Preschoolers may signal the arrival of flu season: Thirty days after hacking 3- and 4-year-olds start showing up in doctors’ offices and emergency rooms, flu-ridden adults follow. It’s a provocative discovery sure to bolster growing calls to vaccinate more healthy children against influenza – to help keep the misery from spreading. Moreover, researchers using a system that almost instantly tracks Boston-area health care found that a spike in respiratory illness among youngsters less than 5 predicts that about five weeks later, influenza-related deaths among the elderly will peak. The study doesn’t prove preschoolers actually drive each winter’s flu epidemic, just that they’re harbingers for waves of illness. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! AD Quality Auto 360p 720p 1080p Top articles1/5READ MOREThe top 10 theme park moments of 2019 “What we think is most likely is that 3- and 4-year-olds are early spreaders of influenza because of the preschool setting,” said John Brownstein, an epidemiologist at Children’s Hospital of Boston and co-author of the new study. Brownstein calls the close quarters of preschool and day care, full of kids who don’t yet cover their sneezes and are apt to pick their noses, “hotbeds of infection.” Regular schools are too, caution other experts who cite evidence that school-age children might be the biggest influenza spreaders. Older children may have better hygiene, but the 5- to 18-year-old population is much larger and more active in the community, giving it greater contact with the elderly who are most vulnerable to influenza, explains flu specialist Ira Longini, a biostatistician at Emory University. Healthy children older than 2 aren’t on the government’s list of flu-shot targets each year because they’re typically strong enough to fight off the virus without complications. Parents can choose to get them vaccinated anyway, as supplies allow.