New York State disease detectives, preparing to launch an unprecedented program to identify those infected with coronavirus, will be on the lookout for “superspreaders” who transmit the virus at an above-average rate, experts say.
Once an infected person is identified, contact tracers will investigate how the infection happened and alert the patient’s circle of contacts, with information collected on apps and fed into state databases to help New York’s virus-fighting strategy.
“So-called ‘super-spreading events’ involve transmission from one individual to many others,” said Dr. Adam Karpati, senior vice president of public health programs for Vital Strategies, a group funded by Bloomberg Philanthropies that is working with the state effort. “What we’re seeing is that a majority of infections are associated with a smaller number of individuals. But we do need to learn more.”
State health officials expect to hire as many as 17,000 contact tracers — disease investigators who will find out who has come in contact recently with a person testing positive for the virus and isolate them to prevent disease spread.
For medical investigators, one of the most intriguing riddles is trying to find out why certain infected people, for an unknown reason, spread the virus at an alarmingly high rate. So far, nearly 20,000 New Yorkers have died from COVID-19, the disease caused by the virus spread.
“There is something distinctive about these people,” said Dr. William Schaffner, the medical director of the National Foundation for Infectious Diseases and a professor in the division of infectious diseases at Vanderbilt University Medical Center. He said the average person contracting COVID-19 would generally infect about three people, while a superspreader could infect about 10.
“Everyone who is infected doesn’t have the same capacity to spread as others,” said Schaffner, who has witnessed superspreading with other respiratory diseases such as tuberculosis and SARS. “They shed [the virus], for reasons not understood, with a frequency more than the average person.”
Schaffner said medical experts are still not sure if superspreaders have a unique immune system or genetic makeup or just happen to be in circumstances that allow them to spread the virus at an above-normal rate. Through contact tracing, he said, researchers may be able to investigate other major telltale questions, such as whether “superspreaders” are “asymptomatic” — showing no obvious symptoms like fever or dry cough — and whether or not they get sick quicker than most patients.
“Testing and contact tracing will help us find out clusters and define a COVID superspreader more precisely,” Schaffner said.
The need to halt “superspreading events” is underlined in a June 2020 article in the journal “Emerging Infectious Diseases,” available on the federal Centers for Disease Control and Prevention website. Its co-authors, Drs. Thomas R. Frieden and Christopher T. Lee, both work for Resolve to Save Lives, a Bloomberg-funded health unit working on the state’s contact tracing program
“Although we still have limited information on the epidemiology of this virus, there have been multiple reports of superspreading events (SSEs), which are associated with both explosive growth early in an outbreak and sustained transmission in later stages,” warn Frieden, a former CDC chief, and Lee. “To prevent and control SSEs, speed is essential.”
In the article, they underline the need for “rapid identification, diagnosis and isolation” of infected patients. Places that are “high risk” for superspreader outbreaks, they said, include health care facilities, nursing homes, prisons, homeless shelters and schools.
Frieden and Lee cite contemporary examples from China and South Korea, as well as the highly contagious spread aboard the Diamond Princess cruise ship in February, where passengers had to be quarantined in Japan for a month. They also mention the early 20th-century New York case of Mary Mallon, a cook later known as “Typhoid Mary,” who was an asymptomatic typhoid carrier infecting more than 50 persons, including while working in Oyster Bay, Long Island.
Experts say New York’s attempts to control the virus through contact tracing may only be effective if patients cooperate quickly in following social distancing measures once they know they’ve been infected. As Freiden and Lee conclude, “Effective case isolation and contact tracing might be sufficient to control a cluster of COVID-19, but the probability of control will decrease with delays in patient isolation from symptom onset.”
The New York contact tracing program, headed by Bloomberg and the Johns Hopkins Bloomberg School of Public Health, calls for 30 tracers for every 100,000 individuals. Some will be recruited from local government agencies and others hired from the outside.
Potential tracers are expected to start in the next few weeks once they are trained. Once hired, tracers will work for a year.
Future virus patients who test positive — based on diagnostic tests already used to confirm cases in New York — will be interviewed about their contacts during the previous 14 days. Tracers will then contact those in this circle of contacts and instruct them to quarantine or isolate themselves for two weeks to avoid spread of the virus. Smartphone apps are being developed by Bloomberg’s Vital Strategies for this effort, including one that will allow those in quarantine to report any symptoms they may be suffering.
Health experts say good contact tracers, along with their technical training, need to have strong empathy for the plight of infected patients being asked many personal questions. Last week, the CDC updated its training guidelines, suggesting that qualities needed for contact tracers include “motivational interviewing skills,” “cultural sensitivity” and “risk communication skills.”