Most infected animals die within 10 days, according to the European Food Safety Authority. | Craig Lassig/EPA-EFE African swine fever: Everything you need to know An incurable pig disease is threatening Europe’s heavyweight pork industry.

Belgium's discovery of two cases of African swine fever raises the prospect of a nightmare scenario for big farms in the EU's agricultural heartlands.

Since 2014, the disease has been largely confined to the Continent's east. The Belgian cases bring the hemorrhagic fever within striking distance of major piggeries in Germany, France and Denmark.

Europe produces 20 percent of the world's pork and has deep fears about whether global trading partners could react with a blanket ban against the EU, as Russia did in 2014.

Here's what you should know about the disease.

1) What is African swine fever?

It is brutal. First emerging in Kenya early in the 20th century, the worst form of the virus can afflict pigs and boar with hemorrhaging, fever, a loss of appetite and energy, red or purple skin patches, skin ulcers, breathing problems, plus diarrhea and bloody vomiting.

Authorities are not yet sure how African swine fever jumped thousands of kilometers west, despite serious containment measures.

The disease is highly contagious and resistant. It can be spread through many forms of contact, for example being inhaled through the air or carried by vectors such as ticks. It stays in the environment for months and is transmitted to animals through contact with infected boar or pigs, contact with contaminated clothing or objects — and even through eating infected meat.

Most infected animals die within 10 days, according to the European Food Safety Authority, which produced a cartoon illustrating the suffering of the sick pigs. There are no known cures or vaccines.

2) Where is it now?

African swine fever (ASF) first reached Europe in the late 1950s and was only pushed out in some places in the 1990s. It remains endemic on Sardinia, however.

The disease re-entered Europe in 2007, in Georgia, from where it quickly spread to Armenia, Azerbaijan, Iran, Russia, Belarus and Ukraine. It crossed the border into the European Union — to Estonia, Latvia, Lithuania and Poland — in 2014.

Despite emergency containment measures ordered by Brussels, ASF hit the Czech Republic in 2017. The situation started to spiral this year. It reached Hungary in April, and then Romania started reporting serious outbreaks on pig farms — prompting the slaughter of some 140,000 animals on a single farm as well as accusations of deliberate meddling from rivals out to undermine the country's pork industry.

China, the world's largest pork producer, had its first outbreak in August. Bulgaria then notified a case of African swine fever later in the month.

Belgium's is the latest notification. Food safety authorities said Thursday that they have identified two boar carrying the disease.

3) What has the European Commission been doing?

The EU has responded to ASF with rules designed to prevent its spread, such as designating infection zones and limiting the transport of pigs within them.

A European Commission spokeswoman said Thursday that Belgium would mirror measures used by the Czech authorities, which include restricting access to the infected zone, patrols to find boar carcasses and increasing biosecurity measures on pig farms, among other things.

4) How did the disease jump to Belgium?

Authorities are not yet sure how African swine fever jumped thousands of kilometers west, despite serious containment measures.

Should trade partners ban all EU pork imports — as was the case with Russia in 2014 — Germany and Spain would be the most at risk.

Belgium's food-safety agency AFSCA suggested Thursday that travelers coming from an infected zone in the east could have unwittingly transported the disease with them. The idea is that a ham sandwich discarded by the roadside, for example, could have been eaten by a boar. The virus can also be carried on objects, such as boots.

5) Why is the spread to Belgium significant?

Europe's pork industry is concentrated in Western Europe — especially in Germany, France, Spain and Denmark.

Each of these countries had been hoping to keep African swine fever contained east of their borders, to avoid possible trade damage. Belgium's food agency will also want to avoid another international food crisis: It drew intense criticism in 2017 for its handling of the fipronil eggs contamination crisis.

6) What are the trade risks?

Europe's a big pork exporter — and countries stand to lose if governments around the world impose import bans.

In 2016, the EU produced a total of 23.6 million metric tons of pigmeat, accounting for 20 percent of world production. Of that, the EU exported 4.16 million tons to world trade partners, or 17.6 percent of the bloc’s total production.

While these exports are at stake should African swine fever spread further, decisions over whether non-EU countries will block imports are more complicated. Areas where trade restrictions are in place depend on whether an outbreak affects wild boar or domestic pigs.

There is also a generally accepted agreement among trade partners that there should be no blanket ban on a country's imports due to the EU’s application of “regionalization.” This allows trade from non-affected areas in the EU to continue without disruption. China is a notable exception, having imposed country-wide bans.

Other key export destinations are also beginning to close their ports to some European pork. Serbia, Japan, Taiwan, Singapore and South Korea have banned Hungarian pork exports, for example, while Vietnam is stopping pork shipments from a range of EU countries.

Should trade partners ban all EU pork imports — as was the case with Russia in 2014 — Germany and Spain would be the most at risk. German pigmeat production accounted for 5.5 million tons, or 23 percent of total EU production, in 2017, while Spain produced 4.2 million tons, or 18 percent of total production.

According to 2017 data, China is by far the biggest importer of EU pigmeat, with around 40 percent of EU pigmeat exports currently going there. This is followed by Japan, South Korea, Hong Kong, the Philippines, and the U.S.