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In recent weeks, there have been reports of a disease dubbed “tomato flu” affecting a small number of children in Kerala, India. It appears that tomato flu is simply a new and misleading name for a common and usually mild childhood illness known as . It is also possible that some of the cases are due to the mosquito-borne diseases chikungunya and dengue.

What do we know about tomato flu?

Not a lot. There have been various media reports about the cases in Kerala but, so far, there appears to be from children with what appears to be tomato flu.

These two children had just returned to the UK from Kerala, where they had played with another child who the mother said had just had “tomato flu”. A week after returning, the 13-month-old girl and her 5-year-old brother developed a rash consisting of small fluid-filled blisters, with no other symptoms.

Julian Tang at the University of Leicester in the UK and his colleagues found that the children were infected with a coxsackievirus, which is the cause of (HFMD). In other words, tomato flu could just be HFMD.

“Hand, foot and mouth has been around for centuries,” says Tang. “I was bemused to see this media storm.”

Doctors in India have . “Tomato fever is a misleading colloquial name for hand, foot and mouth disease,” Rajeev Jayadevan of the Indian Medical Association .

So it isn’t a new virus after all?

No, it’s not. It is true that described it as “a new virus”. However, this letter presented no evidence and has .

“[It] seems to ignore the facts and the corpus of information already known for the disease, and even tries to paint an alarming picture and sensationalize the issue,” at the Institute of Genomics and Integrative Biology in India.

However, it is possible that some of the children in Kerala said to have had tomato flu really had either dengue or chikungunya, says Tang. These mosquito-borne diseases both cause rashes, fevers and joint pain, and some children with tomato flu are said to have had these symptoms. However, dengue and chikungunya don’t cause fluid-filled blisters, the symptom that led to the term tomato flu.

And it has nothing to do with flu or tomatoes?

No. The coxsackieviruses that cause HFMD belong to a group of viruses called enteroviruses, which aren’t related to influenza viruses and have nothing to do with plants.

Why did some doctors in Kerala think it was a new disease?

That isn’t clear. However, there caused by a single virus, says Tang. What’s more, new enterovirus variants have emerged in China and spread around the world in recent decades. These newer lineages , he says. One, called coxsackie A6, sometimes causes large blisters a centimetre or so across.

“It’s very alarming for parents,” says Tang. “Maybe some of the doctors in Kerala are not familiar with these new manifestations and have raised the alarm about something that is just evolving,”

“Unless you work in the field and follow it closely, you won’t be aware of this evolution of this illness and the rash away from the classic presentation we saw 20 or 30 years ago,” he says.

That said, Tang was surprised to find the virus in the two children in the UK was coxsackie A16, which is one of the older lineages. It is still one of the most common causes of HFMD.

Both A6 and A16 circulate in India, and there has reportedly after children returned to school after covid-19 restrictions ended.

Are there any treatments for HFMD?

No, there are no treatments but the vast majority of children recover quickly with no long-lasting effects. A few children develop serious complications such as encephalitis (brain inflammation) and acute flaccid paralysis (weakness of arms or legs), but this is rare.

“The most important thing is that the kids recover,” says Tang. “Very few get severe disease, very few are left with scarring.”