Here's Why The 'Unusual' Flu Season in the US Continues

The 2019-20 flu season has been odd in one particular way. So far, Influenza B/Victoria - the season's less severe version of the flu compared to Influenza A(H1N1) - has been the extra impactful stress of the flu virus.

Dr. Bryan Lewis, a professor at the Biocomplexity Institute at the University of Virginia, told AccuWeather the flu season has been quite unusual. "This is probably the most cases caused by Influenza B in any season in the remaining 20 years," he noted.

Hospitalization and death are less frequent than with Influenza A, while Influenza B causes substantial illness in those stricken.

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Although Influenza A did ultimately overtake Influenza B this week to account for almost all of flu pastime in the United States for the first time this season, incidence continues to decline. According to the Biocomplexity Institute researchers, the rate could lead most of the states returning to low degrees in the next two to four weeks.

Noting the significant decline in some regions, Lewis said the researchers count on some small surge in interest in some places. Most areas might take a few extra weeks to 'leave' the season, and a number of the states will stretch out with the secondary peaks.

According to the Centers for Disease Control and Prevention (CDC), visits to health care carriers for influenza-like illnesses (ILI) decreased from 5.7 percent last week to 4.7 percent this week.

 Flu activity remains high, CDC noted - and above the countrywide baseline of 2.4 percent - but the Biocomplexity Institute researchers data says that 46 states have decreased inactivity.

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The CDC estimates that up to now this season, there have been at least 13 million flu illnesses, 120,000 hospitalizations, and more than 6,000 deaths from the flu. It's the 9th subsequent week flu season which is above baseline normal; remaining year, tiers of ILI inside the U.S. have been at or above baseline for 21 straight weeks.

Several states scattered among Texas to South Carolina may be entering the final weeks of active transmission, having skilled each A and B waves with now declining activity, researchers at the Biocomplexity Institute noted.

Flu season in the United States commonly starts in October, peaks between December and February, and lasts into March - although activity could end by May. 

Peter Palese, a microbiologist in New York's Icahn School of Medicine, told the New York Times that flu viruses are more stable in cold air, and the low humidity allows the virus particles to remain within the air. He added there are only a few cases of flu in the tropics.

AccuWeather founder and CEO Dr. Joel Myers said their agency believes that weather and the sunshine intensity are vital factors in the flu season. He explained there is no flu to talk of during the summer because the sun is powerful and the weather is warm.