Ask Dr. Halverson: COVID-19 clusters and super spreaders

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By Dr. Jim Halverson
There has been a significant increase in the number of COVID-19 cases in the Ojai Valley recently. Between Aug. 13 and Aug. 27, 54 cases were reported (22 in Ojai and 32 in Oak View).
As reported by the Ojai Valley News on Aug. 28, nearly all of these cases occurred at two local nursing homes, Ojai Health and Rehabilitation, in Ojai, and Wellness Care Senior Living, in Oak View. These outbreaks are examples of what very typically occurs with the SARS-COV-2 virus. Because it is a very contagious virus, cases often occur in clusters, and are frequently caused by superspreaders.
The World Health Organization uses the following categories to define the types of transmission that occur in diseases — sporadic, community spread, and cluster cases. Sporadic diseases are defined as occurring only occasionally and usually without geographic concentration, such as tetanus or rabies.
Community cases are when a disease is transmitted and the people with the disease did not have any contact with a person from a known hot spot of the disease, which early on for this disease was China, then areas in Western Europe. 
A cluster is defined as an aggregation of cases of a disease closely grouped in time and space.
There have been many reported COVID-19 clusters. In Washington state on March 10, one person at a choir practice infected 52 other attendees. Two ultimately died. Additional clusters have occurred many times in group settings at churches, weddings, bars, restaurants, colleges, nursing homes and other gatherings. Public health officials consider clusters an emergency and move in rapidly to quarantine, test and retest all individuals who were in attendance at these gatherings or who live or work at these facilities. In many of these cases, public health investigations have determined that one person, called a superspreader for tracing purposes, was the source of the cases.
Although we can’t medically diagnose superspreaders, we can still limit their impact. Contact tracing is critical for identifying the potential carriers and isolating them and the people they have been in contact with. This keeps them from further spreading the virus. Epidemiologists believe that 10 to 20 percent of people with COVID-19 are responsible for about 80 percent of the cases. 
Aerosol spread of the virus is likely the cause of many of these events, a topic I will discuss in my article in next Friday’s Ojai Valley News. They also point out the importance of mitigating the THREE C’s of transmission for COVID-19: CLOSED spaces with poor ventilation, CROWDED settings, and CLOSE contact with others. 
That means encouraging outdoor seating whenever possible and maximizing ventilation. In any indoor setting, limit the number of people in any room or building and continue to keep people spaced apart by at least 6 feet.
With Labor Day this weekend, please remember the following: COVID-19 is a party crasher. It appears to spread very efficiently from people who don’t yet have symptoms (and may not) or who are mildly ill. Research has shown repeatedly over the past several months that up to 40% of coronavirus transmission is taking place BEFORE a person shows symptoms. In fact, people are often the most contagious with the highest viral loads the day or two before symptoms begin. When an asymptomatic person with a high viral load walks into a crowded place — one with poor ventilation and where people are not wearing masks or social distancing — that is a recipe for a superspreading cocktail.
Stay 6 feet apart. Stay committed. Stay positive. Stay informed. Stay safe. Stay well.

— Dr. Jim Halverson is a longtime Ojai physician who writes a weekly column on COVID-19 for the Ojai Valley News.