Natalie E. Dean, PhD+ Your Authors @nataliexdean Assistant Professor of Biostatistics at @UF specializing in emerging infectious diseases and vaccine study design. @HarvardBiostats PhD. Tweets my own. She/her. May. 13, 2020 1 min read + Your Authors

Per request, adding a more accessible interpretation. ☺️ This survey used random sampling to invite households to participate. This is higher quality than volunteer-based surveys and should be more representative of the general population.

They tested 4600 people using PCR (to detect virus) and serology (to detect antibodies indicating prior infection). 1.7% of people were either acutely infected or had been infected recently enough that they were still shedding viral particles.

In addition, 1.1% of people had antibodies. This number is likely uncertain as these tests can yield false positives, but overall the results indicate low levels of infection in the community. This is consistent with studies in other areas that have not had massive outbreaks.

We can use these results to estimate the total number of infections in the population (2.8% of the state is 186K infections). Since the state has confirmed 19,000 cases, this means they are detecting about 1 in every 11 infections.

These numbers are consistent with other studies that many infections are missed (11x), but not 50x as some think. In the study, about half of people who were either PCR or antibody positive reported no symptoms, though there can be issues with recalling mild symptoms.

They compare the total estimated number of infections to the number of known deaths in the state, and this gives us an estimate of the infection fatality ratio (IFR). It is about 0.6%, which is consistent with other studies. This means it is much more severe than the flu.

You can follow @nataliexdean.


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