The so-called tomato flu spreading among children in Kerala, India, is likely caused by hand-foot-and-mouth disease, a common childhood illness that is usually mild.
25 Aug 2022
In recent weeks, there have been reports of an illness called “tomato flu” affecting a small number of children in Kerala, India. It seems that tomato flu is simply a misleading new name for a common and usually mild childhood illness known as hand, foot and mouth disease. It is also possible that some of the cases are due to the mosquito-borne diseases chikungunya and dengue fever.
What do we know about tomato flu?
Not much. There have been several media reports about the cases in Kerala but, so far, there seems to be only a published report of test results of 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, according to the mother, 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 of the University of Leicester in the UK and colleagues found that the children were infected with a coxsackie virus, which is the cause of hand, foot and mouth disease (HFMD). In other words, tomato flu could just be HFMD.
“The hand, the foot and the mouth have been around for centuries,” says Tang. “I was surprised to see this media storm.”
Physicians in India have come to the same conclusion. “Tomato fever is a misleading colloquial name for hand, foot and mouth disease”, Rajeev Jayadevan of the Indian Medical Association is reported saying.
So it’s not a new virus after all?
“[It] seems to ignore the facts and the body of information already known about the disease, and even tries to paint an alarming picture and sensationalize the subject”, tweeted Vinod Scaria at the Institute of Genomics and Integrative Biology in India.
However, it is possible that some of the children in Kerala who reported having the tomato flu actually had dengue or chikungunya, says Tang. These mosquito-borne diseases cause skin rashes, fever and joint pain, and some children with tomato flu are said to have had these symptoms. However, dengue and chikungunya do not cause fluid-filled blisters, the symptom that led to the term tomato flu.
And it has nothing to do with the flu or tomatoes?
No. The coxsackieviruses that cause HFMD belong to a group of viruses called enteroviruses, which are not related to influenza viruses and have nothing to do with plants.
Why did some doctors in Kerala think it was a new disease?
That is not clear. However, there there can be a lot of variation in rashes caused by a single virus, says Tang. Furthermore, new variants of enteroviruses have emerged in China and spread throughout the world in recent decades. These new bloodlines can manifest differently, he says. One, called coxsackie A6, sometimes causes large blisters about a centimeter wide.
“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 evolving.”
“Unless you work in the field and follow it closely, you won’t notice this evolution of this disease and the rash moving away from the classic presentation that we saw 20 or 30 years ago,” he says.
That said, Tang was surprised to find that the virus in the two children in the UK was coxsackie A16, which is one of the oldest lineages. It is still one of the most common causes of HFMD.
Both the A6 and A16 circulate in India and there have reportedly been there has been a wave of HFMD infections after children returned to school after covid-19 restrictions ended.
Are there treatments for HFMD?
No, there are no treatments, but the vast majority of children recover quickly with no lasting effects. Some children develop serious complications, such as encephalitis (swelling of the brain) and acute flaccid paralysis (weakness of the arms or legs), but this is rare.
“The most important thing is that the children recover,” says Tang. “Very few develop serious illness, very few are left with scars.”
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