SLO County should see big drop in COVID cases by mid-April — if we follow ‘shelter at home’ rule

First the facts about the coronavirus so far as they are known.

The coronavirus is highly infectious. New cases arise from exposure to an infected human. The period of time between exposure and symptoms is generally 5 days up to, at most, 14 days. Therefore, if one is exposed to someone who is infected with the coronavirus and then has no symptoms for 14 days that person is virus-free and not infectious. (Only many months from now, when there is a blood test for coronavirus antibodies, will we know how many asymptomatic infections there were since people who are infected — whether they are symptomatic or not — generally develop antibodies, which is what keeps them from getting infected again).

It is expected and not surprising that the daily number of new cases in San Luis Obispo County is rising because most of these cases were acquired before the directive to shelter at home on March 19. People who had the virus but didn’t know it prior to that date mingled freely at home and at work and in the marketplace, spreading the infection. With a 5 to 14 day incubation period we are now seeing the results of that spread.

If our local pattern is followed, then the numbers will continue to go up to around 18 to 20 new cases per day by March 29 and will hit a peak of around 40 new cases per day by April 2.

By April 3, 14 days after people on March 20 became aware of and responded to the directive, the number of new cases will drop by 50% or more to less than 20 per day. If the shelter-at-home policy is strictly followed by everyone in the county, the numbers will then drop to zero new cases per day. How long it takes us to get to zero new cases per day will depend on our response to this directive. One can neither pass the virus on nor get it from an outside person if one is at home for 14 days.

However, this is not a perfect world and it may be that some people will only take the directive seriously when there is potential enforcement. This may be instituted around March 26, so it may be 14 days later (i.e., April 10) before the number of new cases gets near zero. In either case, the dramatic drop in new cases will reinforce the wisdom of the directive.

Can the restrictions be lifted on April 10 or thereabouts when no new cases are seen in the county? No, since the incubation period is up to 14 days, one must wait an additional 14 consecutive days with zero new cases (or to April 24 or thereabouts) to be sure the county is virus-free. And efforts to shelter-at-home will need to be re-doubled during this time to ensure there are no new cases. At that point, given that all people who are still recovering are appropriately quarantined, the county can announce that it is virus-free and businesses and the marketplace can return to normal.

Of course travel into or out of our county is not prohibited (and having zero new cases for 14 consecutive days by April 24 or thereabouts is optimistic). Therefore, there will still be occasional new cases. Thus of equal importance during this time will be the need for the Public Health Department to aggressively pursue any new case, no matter what its source. Each case will require immediate testing including all family members living at home, all contacts and all contacts of contacts with appropriate isolation and quarantine as needed so that the public can be assured that it is safe to resume normal activities and that any new case is being kept from spreading.

Look for these dates:

• April 3 or thereabouts: A dramatic drop in the number of new cases (the degree of this decrease will show how well our county has been sheltering-at-home)
• April 10 or thereabouts: Another big drop in new cases secondary to those who took more heed of sheltering-at-home as of March 26
• April 24 or thereabouts: If we can achieve 14 days with zero new cases beginning April 10 and if Public Health will aggressively pursue all contacts of any new case then restrictions can be lifted.

We can get back to work, to education, to shopping, to entertainment, but we must act together to achieve this.

There is hope for San Luis Obispo County, and by extension for California if all counties and health departments cooperate.

Dr. Steven B. Jobst is a retired pathologist who has lived and worked as a physician in San Luis Obispo County for more than 30 years. He has also taught part-time at the Medical School at UCLA.

This story was originally published March 27, 2020 at 8:34 AM.