Flu Cases Surge in Various Countries, Beware of Superflu

JAKARTA - The phenomenon of superflu that is widely discussed by the public actually refers to the influenza virus of the A type subvariant H3N2 with the K subclade.

Flu cases have increased in recent weeks, including in Indonesia. The spread is so fast that people call it a superflu, although this term does not appear because of official medical terminology.

Not only in Indonesia, the spread of this seasonal flu outbreak has also occurred in a number of countries, such as the United Kingdom. According to the British Medical Journal (BMJ) analysis on December 10, 2025, the influenza A H3N2 subklad K variant is the cause of an early and severe flu season in the UK.

Official data in the UK shows that the percentage of positive flu cases has started to increase in the country since October. This surge came much earlier than the previous three years in a row. Significant flu cases are now reported throughout Great Britain, including Scotland, where the number of hospitalized patients increased by 70 percent in just one week.

Although it is fast spreading, the Ministry of Health emphasized that the severity of the symptoms of this variant is still the same as seasonal flu. In Indonesia itself, the situation is still under control.

Pediatric pulmonologist and respirologist subspecialist who is also a member of the Coordination Working Unit (UKK) of the Indonesian Pediatric Association (IDAI) Nastiti Kaswandani said that the term superflu, as many people say today, is actually less appropriate.

The flu that is now widely discussed by the public is actually a type of influenza type A subvariant H3N3 with subklad (subclade) K. The type of virus, which is suspected to contribute to the spike in flu cases in several countries, was eventually called a superflu.

"The word superflu has caused panic because this term is actually not in medical terminology. The problem is, maybe, one of the causes of this superflu term is because of its rapid transmission. One person can infect two to three people or more around him, it is estimated that this variant can be more contagious, but there is no research," said Nastiti in a discussion "Recognizing and being aware of superflu" which was followed online.

Subklad K is a new variant that was first identified by the US CDC in August 2025. According to the US Centers for Disease Control and Prevention (CDC), this strain is responsible for very high flu cases in New York, Rhode Island, Colorado, and Louisiana, as well as in several states.

The CDC estimates that there have been at least 7.5 million cases, 81,000 hospitalizations, and 3,100 deaths from the flu so far in the US. That includes at least eight child deaths.

"The UK has been hit pretty hard by this, as have Europe and Australia," said Neil Maniar, director of the Master of Public Health program at Northeastern University, in a written statement.

"This is going to be a very difficult flu season."

If totaled, the variant has spread in at least 80 countries. In Indonesia, this variant has been detected since August 2025. At least, until the end of December 2025, 62 cases of influenza A subklad K have been found in eight provinces. The three provinces with the most cases are East Java, South Kalimantan, and West Java.

Like other types of influenza, influenza viruses with this subclade start through droplets or splashes of saliva. In that way, this virus can be contagious when a person sneezes, coughs, or talks. In addition, contact or contact with virus-contaminated objects can also cause transmission.

The subclade K influenza A type A variant is indeed relatively new, so research on this disease is still ongoing. Its transmission is suspected to be easier than other types of influenza, but its severity has not been proven to be higher than other types.

Although it is still being studied, the symptoms that appear due to the spread of this variant are almost the same as other types of influenza A, namely high fever, chills, headache, nasal congestion, and sore throat.

However, in vulnerable groups such as children, the elderly, people with co-morbidities, and patients with immune disorders, this virus must still be watched out for.

"And if we delve further into this sublad K, it is a part or variant of the flu A H3N2, it cannot be detected clinically, which means that doctors, if they just look at it, cannot even distinguish whether it is influenza or not influenza, it is only possible to suspect it clinically similar to influenza," he said.

The most important preventive step is to strengthen individual health protocols and healthy living behaviors (PHBS). Nastiti appealed to the public to diligently wash their hands, eat nutritious food, exercise regularly, and wear masks in crowded places or when they feel unwell.

Meanwhile, the administration of influenza vaccine is also recommended as a medical protection effort to prevent transmission. Given that the influenza virus continues to mutate, the vaccine needs to be updated every year to adapt to the predicted variants of the virus that will circulate.

Influenza vaccination is mainly recommended for vulnerable groups such as children aged six months to five years, pregnant women, nurses, health workers, and people with chronic medical conditions.