In a first, scientists identify variant of chickenpox-causing virus: ICMR-NIV study

The new study published recently in the recent issue of Annals of Medicine journal has reported the circulation of VZV clade 9 in India. So far the clade 9 is the most common strain in circulation in countries such as Germany, UK and USA. “As part of our surveillance for monkeypox cases, we encountered cases of VZV in the suspected Mpox cases among children and adults,” said Dr Pragya Yadav, senior scientist with ICMR-NIV, and one of the study authors.

“Our study hence focused on the genome characterisation of VZV in India,” Yadav said, pointing out that despite the infection with VZV clade 9 strain, there were no significant indications of heightened disease severity in the patients.

In rare cases, VZV infections can progress to the central nervous system involvement and severe complications. “It is critical to distinguish chickenpox from measles, bacterial skin infections, scabies, syphilis, medication–associated allergies, and Mpox viral disease,” study researchers said.

Mpox disease symptoms are frequently mistaken for VZV, as their clinical presentations often closely resemble each other. Hence there is a need for clinical differentiation between Mpox and VZV for accurate diagnosis. Recently, a multicentric Mpox outbreak was reported across 110 countries, with a total of 86,500 cases and 111 deaths till March 16 this year, including 22 cases and 1 death from India.

While the multi-country Mpox outbreak across the globe had led to the systematic surveillance of these cases in India, at ICMR-NIV a total of 331 Mpox suspected cases were tested for VZV through real-time PCR and of these 28 cases with vesicular rashes were found to be positive for VZV.

The incubation period of Mpox ranges from 5 to 21?days whereas, in the case of chickenpox, it is from 10 to 21?days. The evolution of rashes occurs quite slowly over a few days in Mpox but this occurs rapidly in chickenpox,” researchers said.

The current scenario of the Mpox outbreak, waning population immunity to orthopoxviruses, and non-inclusion of chickenpox vaccination in the national immunisation programme emphasise more on the laboratory diagnosis and identification of different clades of circulating VZV in India, according to the study.

Although clades 1 and 5 have been reported earlier, the circulation of clade 9 of VZV has been determined for the first time in India,” researchers said.

While there was no major indication of heightened disease severity, these recombinant patterns have led researchers to make a strong case for disease monitoring and surveillance of VZV infections in the country.

In a study of patients with central nervous system (CNS) involvement in VZV infection from the metropolitan region of New York City, the clade 9 strains were found in areas with a higher concentration of immigrants of Middle Eastern and Indian ethnicity, indicating the presence of clade 9 circulation in India.

In this study, two sequences from India belonged to clade 1 which were considered to be European and North American strains.

Clades 1 to 5 are most prevalent in the world, with clade 1 and 3 circulating in Oceania, Europe and America while clade 2 in Asia and clade 4–5 in South Asia and Africa. Most VZV infections observed in USA belong to clade 1 and 3.

However, with the introduction of varicella vaccine and changes in current immigration patterns, the current distribution of clades and relative involvement of each clade in CNS and non-CNS diseases is still unknown and opens the arena for research, researchers said.