By Michael Le Page
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 disease 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.
Not a lot. There have been various media reports about the cases in Kerala but, so far, there appears to be only one published report of test results 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 whom the mother said had just had "tomato flu". A week after returning, the 13-month-old girl and 5-year-old brother developed a rash consisting of small fluid-filled blisters, with no other symptoms.
Julian Tang at the University of Leicester and colleagues found that the children were infected with a coxsackievirus, which is the cause of hand, foot and mouth disease, or HFMD. In other words, tomato flu could just be HFMD.
"Hand, foot and mouth has been around for centuries," Tang says. "I was bemused to see this media storm."
Doctors 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 as saying.
No, it's not. It is true that a letter published in The Lancet described it as "a new virus". However, this letter presented no evidence and has been criticised by some other experts.
"[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," tweeted Vinod Scaria 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, Tang says. 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 do not cause fluid-filled blisters, the symptom that led to the term tomato flu.
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.
That is not clear. However, there can be a lot of variation in the rashes caused by a single virus, Tang says. What's more, new enterovirus variants have emerged in China and spread around the world in recent decades. These newer lineages can manifest differently, he says. One, called coxsacksie A6, sometimes causes large blisters a centimetre or so across.
"It's very alarming for parents," Tang says. "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 twenty or thirty years ago."
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 been a surge of HFMD infections after children returned to school after covid restrictions ended.
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," Tang says. "Very few get severe disease, very few are left with scarring."