Why positive cases keep popping up in locked down communities
Residents pick up online orders and group purchased products at a local community within the precautionary area.
The time-lapse for screening data, family transmission and product delivery logistics are the main reasons for the rising number of local COVID-19 cases, even after Shanghai's lockdown and other control measures.
Shanghai has imposed its phased lockdown and follow-up control measures since March 28 when residents were asked to stay at home in most local communities.
However, the city has been reporting 20,000-plus daily new cases for almost a week.
Wu Huanyu, deputy director of the Shanghai Center for Disease Control and Prevention, said they've analyzed the situation in response to many citizens' questions and found several key reasons.
Firstly, the reported numbers are actually delayed due to the complicated testing process following the large scale of nucleic acid sample collection.
If a mixed sample tested positive, everyone must be retested individually, followed by epidemiological investigations on the confirmed cases, Wu said.
Secondly, the cross infection among family members has now become a key route of transmission. The highly contagious and concealing Omicron BA.2 sub-variant has an incubation period of three to five days. Once a family member tested positive, others were likely to have been infected but will test positive after the incubation period.
Thirdly, products and daily supplies are being transported across the city though residents are asked to stay at home. There are possibilities that products contaminated by the virus could cause infection after being touched.
Fu Chen, another deputy director of the center, asked citizens to avoid contact with volunteers or delivery staff when receiving group buying products or online orders.
They must wear a mask and glove when taking the parcels. They are asked to disinfect the surface of the box with alcohol wipes or mist spray and open after putting them aside for about half an hour. They should avoid taking the paper boxes or wrappings home.
Vegetables, fruits and other fresh food can be washed with flowing water or soaked in water for a while before being stored, Fu said.
