Conditions at U.S. meat plants contributed to increased risk of coronavirus infections, which ultimately led to more than 4,900 workers getting sick, according to the Centers for Disease Control and Prevention.

The agency cited difficulty maintaining social distancing and adhering to the heightened cleaning and disinfection guidance among the factors that increased risks for workers. There were 20 deaths among employees as the virus spread to 115 meat plants across 19 states, the CDC said in a report today, citing data covering April 9‒27.

Experts, unions and advocacy groups have warned that meat companies failed to protect employees adequately as the virus spread quickly and then forced plant shutdowns. The rapid spread of the disease underscored how lower-income U.S. workers became more vulnerable in the pandemic era. “Socioeconomic challenges” might have contributed to employees continuing to show up for work, even if they felt ill, the CDC said. Some companies offered bonuses for attendance, which may have further encouraged sick people to come in.

Meat-plant employees are among some of the most vulnerable populations. The positions are often filled by immigrants, since many U.S. workers shun the grueling and sometimes dangerous work. The jobs are often low-paying, and it’s a work environment where sick leave is rare and even bathroom breaks are considered a perk. At some plants, virus infections ran as high as 18%.

A wave of outbreaks at meat plants ruptured the nation’s supply chain for protein, sparking shortages at grocery stores. Shutdowns at major slaughter plants started in early April. Even though the industry faced only a dozen closures, producers have such a stranglehold on output that few remedies are available when even a handful of facilities are down. Beef and pork prices are surging, and farmers were forced to destroy tens of thousands of animals.

With President Donald Trump invoking the Defense Production Act this week to keep plants running during the pandemic, unions are sounding the alarm that workers will continue to face dangerous conditions.

“The president’s executive order will only ensure that more workers get sick, jeopardizing lives, family income, communities, and, of course, the country’s food supply chain,” said Kim Cordova, president of Local 7 of the United Food and Commercial Workers International Union, which represents 3,000 workers at the JBS SA beef plant in Greeley, Colorado.

Get Used to Expensive Meat With Supply Woes Lasting All Year

At huge plants handling thousands of animals a day, employees are jammed into elbow-to-elbow processing lines that run at lightning speeds.

“The pace and physical demands of processing work made adherence to face-covering recommendations difficult, with some workers observed covering only their mouths and frequently readjusting their face coverings while working,” the CDC said.

Low-paying jobs also mean workers face tough living conditions at home, where multiple families are sometimes sharing the same dwellings.

English is often the second language for many workers, and some unions have cited a lack of proper signs outlining virus-prevention methods in multiple languages. The CDC cited language barriers as a risk factor, reporting that one facility reported a workforce with 40 primary languages.

Some experts and unions have warned that reopening shuttered plants may further disrupt the supply chain. Workers probably will continue to get sick, leaving the industry short-handed and struggling to run at full capacity.

“It’s a bad idea,” said Kooper Caraway, president of Sioux Falls AFL-CIO, which represents 3,700 workers at Smithfield Foods Inc.’s South Dakota pork plant. “If the intention is to make sure that the production is not slowed down too much, this is a short-sighted measure that will end up slowing production more than it would have.”