The outbreak was first reported on 6th May 2022 (1).

First cases of the current outbreak were identified in the Kollam district of Kerala, India (1).

India’s Ministry of Health and Family Welfare recently suggested that Tomato Flu/Fever may be caused by Coxsackieviruses (a group of Enteroviruses), which also cause hand, foot and mouth disease (HFMD) (2, 3). Doctors in Kerala support this, stating that Tomato Flu/Fever is a variant of HFMD and has been observed in children in India as far back as 2001 (4). Historically, Tomato Flu/Fever has been the colloquial term provided to the unusual blisters observed in some HFMD cases.

Reported cases in the current outbreak have been documented since May 6th, 2022 (1).

Ongoing as of 1st September 2022.

India is so far the only country in the world with reported cases of this disease. The regions in India that have been affected include Haryana, Odisha, Kerala and Tamil Nadu (5, 6).

Two cases of possible Tomato Flu/Fever were reported in the United Kingdom, where a 13-month-old girl and her 5-year-old brother returned from a family holiday in Kerala and presented with rashes on their hands and legs (7). Both children tested positive for Enterovirus (EV) and sequencing confirmed it was caused by Coxsackie A16, one of the most common EV causes of HFMD in India (7).

In the current outbreak, more than 100 cases have been reported as of 26th July 2022 (1, 8, 9).

Clinical signs typically appear in children. These include (1) :

• Red, painful enlarged blisters (tomato like)
• Rashes
• High fever
• Swelling of joints
• Body aches
• Fatigue
• Nausea
• Vomiting
• Diarrhoea
• Fever
• Dehydration

The primary mode of transmission for HFMD virus (HFMDv) is via faeces, respiratory droplets, or through fluid from blisters or scabs (2, 10). Transmission can occur through direct contact, such as touching an infected person, or indirect contact, such as touching surfaces (2). HFMD is highly contagious (11).

Tomato Flu/Fever presents in children younger than 5 years of age (4), which is typical of HFMD (1). Some cases have been reported in children aged up to 9 years old for Tomato Flu/Fever (12).

India has not recorded a death attributable to Tomato Flu/Fever (CFR: 0%) (4).

No complications of HFMD or Tomato Flu/Fever have been reported in India to date. One of the largest outbreaks of HFMD in Singapore (30,000 cases) reported major complications of infection such as paralysis, pulmonary oedema and neurological disorders (4). Additionally, if the virus spreads to vulnerable populations such as the elderly and immunocompromised persons, this could result in significant complications. The unusual presence of the tomato-like blisters, which are typically larger in size than the clinical manifestations of typical HFMD, is something to be considered.

No vaccine exists to prevent Tomato Flu/Fever. Recommended means of prevention involve practicing proper hygiene and sanitation (1, 2, 12).

Currently, no antiviral drugs exist to treat Tomato Flu/Fever. Isolation is recommended for 5 to 7 days from when symptoms present themselves, in order to manage the disease (12). Children are mostly treated with anti-allergic medicines and ointments (13).

The current outbreak in India was first recorded in the EPIWATCH system on May 2nd, 2022, in an article reporting an outbreak of Tomato Flu/Fever, also referred to as HFMD, in the district of Wayanad in Kerala, India (14, 15). On 10th May, 82 cases were reported in the Kollam area (16), with cases also reported in the bordering area of Tamil Nadu, although no case numbers were reported in this outbreak (17). The outbreak spread to Odisha, where a further 26 cases (referred to as both Tomato Flu/Fever and HFMD) were reported on the 25th of May 2022 (18). There have been no further cases reported, however due to correspondence published online in The Lancet on 17th August 2022 (1), there has been an increased interest in “Tomato Flu/Fever” (Figure 1).

The Health Ministry of India has responded with the issuing of an advisory on Tomato Flu/Fever – which they confirm is the colloquial term for HFMD – to note the symptoms and be aware that it is highly contagious among school aged children (19). The advisory states that the name “Tomato Flu/Fever” comes from the symptoms of small red round blisters that “resemble tomatoes when they enlarge” (19). Genotyping was performed in swabs of blisters in two children suffering tomato fever who recently returned to the United Kingdom from Kerala, India (7). The results showed evidence of infection with enterovirus (EV) by PCR assay, and genotyping showed a Coxsackie A16 infection, which is a known cause of HFMD (7).

A previously documented outbreak of “Tomato Flu/Fever” in 2007 in the same state of India, Kerala, affected approximately 2,800 people (20). The symptoms included fluid-filled “tomato-like wounds”, especially on the hands and legs (20). At the time, this was assumed to be a complication of a recent infection with Chikungunya, due to a large epidemic the previous month in the same region (7, 20). However, this was not confirmed.

In 2008, an epidemic of Chikungunya occurred in the coastal region of the state of Karnataka, just north of Kerala (21). A total of 39,042 suspected cases were recorded by the local health authorities, and a study was done on the mucocutaneous presentations of Chikungunya in a proportion of these cases (21). A generalized maculopapular rash was found to be the most common, and the authors found that due to the intense erythema, the local population called the rash “Tomato Flu/Fever” (21). Even though cutaneous presentations of Chikungunya have been reported, such as the maculopapular rash and apthae-like ulcers, the pathogenesis of these symptoms is unknown (21).

Symptoms of Tomato Flu/Fever include fever, fatigue and body ache together with a rash. The rash is unusual in that the HFMD virus causes red and painful blisters throughout the body that can gradually enlarge to the size of a tomato, which are red in colour (1).

Some controversy exists on this ‘new’ illness. In a recent report published in August 2022, it was claimed to be a new viral “flu” that emerged in May 2022 over a period of 2 weeks in areas in the south of India: Kerala, Haryana, Karnataka, Tamil Nadu and Odisha (23). Interesting to note that HFMD is one of the diseases under surveillance by the Kerala State Health department (sporadic appearance in the period 2011- 2021 for which reporting is available) and on 8th May 2022, the Kollam district of India issued a health alert for HFMD (22).

The terms “Tomato Flu” or “Tomato Fever” are colloquial terms based on the characteristic red, “tomato”-shaped blister that appears on different parts of the body, which begin small and increase in size as disease progresses.

HFMD is a common febrile rash illness in children, caused by enteroviruses Coxsackie A16 (CA16), EV A71, Coxsackie A6, Coxsackie B and Echo viruses (24). Recent media reports from the Indian state of Kerala have highlighted cases of “Tomato Flu/Fever” in young children described as a febrile rash illness with round, red skin lesions looking similar to tomatoes (25). In a case report, the CA16 sequence, one of the most common enteroviruses causes of HFMD in India was identified in 2 children from the same household that developed the rash after returning from travel to India to the UK (7). Currently, there has been a push from experts to move away from the misleading name attributed to the illness (26). Local healthcare workers have been encouraged to address the disease as a variant of HFMDv and not stir up unnecessary panic on the emergence of a “new outbreak” which could just be a result of inaccurate terminology, as these reports of Tomato Flu/Fever emerged in a published article at the same time as a HFMD alert was issued in Kollam in May 2022, for the same cases.

In addition, the effects of the ongoing COVID-19 pandemic should not be overlooked. Besides the typical symptoms, there have been increasing reports of skin lesions being observed in those positive for COVID-19 or suspected cases globally (27-30). During the last two years, schools in India had been closed due to the COVID-19 pandemic and HFMD being a highly infectious disease, had less scope to spread among the larger paediatric population. The rise in cases this year could be attributed to re-opening of the schools and possibly a different, more infectious strain. With the circulation of other viruses, inadequate testing and poor-quality surveillance in a low resource setting, where healthcare systems are already burdened with ongoing monkeypox outbreak and COVID-19 pandemic, the use of colloquial terms may cause unnecessary panic in the current hypervigilant climate.

1. Is the unusual presentation of the enlarged ‘tomato’ like blisters in this outbreak due to a new variant of HFMDv or is this presentation seen in immunocompromised children, or those who have recently been exposed to COVID-19?
2. Could the colloquial terms ‘Tomato Flu’ or 'Tomato Fever' be misleading and confusing and therefore affect treatment if HFMDv cause is not suspected or clinically determined?
3. The term Tomato Flu/Fever is used to describe multiple diseases. Has there been diagnostic confirmation from India that this is not a mixed outbreak?
4. Can hypervigilance in the aftermath of the COVID-19 pandemic together with heightened media and journal interest can cause fear and panic in the population?