It’s likely that thousands of people who had Covid-19 were never confirmed as Covid-19 cases. Some were just asymptomatic, some had the symptoms but no access to tests, and some had symptoms but were so early in the outbreak that no one considered Covid-19 as a diagnosis.

An example of the latter is the case of the California woman who died on February 6, long before there were thought to be cases in California. An analysis of a tissue sample shows she died of Covid-19. The same was true of another California death, on February 17. Health officials conclude that the virus was circulating in California in January.

Separately, scientists modelling the outbreaks in cities are concluding that thousands of people must have been infected before the first confirmed case. For example, by the time New York City had its first confirmed case, on March 1, there were probably already over 10,000 people infected in the city, according a disease model at Northeastern University.

When did Covid-19 come to the suburban counties near us? I bring this all up because I have been trying to understand when Covid-19 might have come to the Kendal area.

Let’s start with confirmed cases. It isn’t too hard to determine when the first Covid-19 case was confirmed in Chester County (where Kendal is located). It was March 13. You can find this information on the dashboard maintained by the county Health Department. It can also be found in the New York Times database of county-by-county cases. (If you have a spreadsheet program and time on your hands, you can check on Covid-19 cases and deaths anywhere in the country by downloading the Times’ data, which is updated daily.)

The timeline is a bit murkier where our neighboring suburban counties are concerned. According the Times’ database, Delaware County (our neighbor to the east) was first to get a confirmed case, on March 6. In fact, it is shown as the first case in all of Pennsylvania in that database, and was probably a factor in the Governor’s announcement of a “state of emergency” on that day. The Delaware County dashboard, however, indicates that the first Delaware County case wasn’t until March 9. Regardless, by the time Chester County got its first confirmed case on March 13, Delaware County already had 6.

Montgomery County, to the northeast of us, was right behind Delaware County, with a confirmed case on March 7. By March 13, it was already up to 18 cases. New Castle County, Delaware (south of us) had its first confirmed case March 11. By March 13, it was up to 4 cases.

So it is clear that Covid-19 was already spreading in our vicinity (particularly to the east and south of us) by March 13, when our county had its first case. It took another week for cases to start appearing in the data for Lancaster County (to our west) and Berks County (to our north).

Covid-19 was probably circulating in February. Did it miss us? The early cases listed above were being confirmed the second week of March. Given the roughly 2-3-week lag taken by the infection-symptoms-confirmation-reporting process described in an earlier post, it seems likely that the virus must have been circulating in the neighboring suburbs in mid-to-late February.

The protective measures at Kendal only really began to be implemented on March 11. Were we just lucky that no one happened to bring the virus into Kendal between mid-February and March 11? Or did we actually have the virus here, but we were lucky that no cases were serious enough to result in testing and diagnosis? One way or the other, we were incredibly fortunate. Most other retirement communities in our area have been struggling with serious outbreaks, and the seeds for those outbreaks might well have been planted in February.

Somehow, Kendal was spared. The protective work done by our administration and medical staff deserves enormous credit for protecting us since mid-March, but how did we escape the virus before that? That question may never be answered.