Tomato flu first drew the attention of clinicians in the Kollam district of Kerala, India, on 6th May 2022. Since then, hundreds of children have been affected, mostly under the age of nine. The causative agent for this outbreak was unknown at the time, but symptoms in children were found similar to those of chikungunya virus, including unusual tomato-shaped red rashes and blisters, and hence, it was dubbed as tomato flu.

Some experts believe it may be an after-effect of chikungunya or dengue fever, rather than a new viral infection. According to a letter published in the journal The Lancet Respiratory Medicine, fever, rashes and joint pains were the main symptoms among tomato flu-affected children. Tomato-shaped red rashes and painful blisters appeared on the skin, leading to skin irritations in children. Moreover, nausea, vomiting, fatigue and influenza-like symptoms were also observed during their illness.

In Nepal, a 45-year-old man with no travel history to India did not initially show symptoms, except joint pain. However, he soon developed tomato-shaped red rashes and blisters, especially on his palms, feet and tongue, approximately two weeks after being diagnosed with the dengue virus infection. Moreover, the patient complained of irritating, but painless rashes and blisters. The attending dermatologist ruled out other viral infections such as HIV (1 & 2), hepatitis viruses B and C, chicken pox, and herpes after laboratory testing and clinical examinations, respectively. This was the first reported case of tomato flu-like illness in Nepal, the second country after India.

Contrary to the outbreak seen among children below nine years in India, the patient who developed the illness in Nepal was an adult with different symptoms. The reason behind the different symptoms observed in India and Nepal is currently unknown. But age factor can be one possible explanation.

Initially, a new viral infection was believed to be responsible for the Kollam outbreak in India. However, tomato flu immediately became a debatable name among experts until the causative agent got identified. A recent letter published in The Pediatric Infectious Disease Journal reported that the causative agent of tomato flu was identified as an enterovirus (CA16) in two children, who had recently returned to the UK from Kerala, which is considered the most common cause of hand, foot and mouth disease (HFMD). HFMD is not a new disease. It has previously been reported in infants and children. It shows that due to a lack of molecular laboratory testing facility, it can cause a diagnostic delay that ultimately leads to inappropriate management and creates challenges in preventing its spread/outbreak, promptly.

In Nepal, several public and private molecular laboratories (PCR technique) were set up after the introduction of the SARS-CoV-2 virus, the causative agent of the Covid-19 pandemic.

According to The Lancet Respiratory Medicine journal, the authors were unsure about the causative agent of the tomato flu outbreak in the Kollam district. Despite this uncertainty, the authors recommended treating this disease symptomatically, including rest, plenty of fluids, and a hot water sponge to relieve irritation and rashes, assuming it might be a viral infection similar to that of chikungunya, dengue or HFMD. In fact, HFMD is a self-limiting infectious disease; hence, most people do not require specific treatment/medicine and get better within seven to 10 days. Severe complications such as meningitis, encephalitis or paralysis are possible, but extremely rare. No death was reported during the “Kollam tomato flu” outbreak. As per The Pediatric Infectious Disease Journal, the lesions virtually disappeared with no scarring in two children with tomato flu infection on days 6 and 16. As reported by our patient, his tomato-shaped red rashes and blisters began to heal on their own after a week.

HFMD is considered a highly contagious viral infection, especially during the first week of the illness, and is thus easily transmitted through an infected person’s respiratory droplets containing the virus during coughing or sneezing, as well as contaminated surfaces or objects, blister fluid and faeces. However, our patient denied any contact with sick people having similar symptoms to tomato flu. Despite the close contact with family members and sharing household objects, none of his family members got infected or developed symptoms similar to tomato flu.

In a letter published in the Pediatric Infectious Disease Journal, the authors, however, did not mention the spread of this virus among the family members (i.e. family history) after two children with tomato flu were diagnosed with an enterovirus (CA16) that causes hand, foot and mouth disease (HFMD). The transmission of this virus, therefore, seems obscure. Some experts have pointed out that the current tomato flu outbreak is a result of a new variant of HFMD. Thus, its presenting symptoms, route of transmission, and disease severity may differ from its original HFMD due to genetic variation, but it requires further study to refute or support this assumption. It is worth noting here that three Covid-19 waves with different variants of SARS-CoV-2 observed in Nepal resulted in different outcomes in terms of its symptoms, affecting age groups and disease severity and/or deaths.

For the first time, Nepal observed tomato flu-like illness in an adult followed by dengue fever. It raises several interesting but critical questions, such as: Was it a sequela of dengue fever or expanded dengue syndrome? Is the dengue virus capable of triggering hand, foot and mouth disease (HFMD)? Is a new variant of HFMD emerging? Such questions are still unanswered at the moment.