Jakarta. The term superflu has gained attention amid rising influenza cases overseas. Health experts say it is not a new disease, but a public label commonly used for flu outbreaks linked to Subclade K, a new mutation of the Influenza A (H3N2) virus.

Subclade K has been reported as a dominant strain in the United Kingdom, Japan, and parts of the United States. In New York City, infections were estimated at around 71,000 cases in a single week, heightening public concern.

Researchers first identified Subclade K in June 2025. The variant has shown rapid transmission, compounded by flu seasons arriving four to five weeks earlier than usual in countries such as the UK and Norway. While this has made the current wave appear more aggressive, scientists stress that influenza viruses mutate routinely. Nicola Lewis, director of the World Influenza Centre in London, said there is no clear signal of unusual viral evolution at this stage.

In Indonesia, authorities have raised vigilance. The Health Ministry said whole genome sequencing completed on Dec. 25, 2025 confirmed Subclade K has been detected through the national ILI-SARI sentinel surveillance system since August 2025. As of Jan. 4, 2026, 62 confirmed cases had been recorded across eight provinces, with the highest numbers in East Java, South Kalimantan, and West Java.

Symptoms and How It Differs From the Common Flu

According to Mitra Keluarga Hospital, superflu symptoms typically appear suddenly, two to three days after exposure. The complaints may resemble common flu but tend to be more severe and last longer, often disrupting daily activities.

Symptoms to watch for include high fever, persistent dry cough, headache, runny nose, muscle aches, chills, extreme fatigue, reduced appetite, and eye discomfort such as pain, watering, or light sensitivity. In children, symptoms are often more general and may come with additional complaints.

Common flu can also start abruptly and cause fever, muscle pain, headache, fatigue, and dry cough. However, the key differences with superflu lie in its higher transmissibility and symptom severity. The variant is reported to spread more easily, with one infected person potentially transmitting the virus to two or more others. Patients may experience very high fever reaching 39–40 degrees Celsius, extreme exhaustion, a lingering dry cough, and more intense headaches, with illness lasting longer and leaving the body significantly weaker.

By contrast, common flu usually affects the respiratory tract with symptoms that still allow light activity and rarely causes prolonged or severe complaints like those associated with Influenza A H3N2 Subclade K.

The Jakarta Health Agency (Dinkes) has urged residents to maintain clean and healthy habits, including regular handwashing, wearing masks when sick, proper cough etiquette, adequate rest, balanced nutrition, and regular exercise.

Pramono Anung Wibowo said he has instructed the agency to prepare anticipatory measures, although no cases have been found in Jakarta so far.

Health officials emphasize there is no cause for panic, but the surge is a reminder that influenza should not be underestimated, especially for vulnerable groups.