The World Health Organization has warned that Covid-19 is now being spread mainly by people in their 20s, 30s and 40s who may be unaware they are infected, potentially transmitting the disease to more vulnerable groups.

In a virtual briefing, the WHO’s western Pacific regional director, Dr Takeshi Kasai, said:

The epidemic is changing … People in their 20s, 30s and 40s are increasingly driving the spread. Many are unaware they are infected. This increases the risk of spillovers to the more vulnerable.

Surges have been reported in countries that appeared to have the virus under control, including Vietnam, which until recently went three months without domestic transmission due to its aggressive mitigation efforts, Reuters reported.

“What we are observing is not simply a resurgence. We believe it’s a signal that we have entered a new phase of pandemic in the Asia-Pacific,” Kasai said.