Explained: What is tomato flu — and the enterovirus that may be causing the outbreak

So, what is tomato flu?

Tomato flu or tomato fever is characterised by fever, joint pain, and red, tomato-like rashes usually seen in children below the age of five years. This is accompanied by other symptoms of viral fevers such as diarrhoea, dehydration, nausea and vomiting, and fatigue.

This was thought to be an after effect of dengue and chikungunya that is commonly seen in Kerala. However, researchers now believe that it is HFMD caused by enteroviruses like Coxsackievirus A-6 and A-16.

“Tomato flu could be an after-effect of chikungunya or dengue fever in children rather than a viral infection. It could also be a new variant of the viral hand, foot, and mouth disease, a common infectious disease targeting mostly children aged 1–5 years and immunocompromised adults,” the recent correspondence in The Lancet read.

Dr Ekta Gupta, professor of virology at the Institute of Liver and Biliary Sciences, said, “HFMD is not a new infection, we have read about it in our textbooks. It is reported from time to time across the country, but it is not very common.”

Why is tomato flu infection spreading now?

Dr Gupta said, “Perhaps there is more attention on the infection because more cases are being reported this year — this could either be because there actually are more cases or because we are more vigilant about viral infections and testing after Covid-19.”

She explained that since the disease is self-limiting, doctors do not usually test for it. “There are so many viral infections in children, but we cannot — and there is no need to — test for each and every one of it. However, we are now seeing more and more viral infections because testing for viral infections has increased over the last five years with virology labs being set up across the country. And the pandemic has given a further push to such surveillance,” Dr Gupta said.

While such surveillance is an important tool to keep an eye out for viruses in circulation in the community, it is not needed for individuals, Dr Gupta said. “For example, HFMD can easily be diagnosed by observing the symptoms, especially the red rashes.”

Another explanation for the infection picking up now is the re-opening of schools, said Dr Asawathyraj, scientist at Institute of Advanced Virology, who has been working with the infection.

Which pathogen is causing it now? And how is the clinical presentation different?

According to Dr Asawathyraj, who characterised the virus from Kerala and has been studying the infection, the current HFMD cases are mainly caused by Coxsackievirus A-6 and A-16. Another pathogen — Enterovirus71 — that also causes the disease is not very prevalent now, according to her.

This is good because the pathogen was known to lead to severe neurologic symptoms, including fatal encephalitis (brain inflammation).

“In almost all cases, say 99.9% cases, the disease is self-limiting. But, in a small number of cases it can lead to CNS (central nervous system) complications,” said Dr Asawathyraj.

She added that the disease this time around has some atypical presentation as well. The red “tomato” rashes were traditionally restricted to the mouth (tongue, gums, and inside of the cheek), palms, and soles. However, now doctors are also reporting rashes on the buttocks, and a shedding of nails.

Asked whether the rashes can be mistaken for monkeypox, for which states are on alert after an increased global spread, Dr Asawathyraj said that the rashes can be distinguished just by visual inspection.

“The monkeypox rashes are more deep rooted and the distribution is also different,” she said.

Is there a treatment for tomato flu?

There is no specific treatment or vaccine available for the disease. Those with the infection are treated symptomatically, such as prescription of paracetamol for fever.

How can tomato flu be prevented?

As it happens mainly in children, the Centre’s advisory to states that was issued on Tuesday focuses on preventions in these age groups.

As per the advisory, anyone suspected to have the infection should remain in isolation for five to seven days after the onset of the symptoms.

It states that children must be educated about the infection and asked not to hug or touch other children with fever or rashes. The children should be encouraged to maintain hygiene, stop thumb or finger sucking, and use a handkerchief for a running nose, the advisory states.

If a child develops symptoms, they should be isolated, their utensils, clothing, and bedding must be regularly sanitised, they must be kept hydrated, and the blisters must be cleaned using warm water, according to the advisory.

It also states that testing should be conducted to take measures if there is an outbreak. Any respiratory, faecal, or cerebrospinal fluid samples (in cases with encephalitis or inflammation of the brain) have to be collected within 48 hours of illness. The biopsy of the lesions or skin scraping samples does not have such time limits.