As a second installment to this column on pandemic highlights and COVID-19 science, I've chosen to focus on our local outbreak with a few notes about herd immunity.
The short of it
On herd immunity: Achievable only through vaccination or widespread infection, herd immunity is likely still many months away. Renewed commitment to mitigation efforts is key to stopping COVID-19.
On the local outbreak: Hamilton County is undergoing its most severe outbreak since peak spread in July. Masks are mandated with a few exceptions. Contact tracing and testing continues, crucial to stopping the spread of disease.
On herd immunity
Readers may have heard the term herd immunity many times by now. This refers to the widespread immunity in a population against a disease that prevents the disease from maintaining its hold in that population. When a disease spreads, it requires people who are susceptible to the disease to perpetuate its spread. However, when there are not enough susceptible people, the disease can no longer spread and consequently dies out. An estimated 70% of the population will have to be immune to achieve herd immunity, a proportion reached either through natural infection or vaccination.
Herd immunity through natural infection is far more costly and harmful than immunity through vaccination. Given the estimated case fatality rate for COVID-19 and the lack of a cure, this kind of widespread infection will likely only come with incredible suffering and many deaths. Mitigation efforts, such as routine testing and contact tracing, are important to preventing this route to herd immunity.
Herd immunity may also be achieved with a vaccine. No vaccines are yet approved in the U.S., though several are currently in development. These are projected to be ready sometime in the spring of 2021 and will be issued through a priority framework. This means that certain populations will have priority for receiving a vaccine. Operation Warp Speed, the U.S. vaccine distribution strategy, will give priority to those who are most at risk for getting infected and transmitting the virus, including frontline health workers, and those at greatest risk for severe illness, such as the elderly and those with significant underlying illness.
In the absence of a vaccine, the most effective means of stopping the pandemic are mitigation efforts. It is possible to control the spread of COVID-19, yet doing so requires that communities work together with their community leaders and local governments, maintaining strong commitments to the safety guidelines and supporting testing and tracing efforts.
On the local outbreak
By local I mean, of course, Hamilton, Dade, and Walker Counties.
Hamilton County is experiencing a very aggressive outbreak with currently the most severe level of COVID-19 spread in the county's risk level metric. The rate of spread in the past week was about 35-40 daily new cases per 100,000 people, or a little over 100 new cases per day. New cases are concentrated in the following zip codes: 37343 (Hixson), 37421 (East Brainerd) and 37363 (Ooltewah). Current hospitalizations are climbing, nearing the highest levels reached toward the end of July. This comes after a relative dip in September and October.
Because of this increase in cases, the Hamilton County Health Officer Dr. Paul M. Hendricks, MD, issued Health Directive No. 3 on October 9, 2020, saying that until November 22, all persons inside public and private buildings must wear a mask. Additionally, businesses are directed not to serve customers or clients who do not wear a mask, and those who fail to enforce this or clients who choose not to wear a mask may receive a civil citation. There are a few exceptions to the rule, however; for example, private schools may write and follow their own policy in response to the pandemic.
The University of Tennessee at Chattanooga (UTC) is also experiencing a severe outbreak, with approximately 5-10 new cases each day since August and between 250 and 300 students currently in quarantine or isolation.
In response to this rapid spread of COVID-19 in Hamilton, the Hamilton County Health Department (HCHD) continues to contact trace, talking to those who have tested positive for the virus to determine who they have come into close contact with. Close contacts are asked to quarantine and are assigned to a contact monitor from the HCHD to monitor symptoms. Contact tracing is a highly effective measure used to slow the spread of a disease.
COVID-19 testing also continues as a central measure for understanding the spread and distribution of the disease. There are many places to get tested, including the Alstom Plant on Riverfront Parkway and several local clinics such as Cempa Community Care, Clínica Médicos and LifeSpring Community Health. Testing is offered on the weekends. More recently, many places are offering the rapid test in addition to the PCR test. The rapid test provides results in 15 to 30 minutes but is usually only used on individuals who have symptoms of COVID-19. The PCR test must be sent to a lab for processing; results are usually received in 24-48 hours.
Dade County is reporting a much less aggressive spread of disease, with only 410 cases and 6 deaths as of November 10, reported since the end of March. Walker County has reported 2,094 cases and 47 deaths as of November 10. As a comparison, Hamilton County has reported 13,744 cases.