Tracking flu trends below the equator helps medical teams and public health officials prepare for flu season up north, although the influenza virus is so adept at changing that predictions are helpful but not a guarantee of what’s to come, said Paula Couto, MD, an influenza surveillance epidemiologist with the Pan American Health Organization, which is a regional office of the World Health Organization for the Americas.
She said the interim report, which used data from Argentina, Brazil, Chile, Paraguay, and Uruguay, can help with preparations such as estimating this season’s needs for health services and also demand for antiviral drugs used to treat flu.
“Of course, influenza is a tricky virus because it has pandemic and epidemic potential, so it may not necessarily be the same [between hemispheres], but that’s why we are always monitoring and alert about these viruses,” said Couto, who also co-authored the CDC report.
There is no official start date for flu season each year in the U.S. The start date varies because it’s usually determined after the fact, based on a combination of factors such as increasing rates of positive flu tests and hospitalizations. That tends to be in late November.
“In the U.S., we tend to see the flu season start in the Southeast, like in Florida and Texas, and surrounding states, and then we kind of see it spread from there,” said Regan. “Usually it doesn’t take too long, like we’re talking a couple weeks max … because people move a lot and people are much more mobile nowadays than they were during the height of the pandemic.”
The U.S. appears to be on the verge of flu season.
The CDC indicated that flu cases are on the rise in the Southeast, as well as in South Central and West Coast states, according to the agency’s latest weekly flu report. Currently, about 4% of flu tests are coming back positive nationally. Already, one child has died due to influenza. Children are one of the groups with low flu vaccination rates in the U.S. and around the world, Regan noted.