Shanghai designated its first high-risk area for COVID-19 along with two medium-risk areas on Sunday after a community infection was reported.

The new risk areas in Putuo and Baoshan districts were rated under China's newly-updated COVID-19 control protocol, which defines the living and working places of COVID-19 positive cases as high-risk areas, while some places they had been to as medium-risk, explained Zhao Dandan, deputy director of the Shanghai Health Commission.

Previously, the neighborhoods or workplaces of COVID-19 infections were mostly designated as medium-risk areas.

Shanghai currently has a high-risk area and four medium-risk areas in Putuo, Baoshan, Jing'an and Fengxian districts.

The city's latest infection, an asymptomatic case, is a 37-year-old woman living in Changfeng Community Subdistrict of Putuo. She tested abnormal during a regular nucleic acid, or polymerase chain reaction (PCR), test. The patient has taken the full two courses of COVID-19 vaccines.

About 100 close contacts have been put under quarantine and 40 of them have tested negative, Zhao said. More than 2,300 related personnel are undergoing PCR screening. Four environmental samples collected from the patient's home tested positive.

The neighborhood of 2077 Guangfu Road W. that the woman lives in thus became a high-risk area, while a teahouse in Caoyang Community of Putuo and a barbeque restaurant in Gaojing Town of Baoshan, where she had been to in the last two weeks, were elevated to medium-risk areas.

Wang Jue, deputy director of Putuo, revealed that the newly designated high-risk area has 20 high- and middle-school students who will soon take part in the gaokao, or the national college entrance examinations and the high school entrance examinations.

"The district government will arrange vehicles to take the examinees to quarantined exam sites and bring them home in a closed-loop management," Wang said.

Other sites in Changfeng and Caoyang subdistricts as well as Gaojing Town have become low-risk areas, Zhao added.

Under the 9th edition of the protocol, residents in high-risk areas, which are usually communities or villages, must undergo a weeklong home quarantine with frequent PCR tests.

The high-risk areas will be downgraded if there is no new infection in the past week and everyone tests negative on the last day of the lockdown.

People in medium-risk areas are only allowed to move around within the areas, which will be downgraded if no additional cases are detected for a week.

Residents in low-risk areas, or subdisticts and towns having medium- or high-risk areas, must have a 48-hour PCR test report to leave Shanghai.

Those coming or traveling from other domestic low-risk areas must take two PCR tests within three days after arriving in Shanghai, Zhao said.

Shanghai has reported zero community infections for almost a week after the city emerged from its long lockdown following the COVID-19 resurgence in early March.

"We must pay close attention to the new community case as Shanghai has fully restored its life and production orders," Zhao noted, pointing out that the risk of resurgence always exists and slackening off is not allowed.

The city reported two locally transmitted COVID-19 cases on Saturday. They are staff members serving inbound international flights at Pudong International Airport. They tested positive during a routine screening in central quarantine.

The duo was infected after being exposed to an environment contaminated by viruses from overseas, according to epidemiological investigation and gene sequencing, Zhao observed.