When will flu and RSV peak?

(NEXSTAR) – While COVID-19 cases have remained flat (albeit pretty high) over the past two months, two other viral infections have taken off: influenza and respiratory syncytial virus, better known as RSV. Tracking by the Centers for Disease Control and Prevention shows both illnesses ramping up quickly since early fall — shaking up the transmission patterns we’ve seen the past few years. While the viruses that cause the flu circulate year-round, sickness usually peaks in February in the U.S., according to the CDC. This year, influenza started circulating earlier than normal, and it may peak earlier, too. Dr. Andrew Pekosz, a virologist and professor at Johns Hopkins Bloomberg School of Public Health, believes the U.S. is still in the “early stages” of a surge in influenza cases, he told Nexstar.

“For influenza, we are still on the upside of the curve, and we really have no idea what the peak number of cases will be and when that will happen,” he said. As of last week, 33 states recorded “high” or “very high” flu activity. Kinsa, a company that forecasts illness peaks using thermometer data and medical data, says the flu is “critical and rising” as of late November. Kinsa’s model projects illness peaking in mid-December, much earlier than a normal year. Less testing over the Thanksgiving holiday may make it look like flu numbers are dropping off, Pekosz explained, but he expects the case numbers to jump back up again in the next few weeks.

“With RSV we seem to be hitting a plateau,” said Pekosz. “Case numbers have not increased significantly for a couple of weeks, but they’re still at a very high level. So the burden of RSV is still great, but we may be closer to the peak there than we are with flu.” Kinsa’s model agrees with Pekosz, showing RSV cases starting to decrease despite
hospitalizations remaining high. Prior to the pandemic, RSV spread usually started to pick up between September and November, peak between December and February, and drop off in the spring. In 2021, things looked different. As COVID restrictions eased and social distancing dissipated, we saw a summer peak of RSV.

This year, we appear to be getting closer to the pre-pandemic normal pattern, but the CDC warns that it’s “too soon to predict when the previous seasonal patterns will return.” All three viral illnesses — COVID, influenza and RSV — have the potential to increase after the Thanksgiving and Christmas holidays, simply because people are getting together more often and in bigger groups. “This virus actually knows how to get us. It follows humans, meaning that we are going to be together, we’re going to be in those spaces with poor ventilation, and COVID-19 loves that,” Dr. Ilan Shapiro, chief medical affairs officer at AltaMed in Los Angeles, recently told Nexstar. He added that influenza and RSV also spread quickly under those conditions. Both doctors stressed the importance of getting tested if you feel sick to ensure you get proper treatment. “For both flu and for COVID, we have antivirals that work if taken early after signs of symptoms,” said Pekosz. “So particularly if you’re in a high-risk group, it’s good to know that. … Those are important tools that we really have to keep using.”