Temporal Shifting of Influenza Subtype Dynamics in Pakistan Following the COVID‐19 Pandemic: A 10‐Year FluNet Analysis, 2015–2024
Ahmar Jan Qureshi, Muhammad Riyyan Tariq Tagga, Hussnain Ali, Aliza Tariq, Modibo YattassayeABSTRACT
Background
The COVID‐19 pandemic and associated nonpharmaceutical interventions caused unprecedented suppression of influenza circulation globally. Pakistan, with its high population density and evolving surveillance capacity, lacks long‐term data on post‐COVID‐19 influenza patterns, essential for guiding vaccine policy.
Methods
We extracted weekly virological data for Pakistan from the WHO FluNet platform (January 1, 2015, to December 31, 2024). The study period was divided into pre‐COVID‐19 (2015–2019), COVID‐19 disruption (2020–2021), and post‐COVID‐19 (2022–2024) phases. Outcomes included type A versus B proportion, subtype distribution (A[H1N1]pdm09 vs. A[H3]), positivity, peak intensity, and season duration (weeks with positivity ≥ 10%). Statistical comparisons used chi‐square for subtype distribution and Kruskal–Wallis for peak intensity.
Results
We analyzed 6522 positive specimens from 79,484 tested (10,781 pre‐COVID‐19; 14,687 during COVID‐19 disruption; 54,016 post‐COVID‐19). Influenza A declined from 94.2% to 71.7% then rose to 77.5%; influenza B increased from 5.7% to 28.3%, remaining at 22.5% ( p < 0.001). A(H3) dominated during the COVID‐19 disruption (98.8%); A(H1N1)pdm09 regained dominance post‐COVID‐19 (58.8%), though A(H3) remained higher than pre‐COVID‐19 (41.2% vs. 33.3%). Peak intensity differed ( p = 0.047): pre‐COVID‐19 33.3%–67.6%; COVID‐19 disruption 14.0%–17.6%; and post‐COVID‐19 19.8%–37.8%. Season duration was 1 week in 2020 and 3 non‐consecutive weeks in 2021, versus 10–16 weeks pre‐COVID‐19, recovering to 7–13 weeks post‐COVID‐19.
Conclusion
The COVID‐19 pandemic induced a lasting shift in Pakistan's influenza epidemiology, with persistently elevated influenza B and reshaped A subtype balance. These findings are consistent with the global disappearance of B/Yamagata and support consideration of trivalent vaccine formulations, though antigenic and genetic data remain necessary to confirm vaccine match.