Left unchecked, global warming may shape future epidemics
Rising global temperatures may escalate antibiotic resistance, as well as increase the risk of future epidemics, including those caused by dengue fever, according to researchers.
Climate change has been identified by WHO as a major cause of emerging infectious diseases, and two recently published studies evaluated the potential effects it may have on public health.
Felipe J. Colón-González, PhD, senior research associate at the University of East Anglia’s School of Environmental Sciences, and colleagues found that adhering to The Paris Agreement, which intends to hold the rise in the global mean temperature below 2°C (35.6°F) and eventually limit it further to 1.5°C (34.7°F) above preindustrial levels, would potentially reduce dengue fever cases by 2.3 million cases per year. An additional study led by Derek R. MacFadden, PhD, from the University of Toronto’s department of medicine and the Harvard T.H. Chan School of Public Health, found that rising regional temperatures may contribute to the spread of antimicrobial resistance.
Dengue fever and global-mean temperature
Currently, dengue fever is endemic in over 100 countries, and WHO estimates that there are approximately 100 million cases per year.
“Climate change will increase the number of dengue infections in Latin America and the Caribbean,” Colón-González told Infectious Disease News. “Clinicians should be aware that dengue incidence will not only increase in areas where it is currently present but also in areas where incidence is low or absent.”
Taking into account dengue fever cases in Latin America, researchers used computer models to investigate the impact of global mean temperature at 1.5°C (35.6°F), 2°C (34.7°F) and 3.7°C (38.66°F) above preindustrial levels at baseline (1961 to 1990), middle of the century (2050s ) and the end of the century (2100).
According to the study, the increase in dengue fever cases will most affect southern Mexico, various Caribbean island states, northern Ecuador, Colombia, Venezuela and the coastal Brazilian states
Colón-González and colleagues said limiting the increase in the global mean temperature to about 2°C (35.6°F) could possibly reduce the number of dengue cases by 0.8 (95% CI, 0.3-2) million cases per year for the 2050s period. Similarly, dengue fever cases could drop by 2.8 (95% CI, 0.8-7.4) million for the 2100 period.
Furthermore, if global warming efforts adhere to the Paris Agreement and the global mean temperature increase is limited to 1.5°C (34.7°F) above preindustrial levels, dengue fever cases would drop an additional 0.3 (95% CI, 0.1-0.5) million cases per year by the 2050s period and 0.5 (95% CI, 0.2-1.1) million cases per year by the 2100 period.
According to the study, rising temperatures could potentially contribute to an additional 7.5 (95% CI, 3.1-14.9) million dengue fever cases per year by the 2050s compared to the estimates for the baseline period.
Colón-González and colleagues emphasized that public health risks may significantly decrease if the increase of global mean temperature is held at about 1.5°C (34.7°F) above preindustrial levels.
“Encourage patients to engage on climate change issues and talk to them about the potential effects on their health,” Colón-González said. “Engage in activities to reduce climate change and participate in activities promoting climate change education and advocacy.”
Antimicrobial resistance and rising temperatures
The CDC estimates at least 23,000 people die each year due to infections that have developed resistance to antibiotics. Antimicrobial resistance — which has been associated with inappropriate prescribing and antibiotic overuse — is a serious threat to global public health, according to WHO.
“Increasing local minimum temperature is associated with increasing antibiotic resistance across the United States for common bacterial pathogens,” MacFadden told Infectious Disease News. “Warmer regions throughout the United States have a higher prevalence of common bacterial infections with resistance to typical antibiotics.”
MacFadden and colleagues evaluated the role climate, specifically temperature, has on the distribution of antimicrobial resistance in different regions across the United States.
Using information from hospitals, laboratories and surveillance units, researchers created antibiotic resistance indices and developed a database of antibiotic resistance patterns across the United States. Over 1.6 million clinically relevant bacterial pathogens from 41 states were represented in the final data set for 2013 to 2015.
According to the study, an increase in minimum temperature was associated with an increase in antibiotic resistance across most classes of antibiotics and pathogens. Specifically, an unadjusted analysis found that an increase in temperature across all regions by 10°C (50°F) was associated with a 5.1% increase in antimicrobial resistance for E. coli (P < .0001), 3.4% for K. pneumoniae (P < .0001) and 3.1% for S. aureus (P = 0.002), which are the most common antimicrobial resistant pathogens. When adjusted for acquisition source, prescription rate, population density and laboratory standard, the 10°C (50°F) increase in temperature was associated with a 4.2% (P < .0001), 2.2% (P < .0001) and 2.7% (P = .21) increase in antibacterial resistance for E. coli, K. pneumoniae and S. aureus, respectively.
MacFadden and colleagues noted that more research is required but suggested regional temperature and future climate change may accelerate the spread of antimicrobial resistance.
“Climate may play a role in this distribution, and if this is the case, we may see a disproportionate increase in antibiotic resistant organisms originating from warmer densely populated areas,” MacFadden said in the interview. “Moreover, our current forecasts of the burden of antibiotic resistance may be underestimated as a result.”
Last year, President Donald J. Trump issued an executive order that rolled back Environmental Protection Agency pollution standards and pulled the U.S. out of The Paris Agreement, despite evidence of the harmful effects climate change can have on health. Global warming and rising temperatures may create new challenges for ID clinicians by increasing infection risk in vulnerable populations and advance the spread of antimicrobial resistance.
The EPA did not immediately respond to a request for comment from Infectious Disease News. – by Marley Ghizzone
CDC. Antibiotic/Antimicrobial Resistance. https://www.cdc.gov/drugresistance/index.html. Accessed May 30, 2018.
WHO. Antimicrobial resistance. http://www.who.int/news-room/fact-sheets/detail/antimicrobial-resistance. Accessed May 30, 2018.
Disclosures: Colón-González and MacFadden report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.