From the Guidelines
There is no evidence of increased flu cases in 2025, as we are currently in 2024 and cannot predict future flu seasons with certainty. Flu seasons vary in severity from year to year based on several factors including which virus strains are circulating, how well-matched the annual vaccine is to those strains, population immunity levels, and public health measures. When flu seasons are particularly severe, this can be due to viral mutations creating strains that existing immunity doesn't fully protect against, lower vaccination rates, reduced adherence to preventive measures like handwashing, or environmental factors that favor viral transmission. To protect yourself from flu, get the annual influenza vaccine, practice good hand hygiene, avoid close contact with sick individuals, and consider wearing masks in crowded indoor settings during peak flu season. If you develop flu symptoms, antiviral medications like oseltamivir (Tamiflu) can help reduce severity and duration if started within 48 hours of symptom onset, typically prescribed as 75mg twice daily for 5 days for adults 1. Some key factors that influence the severity of flu seasons include the predominant virus strains, vaccination coverage, and the effectiveness of the vaccine against circulating strains, as highlighted in recent studies 1. For instance, the 2022-2023 flu season was characterized by moderate severity, with influenza B/Victoria and influenza A(H1N1)pdm09 being the predominant strains, and a vaccination coverage of 62.3% in children 1. Understanding these factors can help inform preventive measures and treatment strategies to reduce the impact of flu seasons on public health. Key preventive measures include:
- Getting the annual influenza vaccine
- Practicing good hand hygiene
- Avoiding close contact with sick individuals
- Considering wearing masks in crowded indoor settings during peak flu season
- Starting antiviral medications like oseltamivir (Tamiflu) within 48 hours of symptom onset, if prescribed by a healthcare provider. It's essential to stay informed about the latest developments and recommendations from reputable sources, such as the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP), to make informed decisions about flu prevention and treatment 1.
From the Research
Possible Causes of Increased Incidence of Influenza
- The increased incidence of influenza cases this year could be due to various factors, including the continuous antigenic drift/shift of circulating strains of influenza virus, which may lead to antigenic mismatch between circulating and vaccine strains and reduced vaccine effectiveness 2, 3, 4.
- The severity of pandemic influenza depends on multiple factors, including the virulence of the pandemic virus strain and the level of pre-existing immunity 2.
- Inadequate vaccination coverage, vaccine shortages, and mismatches with circulating strains may also contribute to the increased incidence of influenza cases 5.
- The rapid variability of the virus poses challenges in providing extended protection beyond a single season, which could lead to an increase in influenza cases 6.
Vaccine-Related Factors
- The efficacy of influenza vaccines is not optimal and can be dramatically low in the case of an antigenic mismatch between the vaccine and the circulating virus strain 2.
- Current preventative strategies of vaccination against influenza virus often provide incomplete protection due to the continuous antigenic drift/shift of circulating strains of influenza virus 3.
- Emerging approaches to combat influenza include the development of universal influenza virus vaccines that provide protection against antigenically distant influenza viruses, but these vaccines need to be tested in clinical trials to ascertain their effectiveness 2, 6.
Global Patterns of Seasonal Influenza Activity
- Seasonal influenza viruses undergo unpredictable changes, which may lead to antigenic mismatch between circulating and vaccine strains and to a reduced vaccine effectiveness 4.
- The global epidemiology of influenza shows that the median proportion of influenza cases caused by type A viruses was 75.5%, with epidemic peaks typically occurring during winter months in Northern and Southern hemisphere countries 4.