Forget the 3-day flu — this one stays for 10

Deryn Theone L. Hipe

It started as just another flu season — until the symptoms refused to leave.

What began as a routine illness is now being linked to a newly identified flu variant that is changing how long — and how hard — the flu hits. Behind this is the variant officially termed as “subclade K,” otherwise known as the super flu. 

Subclade K is a mutated variant of the Influenza A H3N2 subtype, which is responsible for seasonal flu in humans. Virus mutations occur in the process of replication, when a virus continuously copies itself to survive in its host cell. These mutations can change how the virus behaves.

In the super flu’s case, this particular mutation has made the virus more problematic for humans, causing prolonged symptoms that last for 7–10 days compared to the usual 3–4 day period observed in regular flu cases. This also makes it more severe for high-risk populations, such as the elderly, children, and pregnant women.

“There are genetic differences between the circulating influenza viruses and the strains included in the vaccines; the seasonal influenza vaccine may still provide protection against drifted viruses and the other virus strains included in the vaccine,” the World Health Organization (WHO) noted.

In the Philippines, there have been a total of 17 detected cases of the super flu in 2025, according to Health Secretary Teodoro Herbosa. However, Herbosa also stated that all of them have recovered.

The Department of Health (DOH) says that the super flu should not alarm Filipinos, as it is just a usual “seasonal infectious disease.” To avoid contamination, the DOH recommends the public get flu vaccines and to observe public health precautions, such as covering one’s mouth when coughing.

While it may be another common virus, the emergence of the super flu shows that even familiar seasonal illnesses can evolve in ways people should not ignore.