HONG KONG (BLOOMBERG) - Hong Kong's new coronavirus outbreak is proving more aggressive than its previous waves of infection, in a cautionary tale that the worst may be yet to come in the global pandemic.

Authorities reported 50 local virus cases on Friday, bringing total infections to over 350. The former British colony is now one of the first places in the region to see a new wave dwarf previous outbreaks.

The resurgence in the Asian financial hub has moved at an aggressive pace and erupted less than two weeks ago, after a long stretch during which residents returned to work and normal life. About a third of infections in the new outbreak are of unknown origins, signaling that hidden chains of transmission are widespread.

A similar scenario is building in Japan and Australia, reflecting the challenge of containing the pathogen even in places that were widely lauded and emulated for their containment strategies. The new waves are a sobering reminder to other regions further behind on the pandemic timeline, like Europe, on challenges to come.

Tokyo and Australia's Victoria both marked record single-day highs on Friday of 293 and 428 respectively.

"Countries which controlled the disease well in the early part of the year will remain at risk of outbreaks and even sustained community transmission, until we have a vaccine," said Raina MacIntyre, professor of global biosecurity at the University of New South Wales in Sydney.

"Whether or not the virus has mutated is speculation at this stage, but there is some evidence the dominant strain in the world is more transmissible than the initial strain in Wuhan," she said.

​However, the size of the new waves in the region may reflect more testing and earlier detection of cases, and officials are hopeful of minimising economic and social suffering with better management strategies.

Doctors now know better how to treat Covid-19, limiting the number of cases that deteriorate to intensive care or death. The healthcare systems in cities grappling with new outbreaks are not being overwhelmed, unlike in the worst-hit places like New York state and Italy during the first wave.

Still, without an effective and widely distributed vaccine, cities are likely to continue in a state of limbo in which easing of social distancing will lead to a spike of infection. The virus' ability to spread silently for weeks is still not fully understood by scientists, some of whom suspect that it can linger in the air for hours.