What do we know about superspreader events in the pandemic?

KIM: WELL, DEBORAH, DOCTORS SAY, AS WITH ANY INFECTIOUS DISEASE, CERTAIN PEOPLE ARE MORE OR LESS LIKELY TO CONTRACT COVID, BASED ON A NUMBER OF FACTORS, AND THEY’RE STARTING TO NARROW DOWN WHO THOSE GROUPS ARE. ONLY A QUARTER OF PEOPLE LIVING IN THE SAME HOUSE HOLD AS COVID PATIENTS WILL ALSO GET INFECTED, EITHER BECAUSE THEIR EXPOSURE IS LOWER OR THEY HAVE T-CELL IMMUNITY. DR. ADALJA: THAT T CELL IMMUNITY MIGHT ARISE, BECAUSE THERE ARE FOUR OTHER CORONAVIRUSES THAT CAUSE ABOUT 25% OF OUR COMMON COLDS, AND SOME OF THAT T-CELL IMMUNITY MIGHT BE CROSS REACTIVE. KIM: THERE IS ALSO SOME EVIDENCE EMERGING THAT BLOOD TYPE PLAYS A ROLE IN CONTRACTING THE DISEASE. DR. ADALJA SAYS, THOUGH NOT CONCLUSIVE, RESEARCHERS ARE FINDING THAT PEOPLE WITH TYPE O BLOOD ARE LESS LIKELY TO GET COVID OR HAVE A SEVERE CASE. DR. ADALJA: WE DO KNOW THAT THE IMMUNE SYSTEM IS INTRICATELY INVOLVED WITH BLOOD TYPE, AND THERE LIKELY IS SOME DIFFERENCE THERE, BECAUSE WHEN PEOPLE HAVE TYPE O BLOOD, THEY HAVE ANTIBODIES AGAINST TYPE A AND TYPE B. THAT MAY PLAY SOME ROLE IN HOW THE VIRUS INTERACTS WITH THE RECEPTORS THAT IT HAS TO BIND TO KIM: RESEARCHERS ARE ALSO LOOKING AT VIRAL LOAD. GENERALLY THE HIGHER THE VIRAL LOAD, THE MORE SEVERE AND MORE CONTAGIOUS YOU MAY BE TO OTHERS, AND THAT IS WHY IT IS ESPECIALLY IMPORTANT TO WEAR A MASK. DR. ADALJA: BECAUSE IF YOU GET INFECTED DESPITE A FACE COVERING YOU’RE PROBABLY GETTING INFECTED , WITH A LOWER VIRAL LOAD, BECAUSE SOME OF THOSE PARTICLES ARE GETTING BLOCKED.

What do we know about superspreader events in the pandemic?We're still learning, but it seems that much of the spread of the coronavirus has been caused by what disease trackers call superspreader events.That’s when a single person infects a large number of other people, or when a gathering is linked to a large number of cases.There's no rule for when a cluster of cases is big enough to be called a superspreader event. But these are not instances of spread within one household. Instead, these are large clusters of cases where infection occurs in settings such as churches, restaurants or bars.In the United States, for instance, a choir member with symptoms attended a rehearsal in March. Of 60 others who attended, 52 got sick with COVID-19, including two who died.In Hong Kong, an outbreak at four bars infected 39 customers, 20 staff members and 14 musicians before ballooning further to infect 33 family members and other contacts. Disease trackers discovered that bands played at all four bars, so musicians may have spread the virus to more than 100 people all told.Scientists studying three months of contact tracing data from Hong Kong estimated that 19% of people infected were responsible for 80% of the spread of coronavirus infections.To prevent superspreader events, we need to better understand them, said Anne Rimoin, an infectious diseases expert at the University of California, Los Angeles.She has called for detailed contact tracing of the infections around President Donald Trump, including those who attended a Sept. 26 Rose Garden ceremony and indoor White House reception for Supreme Court nominee Judge Amy Coney Barrett.The timing of the event and the number of people infected suggests the possibility of superspreading, she said.“Contact tracing is the way you get to the bottom of a superspreader event,” Rimoin said. “That’s how you break chains of transmission.”Unlike many contact tracing investigations, where it can be difficult to find everybody involved, the White House investigation would have “exquisite records and video about who was where and when," Rimoin said. "It's an opportunity to learn about superspreader events that could save thousands of lives, if not millions of lives, in the long run.”

What do we know about superspreader events in the pandemic?

We're still learning, but it seems that much of the spread of the coronavirus has been caused by what disease trackers call superspreader events.

That’s when a single person infects a large number of other people, or when a gathering is linked to a large number of cases.

There's no rule for when a cluster of cases is big enough to be called a superspreader event. But these are not instances of spread within one household. Instead, these are large clusters of cases where infection occurs in settings such as churches, restaurants or bars.

In the United States, for instance, a choir member with symptoms attended a rehearsal in March. Of 60 others who attended, 52 got sick with COVID-19, including two who died.

In Hong Kong, an outbreak at four bars infected 39 customers, 20 staff members and 14 musicians before ballooning further to infect 33 family members and other contacts. Disease trackers discovered that bands played at all four bars, so musicians may have spread the virus to more than 100 people all told.

Scientists studying three months of contact tracing data from Hong Kong estimated that 19% of people infected were responsible for 80% of the spread of coronavirus infections.

To prevent superspreader events, we need to better understand them, said Anne Rimoin, an infectious diseases expert at the University of California, Los Angeles.

She has called for detailed contact tracing of the infections around President Donald Trump, including those who attended a Sept. 26 Rose Garden ceremony and indoor White House reception for Supreme Court nominee Judge Amy Coney Barrett.

The timing of the event and the number of people infected suggests the possibility of superspreading, she said.

“Contact tracing is the way you get to the bottom of a superspreader event,” Rimoin said. “That’s how you break chains of transmission.”

Unlike many contact tracing investigations, where it can be difficult to find everybody involved, the White House investigation would have “exquisite records and video about who was where and when," Rimoin said. "It's an opportunity to learn about superspreader events that could save thousands of lives, if not millions of lives, in the long run.”

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