Molecular epidemiology of hand, foot, and mouth disease in Karnataka, India in 2022.

Background: Hand, foot, and mouth disease (HFMD) is an enteroviral disease that occurs as outbreaks and sporadic cases in India. In this study, we investigated and characterized the aetiology of HFMD cases that occurred in Karnataka, South India from April to October 2022.

Methods: Throat swabs, vesicular swabs, urine, and blood samples from suspected cases were analysed by reverse transcription polymerase chain reaction (RT-PCR) for the detection of enteroviruses. Molecular typing of the enterovirus-positive samples was carried out by amplifying the partial virion protein 1(VP1) gene sequence, followed by sequencing and phylogenetic analysis.

Results: Out of the 187 samples received from 82 cases, 93 (50%) tested positive (55/82 cases, 67%) for enteroviruses, with the majority of the HFMD cases reported in paediatric population of less than 5 years (36/55, 65.4%), while 3 cases (3/55, 5.4%) were adults. Out of the 55 enterovirus-positive cases, 31 showed partial VP1 region amplification and 19 of these cases were typed as coxsackievirus A16 (CV-A16) (13/19, 68.4%) and CV-A6 (6/19, 31.6%). The CV-A16 strains identified belonged to subclade B1c while two CV-A6 strains belonged to subclade E2. On molecular testing for other viruses causing fever-rash symptoms, 4/27 (15%) enterovirus-negative cases were detected as herpes simplex virus (1 case) and varicella zoster virus (3 cases) positive.

Conclusion: The main causative agent of HFMD in Karnataka in 2022 was CV-A16, followed by CV-A6. Apart from the common paediatric HFMD cases, adult cases were also reported during this period. Further studies involving laboratory and clinical investigations are essential for monitoring and managing HFMD in the community.