They have been packing and delivering supplies, caring for the sick and elderly, and keeping streets and buildings clean.

They have also watched their co-workers fall ill. Thousands have gotten sick themselves. Many have died.

The burden has been borne unevenly across gender, racial and socioeconomic lines, according to an Associated Press analysis of census data in the country’s 100 largest cities. They are mostly women, people of color and more likely to be immigrants.