Infections and climate change
Climate change is profoundly altering the global environment, affecting not only natural ecosystems but also public health. One of the emerging issues in this context is the impact of climate change on infectious diseases, especially those transmitted through food and water. Among these, infections caused by the bacterium Salmonella are a major global concern. Salmonella is a genus of Gram-negative bacteria belonging to the family Enterobacteriaceae, responsible for various infections in humans and animals. There are over 2,500 serotypes of Salmonella, but the most common in humans are Salmonella enterica and Salmonella bongori. Salmonella enterica is further divided into six subspecies, with Salmonella Typhimurium and Salmonella Enteritidis being the main causes of foodborne infections. This article explores the potential link between climate change and the increase in Salmonella infections, analyzing the biological and environmental mechanisms that may explain this correlation and the implications for public health.
Salmonellosis: the disease
Salmonella is transmitted mainly through the consumption of contaminated foods, such as raw or undercooked meat, eggs, unpasteurized milk, fruits and vegetables that have come into contact with contaminated water. Salmonella can also be transmitted through direct contact with infected animals, such as poultry, reptiles and amphibians, or through contaminated surfaces. Salmonella infection, known as salmonellosis, usually manifests itself with gastrointestinal symptoms such as diarrhea, fever, abdominal cramps and nausea. The severity of symptoms can vary, and in some cases it can lead to serious complications such as sepsis, especially in the elderly, children and immunocompromised individuals.
Climate change: an emerging risk actor
Climate change is manifested through a number of phenomena, including rising global temperatures, altered precipitation patterns, and the frequency and intensity of extreme weather events, such as heat waves, floods and droughts. These changes can directly and indirectly influence the transmission of infectious diseases, including salmonellosis. One of the main effects of climate change is rising temperatures. This increase favors the growth and multiplication of bacteria, including Salmonella. Higher temperatures accelerate the life cycle of bacteria and can increase their survival in the environment, particularly in raw foods and water. Salmonella can multiply rapidly in warm conditions, especially in foods stored at inadequate temperatures. An increase in environmental temperatures can therefore favor greater proliferation of the bacteria, increasing the risk of food contamination. Global warming can prolong the survival periods of Salmonella in the environment, increasing the possibility of transmission through contact with contaminated surfaces or ingestion of contaminated water.
Irregular rainfall and water contamination
Changes in rainfall patterns, with sudden and intense rainfall, can cause flooding that contaminates water supplies with pathogens present in soil or animal feces. This contamination can include Salmonella, increasing the risk of infection for people who consume untreated water or food irrigated with contaminated water. Flooding can carry bacteria from agricultural land, where organic fertilizers such as manure are used, to drinking water sources. This increases the risk of contamination of food and water with Salmonella. During periods of drought, the concentration of bacteria in water can increase due to the reduction in water volume, exacerbating microbiological contamination.
Extreme weather events and food safety
Extreme weather events, such as heatwaves and storms, can have a direct impact on food safety. Heatwaves can cause disruptions in the cold chain, which can lead to the growth of bacteria such as Salmonella in perishable food products. Storms can damage water treatment infrastructure, increasing the risk of contamination of water supplies. Prolonged exposure of food to high temperatures, due to disruptions in the cold chain during transport or storage, can facilitate the growth of Salmonella. Extreme weather events can damage water treatment plants, compromising the quality of drinking water and increasing the risk of outbreaks of waterborne diseases, including salmonellosis.
Public health implications
Climate change can contribute to an increase in the incidence of Salmonella infections by favoring the growth and survival conditions of Salmonella. In some regions, an increase in salmonellosis cases has already been observed in association with periods of high temperatures and heavy rainfall. Research from around the world has shown a correlation between rising temperatures and increased cases of salmonellosis, suggesting that climate change may be a significant risk factor for the spread of Salmonella. Areas most vulnerable to climate change, such as those with weak health systems or inadequate food safety infrastructure, may be particularly affected by an increase in infections.
Prevention, economic impact and public education
The growing threat posed by Salmonella in a context of climate change poses new challenges for public health. Salmonella outbreaks not only have an impact on public health, but also entail significant economic costs. Salmonella outbreaks can severely damage the food sector, with product recalls, loss of consumer confidence and damage to the reputation of the companies involved. Finally, the increase in Salmonella cases can overburden health systems, with increased costs related to medical treatment, hospitalizations and outbreak management.
Educating the population on good hygiene practices and food safety is a crucial element in preventing Salmonella infections. Awareness campaigns can inform the public about the risks associated with improper food handling and storage, as well as the importance of using safe drinking water. Promoting the importance of handwashing, proper cooking of food and correct storage can significantly reduce the risk of infections. Educating the public about the links between climate change and infectious diseases can raise awareness and encourage preventative behavior.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Scientific references
European Food Safety Authority. EFSA J. 2019; 17(12):e05926.
Wu X, Lu Y, Zhou S et al. Environm Internat. 2016; 86:14-23.
D’Amato G, Cecchi L et al. Eur Resp Rev. 2014; 23(132):161-69.
Altizer S, Ostfeld RS et al. Science 2013; 341(6145):514-519.
Semenza JC et al. Crit Rev Envir Sci Technol. 2012; 42(8):857.
Lake IR, Gillespie IA et al. J Appl Microbiol. 2009; 106(2):462-70.
Havelaar AH, van Pelt W et al. Clin Infect Dis. 2007; 44(6):775.