– Chinese pig farmers, already reeling from rising feed costs in Beijing's tariff fight with U.S. President Donald Trump, face a new blow from an outbreak of African swine fever that has sent an economic shock wave through the countryside.

First detected in August, the disease has killed 1 million pigs, prompting authorities to restrict shipments of most of China's 700 million swine, even though nearly all are still healthy. That has disrupted supplies of pork, China's staple meat, to big cities while prices collapsed in areas with an oversupply of pigs that farmers are barred from shipping to other provinces.

"I can only manage to break even at the current price," said a breeder on the outskirts of Shenyang, northeast of Beijing, where the first case was reported Aug. 3. She said she was rearing about 100 pigs and would give only her surname, Yan.

"Unless we see a higher price for pigs, all my work this year would have gone for nothing," Yan said.

African swine fever doesn't affect humans but is highly contagious in pigs, making it a serious threat to farm areas.

On Friday, the first cases were reported in Beijing, the capital. Authorities said a total of 86 pigs at two farms in suburban Fangshan district died.

Also Friday, Xiamen Airlines, a midsize Chinese carrier, announced it was suspending use of pork in in-flight meals.

The outbreak adds to a swarm of challenges for Chinese leaders as they grapple with Trump over Beijing's technology policy and try to shore up cooling growth in the world's second-largest economy.

"Farmers have been losing money in pig-breeding provinces for the past couple of months and their confidence has been shattered," said Feng Yonghui, chief analyst of soozhu.com, a pork consultant.

The cost of raising pigs spiked after Beijing retaliated for Trump's tariff hikes on Chinese goods by slapping 25 percent duties on imported U.S. soybeans used as animal feed.

American farmers supplied about one-third of China's imports of 96 million tons of soybeans last year, while its own farms produce about 15 million tons a year.

Soy prices have risen by as much as 4 and 5 percent per month since then in some areas. Importers are buying more soy from Brazil and Argentina, the other major exporters. Authorities have encouraged breeders to look at other protein sources such as canola.

Since the first swine fever case in August, sick animals have been found in areas from Jilin province in the northeast to Yunnan on China's southern border with Vietnam.

Authorities responded by banning shipments of all pigs from any province with one case.

Authorities have found 73 outbreaks in domestic pigs and one infected wild boar in 47 cities in 20 provinces, according to an Agriculture Ministry official, Feng Zhongwu.

"The task of prevention and control is still very arduous and the work is extremely urgent," Feng said at a news conference Friday.

It wasn't clear how the virus reached China but it was found to be genetically similar to versions in Russia, Poland and Georgia, said another official, Huang Bao.