The reason is as follows: 1, the transmission of the virus needs a medium, brief airborne, human contact and attachment to body fluids, feces is the normal way of virus transmission. 2, courier distance, leaving the body fluids of the virus can not survive for a long time, more unable to replicate and infection, the main mode of transmission of the new coronavirus is droplet transmission. Virus survival time in the air at different temperatures and humidity is different, the higher the temperature, the more difficult it is for the virus to survive, the virus can be inactivated by heating at 56 degrees Celsius for 30 minutes, the virus will soon lose its infectivity at room temperature of about 25 degrees Celsius, but now it is winter, so the virus will survive longer in vitro. Unlike bacteria, viruses are usually more likely to spread in dry air, but this does not mean that they survive longer in dry air. Viruses are more likely to fall on the surface of objects and on the ground in moist air, and more likely to float in the air in dry air. Therefore, the virus is more likely to survive in the humid air. The current influenza A (H1N1) virus can survive in the air for two hours, which is the longest known survival time of the virus studied, the survival time of the coronavirus is similar to the influenza virus. 3, raw meat products and other food easy to provide host for the virus, easy to spread the virus, it is best not to use courier transport.