(Yicai Global) Jan. 18 -- After it was confirmed that a person with Covid-19 in Beijing had recently sent and received international mail, China has been sterilizing incoming mail and parcels to prevent the transmission of coronavirus from overseas.

But international mail is still a potential contamination risk, said Zhang Liubo, chief expert on disinfection at the Chinese Center for Disease Control and Prevention. Yicai Global spoke with Zhang.

Yicai Global: Is there a risk of coronavirus transmission from international deliveries? Can the virus survive for seven days on such items?

Zhang: Covid-19 is still a global pandemic, so items sent from overseas could be contaminated. If the amount of the SARS-CoV-2 virus is relatively large, accompanied by organic matter like saliva, and there are low temperatures in storage and transportation -- especially amid the cold winter in the northern hemisphere, and cargo rooms in air freighters are also cold -- this creates a good environment for the virus to potentially survive for seven days or more.

The virus contaminates not only packaging, but also goods that people have touched. Express delivery staff did not get infected this time, which shows their protection and disinfection measures are working. We need to pay close attention to the risk of transmission from package deliveries.

YG: How do we currently disinfect imported items?

Zhang: We have regulations for disinfection in every link before letting imported items enter the market. China requires that packages should be disinfected where they are opened. We sterilize large packages outside after they come out from containers, middle packages when putting them into cold storage, and small parcels when they arrive at malls.

YG: Why are many items still testing positive for the coronavirus even though China has tightened up on disinfection of imported items?

Zhang: There are two main reasons. One is that the disinfection may not have been properly carried out, and the other is that personal protection by the contacts involved may have been insufficient.

There are disinfection technologies and processes for general items, but we did not require disinfection for frozen food in the past. These systems can achieve disinfection at low temperatures, but people sometimes do not use them properly. Also, some individuals get infected while disinfecting items, due to insufficient protection.

YG: Are items contagious when they test positive for the coronavirus?

Zhang: Not all items that test positive for the coronavirus are contagious. People can be infected only when the virus is active.

There has been fruit that tested positive for the coronavirus in China. A positive test result only means that the fruit has been infected. Some fruit, despite positive test results does not have any live virus. Fruit has a lower risk than frozen food, as international shipping of fruit does not require a cold-storage environment and generally takes a long time.

There is a fairly low risk of finding live coronavirus on fruit given the lengthy shipping process, even if their surfaces are contaminated.

The coronavirus can survive for a long time at low temperatures. Cold chain items provide a low temperature environment for the virus, allowing long-distance transmission and then potential Covid-19 cases. China has had several such cases.

Editor: Tom Litting