Authorities in Hangzhou in the eastern Chinese province of Zhejiang were looking for visitors to an eye clinic on Wednesday after a student from Xinjiang in the country’s far west was found to be an asymptomatic Covid-19 patient. The 19-year-old student tested positive for both antibodies and the virus when he visited the clinic at the Second Affiliated Hospital of Zhejiang University school of medicine for a procedure on Tuesday. The patient showed no symptoms such as fever or cough. Eight close contacts of the students have been quarantined. Antibody and nucleic tests were conducted on the 463 clinic staff and all came back negative, according to the Hangzhou Centre for Disease Control and Prevention. The patient flew from Kashgar via Urumqi in the Xinjiang Uygur autonomous region on July 13 and the Hangzhou health authority concluded the case was imported from Xinjiang, which has been battling a new wave of Covid-19 cases since July 15 , when the first new infection in five months was reported. The region has reported 670 Covid-19 cases in less than a month, gradually rising from single digits and peaking on July 30 with 112 cases and then falling to dozens of new cases each day. It reported 22 new cases on Tuesday. The patients were an average 35 years old and, as such, their cases were mostly mild, according to Jiao Yahui, a senior official with the National Health Commission. Some patients were discharged after two weeks in hospital and 52 of the 670 cases since July have been discharged. Most of the cases were reported in the Xinjiang capital Urumqi, where the subway was stopped and residential areas were closed under a lockdown. Unlike other cities, Urumqi has not released epidemiological investigation results but Jiao suggested this was not necessary because, in addition to quarantining the close contacts of people who tested positive for the coronavirus, close contacts of those close contacts were also quarantined as a precaution. “Our epidemiological investigators and relevant personnel, such as information technology personnel, have used big data and large-scale nucleic acid tests to cover all personnel,” Jiao said on Wednesday morning. “We have expanded the epidemiological investigation to close contacts of the close contacts and all were under centralised medical observation under quarantine.” The health commission had sent a team of more than 400 staff from 12 provinces to help Urumqi carry out large-scale tests. They were now conducting 700,000 tests a day and so far had done about 6 million tests, she added. The source of the outbreak in Xinjiang is still unknown. The local health authority last month denied speculation that it was imported from neighbouring Kazakhstan and said the first known case in the region had no history of overseas travel. Cui Yan, director of the Xinjiang Centre for Disease Control and Prevention, said epidemiological investigations showed the cases were from the same source and genome sequencing of early cases indicated “the epidemic originated from the same source of infection”. Jiao said researchers were working on tracing the origin of the infection, including virus isolation and cultivation and genome sequencing.