Preliminary results from @hendrikstreeck et al:

15% of population in Heinsberg (Germany) have evidence of past or current infection with #SARSCoV2.

Based on ~500 people from 400 households (out of a representative sample of 600) who chose to participate
https://www.land.nrw/sites/default/files/asset/document/zwischenergebnis_covid19_case_study_gangelt.pdf

If 15% of the population were truly infected by #SARSCoV2 in Heinsberg,

then we could expect >15% of infected in Madrid and New York City

because the proportion of confirmed #COVID19 cases (as % of population) is
~0.5% Heinsberg
~0.7% #Madrid (underestimate)
~1.0% #NYC