It has long been observed that flu seasons in the northern hemisphere tend to last over autumn and winter, while in regions closer to the equator, they tend to have a year-round prevalence.
A group of Italian researchers believe that the sun – specifically its UV rays, which are known to inactivate various pathogens – holds the key. This periodic change in UV radiation over the seasons resonates with another cyclical event – the loss of resistance in the host over half a year of antigenic drift. The researchers incorporated these effects into a series of models, which reflect the seasonality of airborne respiratory diseases.
“From an epidemiologic point of view, these models clarify an important and long-standing mystery: why do influenza epidemics disappear every year when the number of susceptible individuals is still very far from that needed to trigger the herd immunity mechanism?” said Mario Clerici, Immunologist at the University of Milan and the Don Gnocchi Foundation.
“The Italian data of the SARS-CoV-2 pandemics can also be described accurately by our model,” said Fabrizio Nicastro, INAF researcher and PI of the work, “but the predictive power of the model depends critically (other than on the implementation of new restriction measures) on the exact UV-B/A lethal doses for the COVID-19 virus, which our collaboration is about to measure.”
Source: Medical Xpress
