‘Tis the (Flu) Season. The word “flu” comes from the word influenza, which is from the Italian word influencia. In Medieval times it was believed that epidemics were due to the influence of the stars, so influencia, meaning “to flow into” referred to any disease outbreak thought to be influenced by stars. So if you are unvaccinated and get the flu, you can say it was written in the stars.
The CDC estimates influenza in the US results in 9 to 45 million illnesses, 140,000-810,000 hospitalizations, and between 12,000 to 61,000 deaths EVERY year. During the flu season 2024-2025, 216 children died. 90% were unvaccinated.
Influenza (Flu) is a contagious respiratory illness caused by influenza viruses: A, B, C and D. Influenza viruses, A and B, cause epidemics known a flu every winter in the US. Influenza A is the only influenza virus known to cause pandemics (global epidemics). When a new mutation of influenza A emerges, it can spread quickly and since it is new, people have little immunity.
Influenza A has numerous subtypes based on two proteins on the surface. More than 130 subtypes have been identified and have been given names such as A(H1N1). Making new subtypes is called reassortment and is a process by which influenza viruses swap gene subtypes. This can happen when the unvaccinated host is infected with two influenza viruses at the same time and they swap genetic material creating a new subtype.
The pandemic of 2009 the was caused by A(H1N1). The influenza A viruses A(H1N1) and A(H3N2) are circulating this year and will probably continue to circulate until they swap some genetic material and cause a new epidemic. Part of the difficulty in producing effective vaccines is trying to predict which virus will be most common and in which region of the world. Then making enough vaccine to be available where it is needed. If a new variant is produced and is spreading rapidly, a new vaccine will be needed, manufactured and evaluated.
Without testing it is impossible to know which virus is causing the flu-like illness. Many other viruses can cause respiratory flu-like symptoms including “mono”, RSV, and COVID. Testing is necessary to tell what is causing the illness. It is not stomach flu and it is not a cold.
Influenza is spread through the air by coughing, sneezing and talking just like COVID. If you touch an infected surface and your hand goes to your mouth, you can be infected. When sick with the flu, you should stay home from school/work. A person can be contagious a day before having symptoms and can be contagious up to 5-7 days after becoming sick.
Influenza vaccines are safe, effective and have been used for decades. Everyone over 6 months is recommended to get vaccinated. Antivirals should be used under medical supervision. If your child has trouble breathing, chest pain, seizures, fever over 104 degrees, call your doctor.
The American Academy of Pediatrics (aap.org) can give you updated information on vaccines.
by Sally Robinson, MD
Clinical Professor
Keeping Kids Healthy
Published 09/2025
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Also See:
UTMB Pediatrics - Pediatric Primary Care