China’s transportation officials are recommending flight attendants wear disposable diapers and avoid restrooms at all costs on flights serving countries with high rates of coronavirus cases, according to documents from the Civil Aviation Administration of China (CAAC).

The recommendation to employ diapers and avoid in-flight bathrooms altogether applies on flights to and from countries with infection rates exceeding 500 cases per million people. The United States’ coronavirus case rate exceeds that limit as of Dec. 10, at more than 660 cases per million.

The guidance is part of a lengthy document detailing technical guidelines for preventing the spread of the coronavirus on planes, which also states that flight and cabin crew should, on lower-risk flights, designate their own private lavatory and sanitize it before and after every use. The document was issued on Nov. 25, according to CNN.

The advice to wear a diaper falls under a section covering recommended personal protective equipment.

“Personal protective equipment for cabin crew: surgical masks, double-layer disposable gloves, goggles, disposable nonwoven hat, disposable gown, disposable shoe covers. Flight attendants are advised to wear diapers,” the CAAC states. “Avoid using restrooms unless under special circumstances to decrease risk of infection.”

Studies in recent months have suggested that plane cabins are lower-risk coronavirus environments than previously thought when passengers wears masks. But doctors have also signaled that lavatories on long-haul flights are at a substantial risk of being contaminated with the coronavirus. According to reporting by The Washington Post, Boeing is developing airplane lavatories that can sanitize themselves in under three seconds.

David Freedman, an infectious-disease expert at the University of Alabama at Birmingham who frequently reviews travel-related covid-19 studies, told The Washington Post that passengers should avoid airplane bathrooms when possible. He says of the risks associated with long-haul flights: “Longer flights have more of a chance for bathrooms to become contaminated.” On shorter flights, more passengers are likely to skip the plane bathroom altogether.

Long trips, like 15-hour journeys between the United States and China, also introduce more exposure to others, doctors say. A recent study by New Zealand health officials found that an infected man on an 18-hour flight to the country spread the coronavirus to at least four other passengers, although the mode of transmission has not been verified.