Oct 28, 2024 · Learn about the flu season, including how CDC track flu activity and when flu activity occurs and most often peaks.

This work will establish an important baseline to better understand factors that influence seasonal influenza dynamics and how COVID-19 may have affected seasonal activity and influenza virus types, subtypes, and lineages circulation patterns.

There are four types of influenza viruses: A, B, C, and D. Influenza A and B tend to spread between people around the world each year. In contrast, influenza C and D mainly infect birds and other animals.

A Weekly Influenza Surveillance Report Prepared by the Influenza Division. This system monitors visits for respiratory illness that includes fever plus a cough or sore throat, also referred to as ILI, not laboratory confirmed influenza and may capture patient visits due to other respiratory pathogens that cause similar symptoms.

Influenza virus subtypes are distinguished based upon the antigenic properties of two surface glycoproteins: hemagglutinin (H) and neuraminidase (N), which promote and coordinate host cell entry and exit, respectively.

The mechanisms that shape the global seasonal patterns of influenza virus, respiratory syncytial virus, parainfluenza virus, and metapneumovirus remain unclear. Possible mechanisms include contact rates between susceptible and infected hosts, virus survival, and host immunity.

Feb 1, 2025 · Our findings enhance the understanding of the COVID-19 pandemic's short-term impact on influenza seasonal patterns and highlight the importance of robust surveillance following an emerging infectious disease pandemic to inform preventive and control strategies.

Early findings from the WHO RSV surveillance pilot based on the GISRS suggest annual seasonal patterns for of RSV circulation that overlap with influenza. RSV surveillance needs to be continued for several more seasons to establish seasonality patterns to inform prevention and control strategies.

Nov 19, 2010 · Recent reports of substantial levels of influenza virus activity and well-defined seasonality in tropical regions, where warm and humid conditions often persist year-round, have rendered previous hypotheses insufficient for explaining global patterns of influenza.

Different patterns of influenza incidence in a total population, caused by different patterns of social interaction among four etiologically distinct age groups: children <5 years (black lines), children 6 to 20 years (red lines), adults (green lines), and the elderly (blue lines).