Atlanta, GA—Earlier this month, the CDC updated COVID-19 isolation and quarantine recommendations.

The new guidance calls for shorter isolation for asymptomatic and mildly ill people and quarantine periods of 5 days in order to focus on the period when a patient is most infectious. That is followed by continued masking for an additional 5 days.

Questions have been raised about why public health officials took that action, and the CDC responded to those concerns on its website.

"COVID-19 cases due to the Omicron variant have increased along with seasonal increases in influenza and other respiratory virus infections," the agency explains. "The potential for a large number of cases raises serious concerns about societal impact due to illness, as well as isolation and quarantine requirements. CDC has been monitoring the emerging science on when and for how long a person is maximally infectious with Omicron, as well as the effectiveness of COVID-19 vaccines and booster doses against Omicron infection. Data related to the mental health effects of the pandemic and adherence to prevention interventions have also been considered."

Specifically, the CDC states that data, which includes a review of 113 studies from 17 countries, suggest that the majority of SARS-CoV-2 transmission occurs early in the course of infection. "Infectiousness peaks around one day before symptom onset and declines within a week of symptom onset, with an average period of infectiousness and risk of transmission between 2-3 days before and 8 days after symptom onset," public health officials advise.

They caution that the data are from studies of prior SARS-CoV-2 variants, including Delta, adding, "The science is evolving, particularly for the Omicron variant, and some reports suggest that compared with previous variants, Omicron has a shorter incubation period (2-4 days), defined as the time between becoming infected and symptom onset."

The CDC notes that another factor in the decision was how the pandemic could affect society, explaining that the "spread of the Omicron variant has the potential to worsen staffing shortages and increase supply chain challenges, which jeopardize industry, education, and other systems that are essential to maintain a functioning society and economy. The pandemic has also had a negative impact on the mental health of adults in the United States, largely due to economic and social concerns."

Compliance also is a concern, with the CDC noting that, while many patients intend to self-isolate, actually doing so is challenging, especially when so many infections are asymptomatic. They added that studies suggested that only about 25% to 30% of people isolated for the full 10 days.

"These updated recommendations also facilitate individual social and well-being needs, return to work, and maintenance of critical infrastructure," public health officials add. "Preliminary data suggest that the Omicron variant is up to three times more infectious than the Delta variant. With the recommended shorter isolation and quarantine periods, it is critical that people continue to wear well-fitting masks and take additional precautions for 5 days after leaving isolation or quarantine."

The guidance emphasizes that "isolation should only end if a person has been fever-free for at least 24 hours without the use of fever-reducing medication and other symptoms have resolved."

CDC advises that modeling data from the United Kingdom reinforce the importance of mask use, pointing out that, after the 5th day of a positive test, an estimated 31% of persons remain infectious. They emphasized, "Mask use and layered prevention strategies, such as receiving all recommended vaccination and booster doses, physical distancing, screening testing, and improved ventilation, are key to preventing COVID-19 and decreasing transmission."

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