COVID in your house? Isolating from sick family members may not do much good, according to a new study

For the record, not all experts agree.

Close contact seemingly didn’t increase risk

Researchers followed 88 adults who tested positive for COVID in 2020 and 2021, in addition to their 252 household contacts. They used proximity sensors to track how close each ill person was to other household members, how many times, and for how long, over a two-week span.

When the study was done, they came to a few conclusions. Among them: that females were more than twice as likely to contract the virus, and that being obese appeared to increase one’s chance of coming down with it.

Most surprising, however, was this finding: Close contact didn’t seem to increase the likelihood of other household members becoming infected. Sleeping in the same room didn’t seem to raise the risk either.

Just how COVID spreads has been a topic of contention since the beginning of the pandemic. It undoubtedly spreads long-range via aerosols. But it can also spread shorter range via droplets—moisture particles that are larger than aerosols, like drops of saliva expelled when a person coughs. Just how frequently the virus is transmitted via droplets is unknown—but perhaps not as frequently as we think, the authors contend, citing the study’s results.

Given that airborne transmission appeared to rule the day, the findings “emphasize the important role that increased ventilation may play in reducing secondary transmission” of COVID in households, senior study author Stefano Tempia—an epidemiologist and associate professor at the University of the Witwatersrand in Johannesburg, South Africa—said in a news release about the research.

COVID can transmit via surfaces, too

A word of caution, however, before you pack up your laptop and snacks and head back to the living room: The study only focused on transmission via air, and not on other ways the virus could be transmitted, like via objects and surfaces, Bruce Y. Lee,  professor of health policy and management at the City University of New York School of Public Health, told Fortune.

An April study published in The Lancet Microbe found that 52% of those who lived in the same household as someone with COVID became infected themselves. When swabbed, those with COVID RNA on their hands were more likely to eventually test positive for the virus, signaling the importance of household surfaces in the transmission of COVID—not just air.

Other factors the study didn’t appear to consider when it came to household contacts, according to Lee: “If they do have less or more face-to-face contact, are they wearing masks? Are they closing their doors? How well are they cleaning? How frequently are they washing their hands?”

It’s worth noting that study participants generally live in poorly ventilated houses, and didn’t have much opportunity to distance from others in their homes. The majority live with three to five other people, and almost half only have one or two bedrooms, the authors wrote. 

The same study conducted in well ventilated houses with heating and air conditioning might show that distancing makes more of a difference in household transmission, they noted.

It’s also worth noting that participants were infected with the earlier, generally more severe Alpha, Beta, and Delta variants, which didn’t spread as effectively as the current Omicron strain does.

Official advice on isolating with COVID

The U.S. Centers for Disease Control and Prevention still recommends staying home for at least five days if you test positive for COVID, and isolating from others in your home. The agency also recommends wearing a high-quality mask if you must be around others, using a separate bathroom, and using different household items like cups, towels, and utensils.

Five days may not even be long enough, Lee pointed out, referencing studies that have shown some shedding the virus for up to 10 days, or even longer. The CDC’s initial recommendation for isolating in 2020 was 10 days.

“If you want to be safe, aim for 10 days,” Lee said.