Researchers found that risk was highest in summer, and that five airports account for more than 90 percent of the risk.
The five national quarantine stations are meant to ensure requirements for animal transportation in major localities along the north-south highway to prevent the spread of African swine fever.
The African swine fever virus was first detected in Vietnam in February and has spread to 29 provinces.
Six thousand pigs will be destroyed in Hong Kong after its first ever case of African swine fever was found in a slaughterhouse close to the Chinese border.
China has ordered mandatory testing for African swine fever at more than 10,000 slaughterhouses nationwide.
Animal feed ingredients might be pathways for introducing African swine fever virus into the US, but there is uncertainty because of the lack of data on transmission from these sources
The outbreaks were detected in the provinces of Gauteng and Mpumalanga.
African Swine Fever has swept across China with outbreaks in every province and all five autonomous regions. And experts believe there are far more cases than the 129 reported outbreaks.
Since August, African swine fever has wiped out pork production across China, Mongolia, Vietnam, and Cambodia, without signs of stopping.
The African swine fever epidemic in China poses a threat to the supply of the anticoagulant heparin which is made from pig intestines, and nearly 80 percent of those pig intestines come from China.