The gene sequencing of the COVID-19 outbreak in Guangzhou, Guangdong province, indicates it is very similar in structure to the mutated strains detected in India, a senior health official from the city said on Sunday.

"And it has the characteristic of rapid spread," Chen Bin, deputy director of the city's health commission, said at a news conference in Guangzhou on Sunday.

She urged relevant departments and medical staff to act quickly to block the chain of infection and control the spread of the coronavirus in the southern metropolis.

Zhang Zhoubin, deputy director of the Guangzhou center for disease control and prevention, said the strain of coronavirus is highly transmissible.

"The virus can be transmitted through a meal or through a short period of indirect contact," he said.

The city reported five confirmed cases and 21 asymptomatic carriers as of 2 pm Sunday after the first confirmed case was detected in the city's Liwan district on May 21, Chen said.

To prevent the virus from spreading, the city government tightened its disease control and prevention measures over the weekend. Six communities and housing estates previously designated as low-risk areas were raised to medium-risk ones, Chen said.

In addition to asking local residents to get vaccinated, the city has organized nucleic acid testing in Haizhu and Yuexiu districts starting from Sunday. Residents in designated areas of Tianhe, Baiyun and Panyu districts have also been required to take nucleic acid tests to expand the screening of suspected patients and asymptomatic carriers.

Liwan previously required all its residents to take nucleic acid tests.

As of Saturday, more than 2.25 million residents of the city have had samples collected for nucleic acid tests, Chen said. More than 10,000 medical workers from the entire city have been sent to Liwan to help vaccinate locals against COVID-19 and collect samples for nucleic acid testing.

Deng Wenjun, director of circulation section with Guangzhou Supply and Marketing Cooperative said there are adequate supplies of food and daily necessities in the medium-risk areas.