Japanese health authorities are concerned that variants of the coronavirus are driving a nascent fourth wave in the pandemic with just 109 days remaining until the Tokyo Olympics, according to Reuters.

The variants appear to be more infectious and may be resistant to vaccines, which are still not widely available in Japan. The situation is worst in Osaka, where infections hit fresh records last week, prompting the regional government to start targeted lockdown measures for one month.

A mutant Covid-19 variant first discovered in Britain has taken hold in the Osaka region, spreading faster and filling up hospital beds with more serious cases than the original virus, according to Koji Wada, a government adviser on the pandemic.

“The fourth wave is going to be larger,” said Wada, a professor at Tokyo's International University of Health and Welfare. “We need to start to discuss how we could utilise these targeted measures for the Tokyo area.”