Of these, 15,000 were killed by the virus. The other 5,000 were destroyed as a precaution.
"It started with a few pigs a day, then it was hundreds," said Sun, a pig farmer and agricultural entrepreneur from Hebei Province, China. "In the end, 800 pigs would die in a single day."
African swine fever (ASF) is decimating China's pork industry, by far the largest in the world. The Dutch bank Rabobank, which lends to the global agricultural sector, estimates that the country's pig population could shrink by a third in 2019 due to a combination of illness and culling – up to 200 million animals.
that's almost as many pigs as in the US and Europe together.
The virus is harmless to humans but fatal to pigs – and so far there is no cure or vaccine. Outbreaks originating in Africa were registered in Eastern Europe and Russia before they first appeared in China last August.
Since then, it has expanded to other Asian countries, including Vietnam and Cambodia.
In March, the Chinese government announced it had done a "good check" on the epidemic. At a press conference last month, Beijing said that ASF is not spreading as fast as before.
China's central authorities have taken the right steps to bring the virus under control, according to the United Nations Food and Agriculture Organization (FAO).
"They did everything they could to control the disease, they had a plan, they had a strategy, they reacted very vigorously," said Vincent Martin, FAO representative in China.
farms wiped out
The extent of the outbreak, however, may be higher than assumed by official estimates because some farmers tell CNN that the disease is not always recognized locally.  Sun said first tests by provincial officials on his Hebei farm were negative for ASF. However, after putting pictures of the dead animals online, the country's Disease Prevention and Control Center tested them and confirmed that they carried the virus.
Also in Hebei, farmer Zhang Haixia watched as all her 600 pigs died. The official cause of death is a normal swine flu.
"Local officials were afraid to be held accountable," she told CNN. "They threatened us that there would be consequences if we contacted senior government officials who are afraid to lose their jobs."
CNN has asked the authorities in Hebei for an opinion, but received no response.
Martin of the FAO warned that it could take years for the outbreak to be completely contained.
"I'm not sure if we can say it's under control because we know how complex the disease is," he said. "We have experience in other countries where it took years to get these diseases under control."
Not enough pork in the world
One of China's main problems with curbing ASF is the pig industry is fragmented. According to Martin, there are thousands of small businesses that may not have the right biosafety measures to stem the spread of the disease.
Another complication is that the virus survives in pork products for months and thus can be reintroduced by chance.
And it is not only the producers who are injured. The epidemic could also have a wider economic impact: China is the world's largest consumer of pork, a staple food for the vast majority of its 1.4 billion people.
According to government forecasts, the pork price could rise to a record level in the second half of 2019 as demand overstretches supply.
Analysts say there are not enough pork in the world to meet China's expected shortage and consumers are likely to turn to other meat as a substitute.
Rabobank's report predicts an "unprecedented" shift in global protein supply to China to fill the gap.
Pork producers in Europe and the US are already beginning to increase their deliveries to China, although US exports have a duty rate of 62%. b Reason for the trade battle with China.
In the lunar calendar, 2019 is the year of the pig. It should be a auspicious year. For the Chinese pork industry it is anything but.