Global warming may be reducing respiratory illnesses

Rising global temperatures over the past two decades may be responsible for a shortened season of a serious respiratory illness in the United Kingdom, according to an article in the March 1 issue of Clinical Infectious Diseases.

Respiratory syncytial virus (RSV) can cause particularly severe lower respiratory tract infections in infants and young children, sometimes resulting in pneumonia. Like the flu, RSV has a seasonal pattern, infecting the majority of people during autumn and winter.

Author Gavin Donaldson, PhD, of the University College London, examined the relationship between the RSV season and the rise in temperatures in central England from 1981 to 2004, and found that the RSV season ended earlier each year as temperatures increased. The illness season-measured by laboratory isolation of RSV and emergency room admissions due to RSV-was shortened by about three weeks per degree Celsius rise in annual mean daily temperature.

The link between respiratory disease and temperature is mysterious. "People know that there is a relationship, but don't know what's causing it," Dr. Donaldson said. Staying indoors in chilly weather might result in a higher infection rate due to our close proximity to other people. Cold air might enhance viruses' survival or affect our bodies' ability to fight off infection. "It is known that as the temperature gets colder, a lot of respiratory infections increase... There must be some link with the temperature or the season to explain precisely why this is happening," Dr. Donaldson said. However, he added, "there's no clear evidence of what the mechanism is, nor has it been shown that other respiratory illness seasons, like influenza's, have shortened due to climate change."

Global warming seems to be increasing the number of infections from other organisms, such as those that lead to food poisoning, like Salmonella and Campylobacter, Dr. Donaldson said. If global temperatures continue to rise, scientists may yet learn how much of a correlation exists between a changing climate and our health.