Indigenous people face a unique risk that is not fully understood, a W.H.O. official said.

Countries across the Americas must do more to help Indigenous communities prevent and treat Covid-19 infections — and that starts with collecting far more extensive and reliable data, a leading World Health Organization official said on Wednesday.

“While each group is unique, no matter where you look, our Indigenous communities are more vulnerable to Covid infections,” said Dr. Carissa Etienne, the director of the Pan American Health Organization, which is part of the W.H.O.

Nearly half of the more than 62 million Indigenous people in the Americas live and work in urban centers and travel home to visit their communities, a pattern that increases the chance of viral transmission. Many also hail from communal societies, which makes social distancing a challenge.

“This frequent movement and gathering creates opportunities for Covid to spread,” Dr. Etienne said. And even in urban centers, Indigenous people face “invisible barriers” to care, including language and poverty, she said.

Yet reliable data on Covid’s impact on Indigenous people is itself in short supply. Most countries in the region collect no figures at all on Covid’s effect on Indigenous people. Based on the limited information reported to the W.H.O. by a few countries, including Brazil, Colombia, Ecuador and Peru, at least 617,000 Indigenous people have been infected with Covid-19 in the Americas and nearly 15,000 have died.

“It is likely that many more have been infected and many more have died, but we may not know it because they have struggled to get the Covid care that they deserve,” Dr. Etienne said. “For many of our Indigenous people, the right to health remains a promise unfulfilled.”

Dr. Etienne urged countries to collect “more and better data” that she said was “essential to guide effective policies,” and would help public health efforts to “understand and resolve the challenges that are facing our Indigenous groups.”

“Too few countries collect data on the pandemic’s impact across ethnic groups,” she added, “leaving ministries of health blind to important and valuable trends on how the virus is affecting our Indigenous communities.”

The call for increased attention to Indigenous people comes as more than 1.2 million Covid-19 cases and 20,000 deaths were reported in the Americas over the past week.

Covid infections are rising in North America, primarily because of an increase in cases in the southern and eastern United States as well as in central Mexico. Infections are climbing in Guatemala, too, particularly among people younger than 50.

Among Caribbean nations, Cuba, Martinique and the British Virgin Islands are experiencing particularly sharp increases.

Vaccines “remain out of reach for too many people,” Dr. Etienne said, noting that only 18 percent of people in Latin America and the Caribbean have been fully vaccinated against Covid-19.

There was some good news in much of South America, where case numbers are largely dropping, although some Brazilian states have seen an increase in infections. Twenty-two countries in the Americas have detected the Delta variant as of this week, although so far it has largely been associated with travelers.