When does flu season start
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Understanding the Start of Flu Season
Global Variations in Flu Season Start
Europe: Late Fall Onset
In Europe, the flu season typically begins in late fall. For instance, the 2014/15 influenza season started in week 50 of 2014, with influenza A(H3N2) viruses being the dominant subtype . Similarly, the 2008-09 season commenced in week 49 of 2008, also dominated by the A(H3N2) subtype . The 2013/14 season saw its onset with the influenza A(H1)pdm09 virus being the most prevalent subtype .
United States: Fall to Early Winter
In the United States, the flu season generally starts in the fall and continues through the winter and spring months. For example, during the 2014 season, influenza activity increased starting mid-October through December . The 2013 season saw a similar pattern, with activity increasing from mid-November through early December . The 2021-22 season began to see an increase in influenza activity in November, which remained elevated until mid-June .
Australia: Early Start
Australia has experienced early starts to its flu seasons. In 2019, the flu season began around the end of March, about two months earlier than the previous five years . This early onset prompted concerns about a potentially severe season.
South Africa: Winter Period
In South Africa, the flu season spans the winter period, typically starting in May and ending in September. This timing is based on statistical intensity thresholds and data from public-sector hospitalizations and private-sector medical insurance claims .
Finland: Impact of COVID-19
The 2020-21 influenza season in Finland did not begin as expected, largely due to the impact of COVID-19 lockdowns and nonpharmaceutical interventions. Despite looser restrictions during the second wave of COVID-19, the influenza season was effectively interrupted .
Tennessee: Early Pediatric Cases
In Tennessee, the 2022-23 influenza season began earlier than usual, in late September, with high pediatric hospitalization rates observed in November . This early start was characterized by increased influenza activity among children, highlighting the importance of early vaccination and preventive measures.
Conclusion
The start of the flu season varies significantly across different regions. In Europe and the United States, it typically begins in the fall, while in Australia, it can start as early as March. South Africa sees its flu season during the winter months, from May to September. The COVID-19 pandemic has also influenced the timing and intensity of flu seasons, as seen in Finland. Understanding these variations is crucial for effective public health planning and vaccination strategies.
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