Spring Flu Surge: What to Know About Rising Influenza A(H1N1)pdm09 and Type B Cases

As spring approaches, health officials are monitoring a potential increase in influenza cases, particularly those caused by influenza A(H1N1)pdm09 and type B viruses. While overall respiratory illness rates remain relatively low, laboratory data indicates a growing proportion of these strains, raising concerns about a possible new wave of infections.

Rising Influenza Strains

Recent reports from Rospotrebnadzor, the Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing, highlight an increase in the proportion of influenza A(H1N1)pdm09 and influenza B viruses detected in laboratory samples . This increase is occurring even as the overall number of acute respiratory viral infections (ARVIs) and influenza cases remains generally low.

Understanding Influenza A(H1N1)pdm09 and Influenza B

Influenza A(H1N1)pdm09, often referred to as “swine flu,” is a strain of the influenza A virus that caused a global pandemic in 2009. Influenza B viruses can as well cause seasonal epidemics, and while generally less severe than influenza A, they can still lead to significant illness, especially in vulnerable populations.

Recent Research and Findings

Research conducted by the Smorodintsev Research Institute of Influenza in Saint Petersburg has been assessing the intense influenza A(H1N1)pdm09 epidemic and vaccine effectiveness . Studies have also investigated severe influenza cases in Russia during the 2022-2023 flu season, noting the prevalence of influenza A(H1N1)pdm09 . Further analysis of influenza viruses that caused epidemic increases in morbidity during 2022–2023 identified significant activity of influenza A(H1N1)pdm09, which was later replaced by influenza B virus activity .

What Does This Indicate for Spring Travel?

The observed increase in these influenza strains suggests a potential for increased illness as spring travel increases. While the current rates are low, the emergence of these strains could lead to a new wave of morbidity.

Key Takeaways

• Influenza A(H1N1)pdm09 and influenza B viruses are becoming more prevalent.
• Overall rates of respiratory illness are currently low, but this could change.
• Increased travel in the spring may contribute to the spread of these viruses.