Study Links Climate, Flu Activity
According to a recent study, seasonal flu epidemics are associated with two types of environmental conditions – cold-dry and humid-rainy. The study, led by researchers at the National Institutes of Health, presents a model based on climate that maps influenza activity around the world.
Improving existing current flu transmission models, targeting surveillance efforts and timing seasonal vaccine delivery could become easier with the study’s findings.
“The model could have a broader application, encouraging researchers to analyze the association between climatic patterns and infectious disease across a wide range of diseases and latitudes,” said researcher Cecile Viboud, Ph.D., who headed the study.
The research suggests that there is a strong seasonal cycle to human influenza infections in temperate regions, such as in the U.S. Research shows that low humidity makes it easier for the virus to survive and spread. Low temperatures and humidity also increase flu reproduction and expulsion in infected organisms. All of this means the probability of catching the virus through coughing, sneezing or breathing is more likely. In contrast, climates with high temperatures seem to block the airborne spread of the flu.
In climates like ours, low humidity could bring about the yearly winter epidemics we often see. This research can help predict when those epidemics will hit. Knowing when these events will happen will help better prepare health officials and target times when flu vaccines will be needed most.
In warmer climates, the researchers found different results. In regions with higher temperatures and major fluctuations in precipitation, flu epidemics occur during the rainy season. The study’s director suggests a possible explanation for the widespread transmission of flu in tropical climates is that during rainy seasons, people gather more indoors, increasing the likelihood of contact and spreading the virus.
“The models we used predicted the timing of peak influenza activity with 75 to 87 percent accuracy,” Viboud said.
The study’s findings are an important step in improving yearly battles with flu outbreaks. The research provides another tool in the global effort to track the spread of the flu. Next, researchers hope to examine population travel and other drivers of influenza transmission.