At a meeting with city officials Friday, Son urged that they speed up the process of mass testing to track down infections among the community to locate infected areas as soon as possible. For this, medical personnel should make effective use of the rapid test method, he said.

"The evolution of the epidemic is still unpredictable. In addition to the pool testing method (in which 10-15 different samples are pooled into one for testing and in case the pool tests positive, each one is tested separately later), the city’s health sector should reinforce its medical force for making the testing campaign as effective as possible," Son said.

So far, the city has used just 128,000 rapid test kits out of a total of 222,000.

Son advised the city to carry out the mass test program in different shifts to avoid gathering of big crowds that heighten infection risks. He suggested that, if possible, the tests should be done inside each residential area instead of having a lot of residents gather at the same time at some venue.

HCMC chairman Nguyen Thanh Phong said the Covid-19 wave Vietnam is experiencing is "more dangerous, complicated and unpredictable than previous ones."

Between June 19 and 30, every day the city has recorded 65 cases with unknown sources of transmission and around 35 ofthese were detected only after people visited hospitals seeking treatment for other health problems.

The spread of the disease has proved how complicated the pandemic has become, especially considering the World Health Organization warning that the Delta variant is much more transmissible and has the ability to reduce the effect of Covid-19 vaccines developed to date, said Phong.

"The rate of secondary infection and the spreading speed of this variant is strong, therefore the number of infections is likely to keep rising in the coming days," Phong said.

So far, in the ongoing wave that broke out over two months ago, HCMC has registered nearly 5,000 cases and is currently the second-worst hit among all 52 infected cities and provinces, following the northern province of Bac Giang.