As vaccinations ramp up and cases decline, U.S. officials relaxed recommendations for one of the groups hit hardest by the COVID-19 pandemic: elderly people in nursing homes.
Experts say the high death rates at long-term care facilities may be one reason why the impact of the pandemic has in many cases been greater in high-income countries than in less wealthy nations.
After months of isolation aimed at preventing infection in this extremely vulnerable group, federal guidelines no longer advise against visiting elderly relatives indoors at these facilities.
"CMS recognizes the psychological, emotional and physical toll that prolonged isolation and separation from family have taken on nursing home residents, and their families," said Dr. Lee Fleisher, chief medical officer at the U.S. Centers for Medicare and Medicaid Services (CMS).
Cases and deaths have declined sharply as vaccinations reached this top-priority group. Unless community transmission levels are high, and less than 70% of residents have been vaccinated, CMS now recommends allowing indoor visits.
COVID-19 has extracted a devastating toll on nursing homes. More than a quarter of all COVID-19 deaths recorded in the United States have been among nursing home residents, according to CMS data.
Death rates from COVID-19 increase with age. Infection rates increase where people congregate for long periods of time indoors. Nursing homes put the two together.
It is a combination that does not happen in much of the world, said University of California San Francisco epidemiologist George Rutherford.
"There is no such thing as nursing homes in lots of countries," he said. "There's no concentration of the frail elderly at certain centers. You end up with intergenerational households, which create their own problems, but you don't have that kind of massive outbreak waiting to happen."
The pandemic has caused death and disruption around the world. But many of the highest rates of death by population have clustered in higher-income countries, including the United States and much of Europe.
These countries tend to have older populations. Italy has among the highest COVID-19 death rates in the world and a median age of 45. Nigeria, on the other hand, with a median age of 18, has among the world's lowest.
"People are much younger in low- and middle-income countries," Rutherford said. "People are getting sick, (but) it's not being played out in terms of mortality."
Age is not the only factor, experts say.
COVID-19 also kills more people with other medical problems such as diabetes, obesity, and heart and lung disease, and "there are just simply a lot more of those diseases represented in high-income countries," said Judd Walson, vice chair of the global health department at the University of Washington.
Everyday life is different in many ways in higher- and lower-income countries, Walson added.
Office work predominates in wealthier countries. That may involve dozens or even hundreds of people from miles away, all with their own social networks, coming together to work indoors for hours at a time.
"You can imagine, if one individual is infected in any of those networks that the spread can be enabled quickly," Walson said.
Fewer people are working in offices in lower-income countries, Rutherford noted. More people are working in agriculture, for example.
"People work outside," he said, "so what that means is, they're not getting infected in the first place."
Leisure is also different in lower- and higher-income countries. Public health officials in much of the United States and Europe have closed or restricted bars and restaurants to prevent large groups of people from gathering indoors. But Walson noted that in many lower-income countries, especially in the tropics, bars and restaurants are open to the air.
On the other hand, there may be more cases of COVID-19 in lower-income countries than are being reported, thanks to a lack of resources for testing and weak health systems in general.
In a study that's in progress in Kenya, Walson found that getting accurate numbers is a challenge "for reasons that I think everyone can appreciate and also some reasons that I found a little surprising."
Fear and stigma surround COVID-19, which discourages people from getting tested, he said.
But people also were afraid that if they tested positive, they would be quarantined in a hospital and charged for their time there.
"There was a fear of the financial implications of a positive test that was keeping people away from testing," he said.
COVID-19 presents a challenge to under-resourced hospitals, and not just in terms of patient care. If a patient already admitted to a hospital were to test positive, they would have to be isolated along with anyone else they may have exposed, and many hospitals are not set up for isolation.
Health care workers would also need to be tested and possibly quarantined, and "they're already understaffed," Walson said.
"There's a reluctance to find out that somebody might have COVID and then have to figure out what you're going to do," he added. "The implications of a positive test are considerable."
But death rates are not lower simply because people are not counted. In his study, Walson said, "We're certainly detecting cases, but we're detecting lower numbers of cases than I think we had feared. And that's a very good thing."