Transmission Rates and Social Distancing

By Dr. Landon Opunui, ND

Dr. Opunui is the Medical Director of Na Puʻuwai, the Native Hawaiian Health Care System serving the communities of Molokai and Lanai. He and the staff of Na Puʻuwai will be regularly contributing to an ongoing health column in The Molokai Dispatch.

As the COVID-19 pandemic continues to evolve, the good news is that it does not appear to look nearly as catastrophic as once believed. The numbers of new cases and deaths both nationally and locally appear to be either plateauing or declining. To date, Molokai remains at two cases islandwide, with no indication of community spread.

The public health dilemma is now shifting to whether we continue to quarantine to stop the virus from further spreading or begin the process of opening up parts of our daily routines to return to something resembling “normal.”

Predictions with population-based models are challenging because of key assumptions that need to be made about the accuracy of transmission and fatality rates. Even the most subtle projection errors, such as a transmission rate of 2.3 versus 2.4, triple the projected number of infected people from 10 million to 30 million.

The accuracy challenges stem from an imperfect data set. For example, case rates (CR) — the number of confirmed COVID-19 positive patients — can be known, while infection rates (IR) — the percentage of all individuals, known and unknown, who have the virus — is next to impossible to know without widespread testing. Case rates of coronavirus are an underestimation of infection rates, which are going to heavily impact the accuracy of fatality rate predictions.

Aggressive social distancing and the closure of all nonessential business have changed conditions dramatically. Assumptions had to be made for these models to function and we are actually fortunate these projections have been wrong thus far.

As a result, COVID-19 cases and fatalities across the nation will likely be in line with one of the worst influenza seasons and not the previously predicted millions.

If our predictions were wrong because we misunderstood the biology of the virus, then when should we begin the thoughtful reopening of life and the economy? However, if our predictions were wrong because social distancing measures were powerfully effective, then we need to maintain our vigilance with strict social distancing until successful treatment measures become available.

One of the important data sets that will help us more confidently answer these questions is populationwide testing to include asymptomatic individuals so that we can more confidently estimate the true infection fatality rate of COVID-19, which is predicted as 0.1-0.26 percent.

As difficult as the decision was, Mayor Michael Victorino and Gov. David Ige likely made the right decision to extend the stay-at-home order through the month of May. During this extended timeout, we should wisely take the opportunity to better understand our opponent by offering more widespread community testing such as the free testing offered on Molokai through the Hawaii Crisis Healthcare Alliance on April 7.