Concerning Rise in COVID-19 Cases

There has been a concerning rise in COVID-19 cases in Allegheny and Westmoreland counties in the past week. Westmoreland county has had more new cases per capita over the last 14 days than Allegheny, and their case numbers are growing more rapidly. Allegheny Health Department Directory Debra Bogen gave a press conference about it today.

Statewide the new case counts have continued to slowly decline. However, several states, especially Florida, Texas, and Arizona, have seen large recent increases in new case counts.

As a result Allegheny county will likely see an increase in cases being seeded from out of state. In Dr. Bogen’s press conference she stated that a majority of new cases traced over the weekend were people who had traveled out of state during the period they were likely infected.

The effect that this will have on our overall rate of new cases will depend on the reproduction rate $R_0$. An $R_0$ greater than 1 results in exponential growth. This preprint paper estimates that $R_0$ was 6.7 in New York state before mitigation measures were implemented.

Given the decline in new daily cases in Pennsylvania and Allegheny county in April and May, the $R_0$ was brought lower than 1 through social distancing, contact tracing, and wearing masks. Assuming $R_0$ is still below 1 but above 0, seeded cases from out of state will still multiply based on the sum of a geometric series.

As an example, if 10 cases are seeded, and $R_0$ is 0.75, the total number of infections will be:

$10+7.5+7.5\times0.75… =\frac{10}{1-0.75}=40$

If $n$ is the number of seeded cases per day, and $R_0$ is the reproduction number, the general equation for the total number of new cases per day will be:

$\textrm{Total}=\frac{n}{1-R_0}$

Therefore it is important to keep the reproduction number below 1. If case numbers rise to the point that people are afraid to engage in economic activity, it will be just as economically damaging as shutdown measures, but with a large number of fatalities in addition.

Fortunately there are two mitigation methods that can keep the reproduction rate low that are much cheaper and less disruptive than a shutdown, provided they are implemented well.

Wear Masks

The scientific evidence is clear that wearing masks reduces SARS-COV-2 transmissions, and that the effect is large. This paper shows that areas that mandated face masks in public reduced their COVID-19 transmissions.

Allegheny county should evaluate measures to improve mask wearing compliance. This should include public education on how to wear a mask properly. I see people in public wearing masks that don’t cover their nose. The county should consider mandatory educational posters in establishments open to the public explaining how to correctly wear a mask.

Improve Our Contact Tracing

After mask wearing, contact tracing is the next most cost effective way to reduce transmissions.

In her press conference Dr. Bogen stated “We have done case investigation of every case and contact traced every case, and will continue to do that.” (jump to the 20 minute mark of the press conference I linked to earlier). If Allegheny county has been able to thoroughly trace every case that would be impressive. Other states that have hired more contact tracers per capita have struggled to do that.

This New Yorker article describes the development of Massachusetts contact tracing program. This New York Times article describes the development of New York City’s contact tracing program. In New York City, only 35% of individuals who tested positive provided information to the contact tracers who attempted to contact them. For the Massachusetts program, the number was 74%.

The Post Gazette had a recent article on Pennsylvania’s contact tracing program. Pennsylvania and Allegheny county both have far fewer contact tracers than experts recommend. Pennsylvania and Allegheny county both have far fewer contact tracers per capita than New York City and Massachusetts. Both New York City and Massachusetts have supplemented Federal funding with local funding sources to increase the number of tracers.

Table 1

	Cases per 100,000 over 14 days prior to June 18, 2020	Contact tracers per 100,000	Contact Tracers
Massachusetts	63.24	14.51	1000
New York City	43.06	35.72	3000
Pennsylvania	49.17	4.69	600
Allegheny County	12.91	2.06	25

In an email to me, Amie Downs, the Allegheny county director of communications, stated, “The number shown [14] in the [post gazette] article reflects the number on the date they asked, which was several weeks ago. We have since started additional contact tracers, have ACHD staff that can shift to those roles, and have trained medical students and medical corps volunteers as well if we see an increase.”

So the number of contact tracers in Allegheny county is higher than shown in the table, but I am not aware of a published source with a more recent number.

In order to allow a better assessment of the county’s contact tracing performance, the county should regularly publish the following information:

• How many contact tracers are currently in the program.
• What percentage of positive tested individuals respond to contact tracer questionnaires.
• How many contacts on average are reported for each positive tested individual.
• What percentage of these contacts are able to be contacted, and of those what percentage get tested.
• What is the time delay from when someone gets tested until their contacts get tested.
• What percentage of people who test positive have housing situations that make it difficult to isolate effectively.

Having measurable performance benchmarks will allow us to drive improvements to the program.

Finally, the most effective contact tracing programs provide support for individuals who test positive to isolate. Ideally, this includes providing them with a hotel room to keep them from spreading the disease to roommates and family, and having food delivered. New York city has done this on a voluntary basis. The countries that have been most successful at containing the spread of the virus have made it mandatory.

Allegheny County has done better than most of the United States so far at responding to COVID-19. However, we have lagged behind the countries like Taiwan and South Korea that have done the best in the world. If we settle for our current performance there will be avoidable deaths. We can do better.

Update:

I revised the table on June 24, 2020 to include the latest number of contact tracers. In a press conference on June 24, 2020, Debra Bogen stated Allegheny county has 10 people conducting case investigations and 15 people performing contact tracing. See the 12 minute mark of the video.

In a separate press conference on June 24, Governor Wolf said Pennsylvania was ‘on its way to 600 contact tracers’ (see the 28 minute mark of the video).

The original June 23 version of this post had dated contact tracing numbers from this Post Gazette article.