.
Source: NHS Choices
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Meanwhile, other weather factors such as air pressure, wind speed, temperature amplitude and sunshine duration showed ‘limited or no association’.
The researchers admit that they cannot be sure of causation – in other words, that the climate variables are causing the rise of salmonella infection.
Also, there may other relevant factors could also influence disease, such as proximity to livestock farms, human behaviour and other ‘environmental variables’.
For example, more people may be having barbeques in hot weather which may be increasing transmission of the bacteria via food.
However, the study offers convincing evidence that the effects of climate change are wide-reaching and could considerably affect public health in many ways.
The next steps will be to test the correlation in other countries with different ‘social and climatic conditions’ to the UK, such as a low-income country and a country from the southern hemisphere.
‘A better understanding of disease behaviour is essential for disease preparedness and prevention, especially in relation to the increasing anthropogenic impact on the environment and climate change,’ the authors conclude.
Last year the team warned that a dangerous bacteria called campylobacter will spread more quickly amid rising temperatures.
Graphical abstract from the study: The authors compared cases of salmonella infection in England and Wales with Met Office weather data
Campylobacter (artist’s impression) is one of the four key global causes of diarrhoeal diseases worldwide, according to the World Health Organisation
Campylobacter infection makes people ill with diarrhea, but also can cause abdominal pain, fever, headache, nausea and vomiting.
However, ever since the era of ancient Greek philosopher Hippocrates, there’s been a consensus that weather and climate influence the spread of diseases.
‘Getting to the bottom of why this is and what specific environmental factors drive the spread of disease is a complicated matter,’ said study author Dr Giovanni Lo Iacono.
Due to the fact that many bacteria and other microorganisms need warmth to grow, there could be countless pathogens that could proliferate under climate change.
Most bacteria that cause disease grow fastest in the temperature range between 41°F-135°F (5°C-57°C) – a range known as ‘the danger zone’.
Not all bugs thrive in the heat however – some can survive under extreme cold, highly acidic or very salty conditions.
Carbon emissions and the greenhouse effect: A primer
The greenhouse effect is the reason our planet is getting too hot to live on.
CO2 released by human activity is accumulating as an ‘insulating blanket’ around the Earth, trapping more of the sun’s heat in our atmosphere.
Without the natural greenhouse effect, heat would pass outwards from the Earth¿s surface into space – making it too cold to live. But emissions of gases such as CO2 and methane push the greenhouse effect too far – acting as a blanket that traps heat
CO2 – and other greenhouse gases – are emitted by actions such as burning fossil fuels like coal for energy, burning forests to make way for livestock and
Fertilisers containing nitrogen produce nitrous oxide emissions – another greenhouse gas.
Meanwhile, fluorinated gases are emitted from equipment and products that use these gases.
Such emissions have a very strong warming effect, up to 23,000 times greater than CO2.
Sources: European Commission/BGS/NASA
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