Wearing masks and keeping their distance, Hong Kong pupils wait outside a school. Photo: cnsphoto

A nurse in Hong Kong tested positive for COVID-19 on Thursday, the Hong Kong government announced on the same day. The case was the city's latest infection from an unknown source following a few sporadic cases from unknown origins reported since Hong Kong was hit by a third wave of the epidemic in mid-July.

The most recent patient, a nurse working at Queen Elizabeth Hospital in Hong Kong's Kowloon area, tested positive for COVID-19 on Thursday morning after he saw a doctor on Wednesday due to a fever, according to a press release that the Hong Kong Special Administrative Region (HKSAR) government published on Thursday.

Epidemiological tracing showed the patient did not have any contact with any confirmed cases of COVID-19 in the past two weeks, said the press release, adding that no patients in the ward where he works are classified as close contacts.

The hospital has since conducted tests for the 44 patients and 29 medical personnel in the ward, all of which tested negative for COVID-19. It has also tracked six employees who had meals with the confirmed patient, showing no symptoms so far.

When and how the patient was infected by the virus seems to be a mystery as the preliminary investigation shows "there is no evidence suggesting he acquired the disease in the hospital," read the press release.

The pandemic situation in Hong Kong has largely improved with daily new confirmed local cases sharply decreasing from dozens in late July to near to zero in September. Regardless, sporadic cases from unknown sources have made people in the city worried, especially after some venues, including bars and pubs, started to reopen as Hong Kong further relaxed its social-distancing measures.

One resident, Cheung Ka-yan, 27, said she is feeling depressed as cases of unclear origins appear from time to time. "I'm worried and have no idea when this will come to an end," Cheung told the Global Times on Friday, saying she continues to wear masks and regularly washes her hands to avoid being infected.

Wang Guangfa, a respiratory expert at Peking University First Hospital, speculated that the cases from unknown sources may be linked to imported patients in Hong Kong.

"One possibility is that some imported cases have given rise to small-scale community transmissions that haven't caused much notice," Wang told the Global Times on Friday, urging Hong Kong - as an international city with people from all over the world coming in - to enhance its tracking and surveillance on imported patients, as the global pandemic situation remains serious, especially in the US, India and Europe.

Wang suggested that Hong Kong should find out the sources of these cases as soon as possible, considering the strong infectiousness and high mortality rate of the virus. "The fatality rate of COVID-19 on the Chinese mainland, except Hubei Province, is 0.6 percent, triple that of the flu," Wang said.