Washington Covid-19 outbreak: New variants flout old ‘close contact’ rule

House Speaker Nancy Pelosi, Senators Susan Collins and Raphael Warnock, and Representative Peter DeFazio have announced this week that they have tested positive.

Health experts say the outbreak may be rooted, in part, in outdated and confusing guidelines from the US Centers for Disease Control and Prevention that help people assess their risk of contracting the virus. that causes covid-19 or transmit it to others.

On Thursday, after announcing that she had been in close contact with someone who had tested positive for COVID-19, Vice President Kamala Harris presided over the Senate confirmation of Ketanji Brown Jackson without wearing a mask, even though CDC guidelines recommend wearing a mask near from other people for at least 10 days after exposure to the virus.

On the same day, at a World Health Day press event, Xavier Becerra, secretary of the US Department of Health and Human Services, explained that both he and the director general of the World Health Organization, Tedros Adhanom Ghebreysesus, would wear masks at the event: except as he speaks, “because every single one of us has been around someone who recently tested positive.”

Health experts said Friday that Americans trust the CDC’s guidance that is overdue for an update.

Origins of the 6 foot rule

Since the early days of the pandemic, the CDC has defined someone who is a “close contact” (and therefore at risk of contracting and spreading the virus) as someone who has spent a cumulative total of at least 15 minutes within 6 feet of another person who has laboratory-confirmed Covid-19 or who has been told by a doctor that they have Covid-19.

With newer, more contagious variants like BA.2, Kimberly Prather, an aerosol scientist at the Scripps Institution of Oceanography, said the rule needs to be rethought.

“Fifteen minutes and 6 feet wasn’t really helpful in the first place,” he said. “We know that people get infected in less time and at a greater distance.”

Prather believes that the rule for close contact should have been based on everyone sharing the air in a room for a certain number of minutes.

Distance, specifically the distance of 6 feet, has been in the infection equation since the late 1800s, when a scientist named Carl Flugge discovered that infections could be transmitted via airborne respiratory droplets. He recommended separating people to prevent contagion. Scientists tested it using glass plates and got as far as 6 feet.

In the 1930s, another scientist, William F. Wells, discovered that although some droplets from the mouth or nose are large and fall to the ground quickly (within 3 to 6 feet), sick people can also shed viruses More smalls. filled aerosols that float in the air for minutes or even hours. Those can also be infectious.

Evidence of airborne spread

Since March 2020, when 52 members of a choir in Skagit County, Washington, contracted COVID-19 after attending practice with only one sick person, health officials have known that the virus that causes COVID -19 can be transmitted through smaller aerosols. making distance less important than ventilation and time.

However, the CDC continues to factor 6 feet into its risk equations.

In response to a question from CNN, a CDC spokesperson said Thursday that the agency did not plan to change the definition of close contact “at this time.”

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“If you were part of an event where there are multiple infections, you will have been exposed. I don’t care if it’s 6 feet or 15,” said Dr. Carlos Del Rio, an infectious disease specialist at Emory University.

If you are exposed but are up to date on your vaccinations, Del Rio said, you should watch for symptoms and wear a mask for 10 days, which is what the CDC says as well.

“If I was in that room with Pelosi and others where they got infected, I would consider myself a close contact because I was there,” he said. It’s not known exactly where Pelosi got infected, but he was among lawmakers who appeared maskless with President Biden at a signing ceremony on Wednesday. Under CDC guidelines, Pelosi was not considered to be a close contact of the president, the White House said in a statement.

That is closer to the way other countries have defined exposure.

Until February, when the UK began rolling back its pandemic restrictions, health authorities defined close contact more broadly. His definition included anyone who:

  • Live with someone who tests positive
  • You have face-to-face contact or a conversation within about 3 feet of someone who has tested positive
  • Has been within 3 feet for 1 minute or more, regardless of whether the contact was face-to-face
  • You have spent more than 15 minutes within 6 feet of someone who has tested positive
  • Have traveled in the same vehicle or plane with a positive case

More convenience than science

Linsey Marr, a professor of civil and environmental engineering at Virginia Tech who studies aerosols, said the CDC needs to review its contact precautions.

“I think they should update it, because I think it’s based on outdated thinking about streaming,” he said.

Marr said the CDC likely made the 6-foot, 15-minute limits to try to make the best use of limited public health resources, such as contract tracing.

“It’s based more on convenience than science at the moment,” he said.

Marr said that all superspreading events have four things in common: a lot of talking, shouting, or singing; long exposure times; poor ventilation; and without masks.

“If you have that kind of situation, then I would say everyone in the room is potentially exposed,” he said.

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