If you are wondering why San Francisco has instituted a 10pm curfew and tightened shelter in place restrictions to purple tier, it is because new infection rates are higher than they have ever been in San Francisco. Our local government displays the COVID data they collect and continuously updates it online.

We are now averaging 137 new confirmed cases a day in our city. Below you can see that the first big ‘surge’ of new cases per day was in July/August and at it’s peak was averaging 131 new cases a day.  November’s infection rates are now greater than in any previous time period, and unfortunately only appear to be rising.

To view this graph go to: https://data.sfgov.org/stories/s/dak2-gvuj

Map of New Cases in SF

Interactive maps can be found at https://data.sfgov.org/stories/s/Map-of-Cumulative-Cases/adm5-wq8i#new-cases-map

Since the government is not able to test every resident, they have to rely on the data they can collect.  Namely the population that is voluntarily coming forward and being tested. From that sample size of a neighborhood, they calculate the positive test rate in an area.

For example, the Marina Neighborhood has a total population of 25,331 (based on census numbers). Over the last 30 days, there have been 124 confirmed new cases of COVID in that population. That is less than half a percentage of the Marina’s total population. BUT, they have to assume that a greater number of infected individuals are not being tested.

So the government and its infectious disease experts, compare the positive test rates in the neighborhoods to positive rates in prior months, and calculate the potential spread of the virus if left unchecked in a population.  In the Marina’s case, the positivity rate drastically increased compared to last month.  And this has happened in several neighborhoods in San Francisco. The positivity rate is highest in Hunters Point, Mission, Portola, Presidio Heights and the Marina neighborhoods, but we live on a peninsula, so this is obviously all of our problem.

The purple tier restrictions and regulations are not being instituted for no good reason.  Please read about them and help your city, by not helping to spread the virus:  https://sf.gov/news/sf-assigned-states-purple-tier-will-roll-back-many-non-essential-activities