If you think you have a horrible flu, there’s a good chance it’s just a cold. According to a new study, flu-like illness can be caused by many pathogens, making it difficult to assess how often people are actually infected by influenza, but it’s clear that adults over the age of 30 get it only about twice a decade.
That’s not the case with children, who get flu on average every other year, shows a research that gathered blood samples from volunteers in Southern China and looked at antibody levels against influenza strains that circulated from 1968 to 2009.
“There’s a lot of debate in the field as to how often people get flu, as opposed to flu-like illness caused by something else. These symptoms could sometimes be caused by common cold viruses, such as rhinovirus or coronavirus. Also, some people might not realize they had flu, but the infection will show up when a blood sample is subsequently tested. This is the first time anyone has reconstructed a group’s history of infection from modern-day blood samples,” said Dr Adam Kucharski, who worked on the study at Imperial College London before moving to the London School of Hygiene & Tropical Medicine.
The exact frequency of infections vary depending on background levels of flu and vaccination, but the findings show that infections become less frequent as people get older, probably because children spend more time with others. But the team of researchers from the UK, the US and China also developed a mathematical model of how the immunity changes in time, as people encounter different strains of flu. They explained that the immune system responds by producing antibodies that have memories of strains encountered before and the strains from the childhood or early adulthood evoke stronger immune responses.
Because of these findings, scientists will be able to make predictions about how the virus will change in the future and they will also see how old strains will influence the way vaccines work and how effective they will be.
“What we’ve done in this study is to analyze how a person’s immunity builds up over a lifetime of flu infections. This information helps us understand the susceptibility of the population as a whole and how easy it is for new seasonal strains to spread through the population,” concluded Dr Adam Kucharski.