Reports on African swine fever on the Chinese mainland dropped significantly in the first quarter of the year compared to the same period in 2019, the agricultural authority revealed on Thursday.

As of March 19, the Ministry of Agriculture and Rural Affairs has received four reports on African swine fever this year, said Wei Hongyang, deputy director of the ministry's animal husbandry and veterinary bureau.

One case related to a wild boar while the other three cases all happened to captive bred hogs, said Wei at a news conference held by the State Council's Joint Prevention and Control Mechanism.

To date, a total of 324 hogs were disposed of due to the infection, a dramatic decline compared to the same period in 2019, according to Wei.

In the first quarter of last year, he revealed that the country had 13 reports on African swine fever and lost more than 197,000 hogs.

Wei said investigations have been conducted on the reports within the year and the result showed that most of the cases resulted from illegal transportation.

"None of those vehicles transferring the infected hogs had their information recorded in local departments as required. And the hogs had not received quarantine inspection," he said.

Of those cases, some were traded online, which makes inspection work from the agricultural department even harder, according to Wei.

Last week, the ministry sent a notice to agricultural departments at all levels, urging them to strengthen inspection work and prevent the situation from happening again.

African swine fever is believed to infect only pigs, and no humans or other species have thus far been infected.

China reported its first case of the disease in August 2018 in Northeast China's Liaoning province. Later outbreaks were reported in other provincial regions.

At the news conference, Wei said that the ministry has received applications on the clinical testing of vaccines for preventing African swine fever. "We will speed up the approval and maintain a high level of the vaccine's quality," he said.