A subvariant of COVID-19 is more contagious than the Omicron strain, sparking renewed concerns over a possible surge of cases in low vaccine areas.

BA.2, a subvariant dubbed “stealth Omicron,” was found to be at least 30% more transmissible than the original Omicron strain, according to the World Health Organization. The finding has caused concerns that the more transmissible subvariant could cause another wave of COVID-19 infections in communities with low vaccination rates.

“There are tens of millions of people who haven’t been vaccinated, a proportion of those haven’t been exposed to Omicron yet,” Dr. Peter Chin-Hong, a professor of medicine at the University of California San Francisco, told KPIX 5.

The professor also added that COVID-19 measures that worked in preventing an Omicron infection may not be as effective against the new subvariant.

The WHO’s findings echoed that of a Danish preprint study published in January showing unvaccinated people were 10% more likely to catch BA.2 and 20% more likely to pass it on.

In comparison, people who had been boosted against COVID-19 were 20% less likely to be infected than those who received two doses and 20% less likely to pass the virus to other people.

In addition to the new subvariant being more contagious, a preprint study published on Feb. 14 by researchers from Japan found that the BA.2 subvariant could cause more severe symptoms. However, health experts note that the study was done in hamsters.

It remains unclear how severe the Omicron subvariant could be. Data from South Africa and the United Kingdom showed that hospitalizations continue to decline even as the BA.2 variant spreads. However, hospitalization rates continue to soar in Denmark, where the “stealth Omicron” accounted for 60% of all COVID-19 cases, as of the second week of January.

As of Tuesday, the BA.2 subvariant is dominating in at least 10 countries -- Bangladesh, Brunei, China, Denmark, Guam, India, Montenegro, Nepal, Pakistan and the Philippines, WHO’s weekly epidemiological report showed.

In the United States, the BA.2 Omicron subvariant accounts for 3.8% of all new confirmed COVID-19 cases.

Globally, COVID-19 has infected 427,358,056 people and claimed 5,904,723 lives since the beginning of the pandemic, according to Johns Hopkins University data