4 signals from Southern Hemisphere about coming US flu season

Flu season is underway in the Southern Hemisphere, and public health experts are looking at early data that may signal what could be ahead for the U.S. this fall. One notable change so far, data shows there's an uptick in influenza B, one expert told Becker's.

"One of the interesting things that are coming out and are a little bit distinct from last year, is that about one-third of the cases are influenza B strains," Seema Lakdawala, PhD, associate professor of microbiology and immunology at Emory's School of Medicine told Becker's. "Influenza A is still the predominant strain making up 70 percent of cases, but seeing 30 percent are influenza B — that is a little bit different from what we typically see. Usually we'll see either influenza A and then influenza B peak, but right now we're seeing co-circulation of both." 

What does that mean for vaccines? Right now, it's too early to tell, Dr. Lakdawala said. But more data will emerge about vaccine efficacy in the coming weeks and that information will be important for U.S. public health officials to understand what changes they may need to make before rolling out vaccines in the U.S. this fall. 

"Right now, it's unclear whether there's an emergence of something that has sort of drifted outside of the vaccine components that we may want to take into account or be aware of, but I think that data will begin to come out probably within the next month or two months," she said. 

Currently, hospitalizations and cases are both on the rise in the southern half of the globe, which is actually expected at this stage in the flu season, according to Dr. Lakdawala. The individuals who are being hospitalized are also consistent with the typical populations that the flu tends to affect most: the youngest and oldest members of the population.

"Most of the people that are admitted to the hospitals are over 55," she said. "But it's still early in the season, and we don't have all of the demographic data just yet, so that may shift." 

While the early data shows an increase in hospitalizations and cases at the moment, Dr. Lakdawala says this is still in line with normal five-year data, after the world saw flu cases drop for a few years during COVID-19. 

She recommends clinicians pay close attention to the following to prepare for the upcoming viral season: 

  1. Pay attention to vaccine efficacy data once it comes out. That data will "be important to see how that fits with the components for the Northern Hemisphere vaccine," Dr. Lakdawala said.

  2. Another 'tripledemic' could occur in the U.S., if mitigation measures aren't in place. The flu, COVID-19 and respiratory syncytial virus "can co-circulate because populations are naive to all of them," she said. "And without mitigation measures the transmission efficiency of each of them will slightly vary."

  1. Taking actions to mask, social distance and get vaccinated when it becomes time as months get colder, will hold the key to how the U.S. trends during the flu season this coming fall. Specifically consider masking in closed spaces.

  2. It's also important to think about ventilation systems within hospitals, health systems and really any closed spaces where individuals may gather, Dr. Lakdawala said. 

"We really can curtail influenza transmission, just by implementing some of the tools that are already in our toolbox that weren't burdensome. …" she said. "Influenza really is a large public health threat. We really need to remember the lessons we've learned from the COVID-19 pandemic, and not forget that the things we learned were effective and helped with our desire to go back to a more normal way of life."

Last year, the CDC reported that the U.S. had between 300,000 and 650,000 flu hospitalizations and saw between 27 million and 54 million cases. 

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