A Wall Street Journal analysis found that, across the country, the virus has spread more widely in places with the most crowded households, not necessarily places with the largest or densest populations. Remote, rural hamlets where extended families live under the same roof have turned deadlier than some of the densest blocks of Manhattan or Chicago, the analysis found. In both contexts, the virus has zeroed in on crowded homes, sometimes wiping out generations in a matter of days…

The Journal analyzed all 1,487 U.S. counties with at least 50 Covid-19 cases, as of June 7. The 10% with the highest rates of crowding accounted for 28% of the coronavirus cases among those 1,487 counties, according to census and Johns Hopkins University data.

The Journal also found that in selected areas—including Cook County, Ill., New York City and Wayne County, Mich.—ZIP Codes with the largest share of households of at least five people have disproportionate shares of their counties’ Covid-19 infections. The problem is particularly acute in poorer and minority communities, according to data from some cities, where extended families often live together and lack space and resources to isolate anyone who falls ill.