By DAN STONE, MD (8)

Woody Allen once commented that life is composed of the horrible and the miserable, with the latter offering merely lesser calamity.  The COVID epidemic seems to be following “Allen’s Law” as its course diverges in different localities.   Current evidence suggests that measures taken by California and Los Angeles civic authorities as well as by residents and health care providers succeeded in “flattening the curve” and are leading LA toward a merely “miserable” epidemic like Korea’s rather than an explosion like New York’s or Italy’s.  Local epidemiologists have been slow to draw conclusions from the emerging data, perhaps out of concern that even a hint optimism on the last few weeks’ battle might lead the public to believe the war is over when it still just beginning.       

With extensive testing limited by a shortage of test kits, tracking the epidemic requires extrapolation from the number of hospitalizations and deaths.    This week LA’s largest medical center continued to see a stable census of COVID-19 patients at a time that they “should” have been skyrocketing were LA headed for a New York style surge.  We now understand that the typical incubation period for COVID-19– the time from exposure to onset of illness — is about five days and the typical time from exposure to hospitalization, when it occurs, is about twelve.  So, hospitalizations provide insights into COVID transmission about two weeks prior.   The stability over that period confirms the success of the lockdown.  In the three weeks since the state’s lockdown order there have been no athletic events, no movies and no crowds at restaurants nor malls.  So, there were markedly fewer opportunities for person to person spread. 

Additionally, the stability of the epidemic in LA should persist while social distancing remains in place.  As those less compliant with social distancing become progressively infected, the remaining pool of the uninfected is increasing composed of people more attentive to risk and less prone to future infection.  In addition, with the new requirement to use face masks in public, increasing civic policing of public venues and with health systems’ improved ability to protect healthcare workers and non-COVID patients from infection, the future risk should trend downward.  Perhaps the main risk of a break-out would be new infections occurring in populations that have been relatively isolated but  lack the ability to practice individual social isolation.  This would include nursing home patients, prison inmates and the homeless.  However, in a metropolitan area of thirteen million, these populations are probably not large enough to impact the overall course of the epidemic in LA. 

Why has COVID-19 in LA progressed so differently than same disease in New York?    The answer may relate to New York’s population density and the challenge it poses to social distancing.  New Yorkers struggle to maintain social distance in high-rise elevators, subways and in crowded stores and sidewalks.   Compared to New Yorkers, Angelinos practice social distancing during normal times.  The city’s  neighborhoods of single-family homes and smaller apartment buildings and its “car culture” also may help.   The important adaptation to “working from home” likely was probably easier here as the practice was already widespread to avoid long commutes.   In addition, the lockdown order occurred early enough in the course of the epidemic that the city probably never reached the “critical mass” of cases that would overwhelm the effects of social distancing.

The success of social distancing measures in LA means that emergency departments and ICUs will not be overwhelmed and forced to ration care.  Uninfected individuals who remain susceptible may benefit from future improvements in care.   However, the city’s success leaves it with a miserable problem: millions of susceptible individuals remain in lockdown.  If released to resume their usual activities even a relatively small residual number of infected individuals would likely serve as the embers to re-kindle the epidemic, creating the calamity we have worked so hard to avoid.  The 1918 flu epidemic offers a century old lesson on this risk.  About half of major cities noted a second peak of infections when restrictions were rescinded.  Some, like Denver, St. Louis and Kansas City experienced second peaks that were even deadlier than the first.  

The hard reality is that there are only three ways for the epidemic to end:  vaccination, curative treatment and herd immunity from the survivors of infection.   As vaccination and curative treatment could be a year or more away, the most practical current approach is a controlled release of susceptibles from social distancing in a way that minimizes their risk and avoids a surge that could overwhelm healthcare facilities.  If progress continues, public health authorities eventually could allow a rolling release starting with the lowest risk cohorts such as those between ages 20 and 25.   Another early release cohort would be individuals who contracted COVID and are now immune.  The first serology testing for immune antibodies recently started.  If ramped up quickly, these tests could soon identify millions of individuals now safe to return to their normal activities  Gradual release by risk cohort would modulate the numbers of infected and allow the volume of illness to be adjusted to the throughput of emergency departments and ICUs.  The process would expose the least vulnerable while allowing the oldest and sickest among us wait for the development of a vaccine or definitive treatments that may be a year or more in the future.

One of my colleagues recently noted that release by cohort would expose millions to the virus and could produce thousands of deaths that might be averted by waiting for a vaccine.  Unfortunately, the millions at low risk simply cannot put their lives on hold for the many months needed for a vaccine.  The possibility also remains that an effective vaccine may not be feasible or may take longer than expected to develop.  The U.S. faced a similar situation in the Pacific during World War II.  The strategy of “island hopping” cost thousands of deaths that might have been averted had we waited for the development of the atom bomb.  Unfortunately, the timing and practicality of the bomb, like a corona virus vaccine, was uncertain.  The high stakes of a war or an epidemic mean that parallel strategies must be pursued, even at great risk and high cost.  

For now, the next steps to fight the epidemic in LA and elsewhere remain clear.  Above all, people must stay the course on social distancing and other public health mandates.  Compliance saves lives and optimizes the strategic deployment of scarce healthcare resources.   The current LA success story, paired with a cautious and effective release strategy, can offer hope and a path forward for those in New Orleans, Detroit and other areas where the epidemic is still escalating.