Last week, coronavirus cases reached an all-time high in the US, allowing the national count to clear 500,000.
In light of this, some counties have decided to reinitiate commercial restrictions and lockdown mandates.
Although hospitalizations and death rates appear to be on the decline, reducing transmissions among vulnerable communities is particularly important ahead of winter and a string of super-spreader holidays.
The U.S. Centers for Disease Control and Prevention recently revised its guidelines in relation to SARS-CoV-2 exposure. Initially, a high-risk interaction was defined as one that exceeds 15 consecutive minutes and a distance of six feet between a subject and a carrier who has been infectious for at least 24 hours.
Now researchers are saying that even exposure-time achieved cumulatively poses a substantial risk for a subject.
In some instances, transmission can even occur in less than a minute. It all depends on the initial viral dose one is exposed to.
“Contact tracers use clear protocols to notify, interview, and advise close contacts to patients with confirmed or probable COVID-19. Jurisdictions can use the following steps and considerations as a framework when developing a protocol for the tracing of close contacts,” the agency wrote on their website. “A close contact to a patient with confirmed or probable COVID-19 should be notified of their exposure as soon as possible (within 24 hours of contact elicitation). The patient may elect to notify some or all of their close contacts before the contact tracer.”
The empirical re-assessment tailed data from a Vermont corrections officer who contracted SARS-CoV-2 after multiple short visits with inmates who had previously tested positive for the virus.
During these visits, the officer got within 6 feet of the infected inmates at least 22 times over an eight-hour shift. His collective exposure time was only 17 minutes and he wore a mask on every occasion yet transmission was successful.
This scenario actually attends many positive cases–more usually on the back of asymptomatic carriers. Not too long ago, a bride who contracted a symptomless presentation of COVID-19 ended up contributing to an outbreak in Louisville. Positive cases occurred after attendees of the wedding spent a few minutes interacting with the bride here and there over the course of the evening.
The science is simple enough even if some of the exact determinants are still unknown. In order for a close-contact to become ill from a carrier, they have to be exposed to a sufficient number of viral particles. The initial dose one is exposed to is called the viral inoculum.
The higher the viral inoculum the higher the expected viral load. The higher the viral load the higher the likelihood of transmission.
The CDC ranks high-risk contacts as the following:
- Hospitalized patients
- Healthcare personnel (HCP)
- First responders (e.g., EMS, law enforcement, firefighters)
- Individuals living, working, or visiting acute care, skilled nursing, mental health, and long-term care facilities
- Individuals living, working, or visiting community congregate settings (e.g., correctional facilities, homeless shelters, educational institutions, mass gatherings, and workplaces including production plants)
- Member of a large household living in close quarters
- Individuals who live in households with a higher risk individual or who provide care in a household with a higher risk individual (Note: Household members who likely had extensive contact with a patient with COVID-19 should constitute the highest risk close contacts.