The coronavirus recently named COVID-19 has exited China and created local outbreaks in South Korea, Israel, Iran and Italy. Many experts believe that it will soon cross the ocean and establish in a city in America if it has not already done so. I agree.
What will be the scenario, if COVID-19 enters a U.S. city like Memphis? To understand this, we need to get beyond denial, fear and misinformation and extrapolate using evidence-based modeling.
The early studies from Wuhan, China, from the initial 1,099 cases tell us that over 25% of infected patients are ill enough to require hospitalization and 1-2% may die.
Epidemiological assumptions are that one person with the virus infects three others and the number of cases doubles every seven days. And epidemiological science tells us that in an epidemic such as COVID-19 the actual number of cases may be much greater than the ones that are identified.
Overall, epidemics are not easy to predict and COVID-19 is no exception, yet respiratory viral illnesses follow a classic epidemic model:
Week 1: Index case
Like all epidemics from a single source, the COVID-19 virus will follow a well established bell-shaped curve. Just like a match in dry kindling creates a bushfire, an index patient in a susceptible population initiates an epidemic, followed by a steep rise in the number of cases until a peak is reached and then a fall in the number of new cases over time. Without doubt, COVID-19 will follow this trajectory in every city it impacts or multiple clusters in a given city.
Week 4: First case identified
Likely, four weeks or more after the initial case (often not identified), the first identified case of locally transmitted COVID-19 virus will be found by the health authorities through testing of a critically ill patient or through routine surveillance. By this time, it is likely, the virus has been locally established, with over 25 to 50 cases present in the community.
Week 6: First death
Much like an iceberg, the first death is only the tip of the COVID-19 cases. By week 8, one can anticipate four deaths, 100 hospitalizations, 120 identified cases, 200 physician visits and possibly 400 total cases in the city.
Epidemic if no interventions
The question remains: How long will the number of cases continue to rise in the early part of the epidemic? If no interventions are done by three months, there may be as many as 6,400 cases with nearly 2,000 identified cases, 3,200 visits to doctors, some 1,600 hospitalizations and possibly 64 deaths locally from the local spread of the infection.
Impact of intervention:
The epidemic curve can change with aggressive infection control measures. We know that interventions such as quarantine and a ban on large gatherings can reduce transmission.
Closing of schools, and working from home allows for social distancing, reducing the spread of infection in large populations.
And personal hygiene following the mnemonic WASH can reduce infection further: W for washing hands, A for avoiding touching face and surfaces, S for sneeze and cough covering, and H for home-rest when ill.
Even with the above measures, it is hard to predict when a decline in cases would occur. Much depends on whether the susceptible population is reduced significantly so that there are fewer vulnerable cases and the epidemic burns out. Or if an antiviral medicine or a vaccine is developed and deployed, then this can stop the epidemic.
Also, the impact of the seasons on COVID-19 is unclear. Flu declines in the summer season, as does SARS, but not other viruses like MERS.
While for many, COVID-19 infection will be mild or moderate, no different than the common cold, the greatest impact will be felt by the elderly. They are the most vulnerable to a severe respiratory infection and most likely to die from the virus. Early studies show that 80% of COVID-19 deaths were among those over 60 years of age and 75% of patients had comorbidities such as heart disease, diabetes or lung disease.
From our past learning and scientific extrapolation, as a nation and a city we do not want to be caught by surprise. We need to prepare for the worst and hope for the best.
Source: Daily Memphian