COVID-19 Data Dispatch

Tag: outbreaks

  • COVID source callout: Outbreak at a CDC conference

    Last week, we learned that a CDC conference—a gathering of experts in the agency’s epidemic intelligence service, no less—led to some COVID-19 cases, thanks to reporting by the Washington Post.

    Well, this past Tuesday, the Post published a follow-up story: more than 30 people got sick following the conference, and the CDC is working with the Georgia Department of Health to investigate. The case count was 35 as of Tuesday, and is surely higher now; about 2,000 people attended the conference.

    It’s now safe to say that this conference led to an outbreak. And that isn’t a surprising outcome, considering that it didn’t require masks or other COVID-19 safety measures. As I wrote last week, this outbreak basically signifies that the CDC considers ongoing COVID-19 spread at large events normal and unavoidable.

    Even though this situation is, in fact, disappointing and could have been avoided with basic safety measures. 🙃

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  • COVID source callout: Spread at a CDC conference

    This past week, the CDC hosted a conference of about 2,000 people in the agency’s epidemic intelligence service. It was the first time this conference was held in-person since the pandemic started, and it appeared to take place with fairly limited (if any) COVID-19 precautions.

    And at least a few of the conference’s attendees tested positive for COVID-19 afterward, according to reporting by Dan Diamond at the Washington Post. While a CDC spokesperson told Diamond that the cases are “reflective of general spread in the community” and “should not be referred to as an outbreak,” it’s obviously not a great look for the agency to have virus spread at a conference intended to celebrate progress over COVID-19.

    These cases—and the CDC’s communication around them—add to a growing pattern of downplaying continued coronavirus transmission. The CDC is essentially saying it’s normal to risk COVID-19 at any large event going forward, even if that event is run by people who should, theoretically, have a good understanding of how to keep its attendees safe.

    Epidemiologist Ellie Murray elaborates on this idea in a Twitter thread about the situation:

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  • COVID source shout-out: FERN’s mapping project shuts down

    COVID source shout-out: FERN’s mapping project shuts down

    Screenshot of the COVID-19 food system outbreak map, taken on September 4.

    In April 2020, Leah Douglas started tracking COVID-19 outbreaks at meatpacking plants, food processing facilities, and farms. Douglas is a reporter at the Food & Environment Reporting Network (FERN); she shared her findings through an interactive dashboard on the FERN website while also writing stories to illuminate the numbers.

    On September 2, Douglas announced that the project is shutting down—after counting almost 100,000 COVID-19 cases and 466 deaths among workers in the U.S. food system.

    “Initially, I imagined the project would produce a one-time visualization of the spread of the virus at food manufacturing plants last spring,” Douglas writes in a post announcing the project’s end.  “But it quickly became clear that the scope of worker illness, and the lack of information disclosure from companies and public health authorities, necessitated deeper investigation.”

    Douglas explains that, while the project was challenged from the start by a lack of data from food companies and public health agencies alike, data have become even scarcer in recent months. “There likely hasn’t been another surge like the one witnessed at meatpacking plants in the spring of 2020, but data constraints mean that the true toll of the pandemic on food system workers is unknown,” she says.

    Douglas’ project was cited by major news outlets, appeared on TV shows, used by research organizations, and utilized by policymakers to draw attention to COVID-19 outbreaks in the food system. It was also listed as one of the COVID-19 Data Dispatch’s best COVID-19 data stories of 2020.

    Here at the CDD, we thank Leah Douglas for her months of hard work on this incredibly important issue—and wish her the best in her new position at Reuters.

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  • A dispatch from Provincetown, Mass.

    A dispatch from Provincetown, Mass.

    Provincetown in June 2006. Source: ingawh via Wikimedia Commons

    Last week, a COVID-19 outbreak in Cape Code, Massachusetts was revealed to be the subject of a major CDC study providing evidence of the Delta variant’s ability to spread through vaccinated individuals. The outbreak quickly became the subject of national headlines, many of them sensationalizing Delta’s breakthrough potential—while failing to provide much context on the people who actually got sick.

    Here’s one big piece of context. Provincetown, the center of this outbreak, is one of America’s best-known gay communities, and the outbreak took place during Bear Week. Bear Week, for the uninitiated, is a week of parties for gay, bisexual, and otherwise men-loving men who identify as bears—a slang term implying a more masculine appearance, often facial and body hair.

    This week, I had the opportunity to talk to Mike, a Bear Week attendee from Pittsburgh who caught COVID-19 in Provincetown. (Mike asked me to use only his first name to protect his privacy.) He told me about his experience attending parties, getting sick, and learning about the scale of the outbreak.

    We also discussed how Provincetown and the Bear Week community were uniquely poised to identify this outbreak, thanks to a better-than-average local public health department and a group of men who were willing to share their health information with officials.

    The interview below has been lightly edited and condensed for clarity.

    Betsy Ladyzhets: My first question is just like, how are you doing? How have you been after being involved in this outbreak?

    Mike: I’m good… I live in Pittsburgh, I drove back on that Saturday [after the week of Provincetown events] and on Sunday, I started coughing really bad as I was driving home. This just came out of nowhere. I had to pull over, I’m like, yeah, I’m not good. This cough was a lot worse than I had anticipated. So, that was my first symptom. I went into the office Monday after getting home…  My first test was negative, on like Monday or Tuesday. But like, I’m still coughing. I didn’t fully trust it. So I got another one Friday, a PCR test.

    BL: So, you got tested twice? Did you experience contact tracing, or how did you get identified as part of the outbreak?

    M: I mean, I just knew I’d been there. Um, no one reached out but… There was a Facebook group, probably ten or fifteen thousand people in it. Lots of people posted about their test results. Like, people after they were leaving [Provincetown], started quarantining.

    The thing about Provincetown is, there were events that happened in the first week [of July, for July 4] that no one really had time to process… Then Bear Week, the week I went, I went at the busiest week of the year for the town. And it had to be, from a planning perspective, I don’t know that was necessarily the best time to have two huge events back to back.

    All the official events for the week that I went were canceled, though there were some of the regular bars and stuff doing events. There was, at the time, I think one venue that has a mostly outdoor party every day from like three to seven, that was very heavily attended with one or two thousand people every day, mostly outside and it’s possible to distance at. I only ended up going once or twice just because it wasn’t really where I wanted to be regardless of COVID risks, it wasn’t particularly a scene that I was craving at the time.

    I only went to, maybe, three or four indoor things the whole time, and it was without a mask for two or three of them. There’s a bunch of nightclubs in Provincetown that were still having events. And I don’t think that any of the bars themselves that were having events were requiring vaccination cards or anything. One venue that I saw a show at, they announced the next day that they were making either masks or proof of vaccination required. One of the venues that has outdoor events, they just moved all their shows outside instead of inside.

    BL: I see. And you mentioned the Facebook group, was that how you found out that a lot of people were getting tested and things like that?

    M: Yeah, there were somewhere between ten and fifteen thousand people in the group, planning this whole week. People usually come to Provincetown from all over, sometimes from abroad, though I don’t think there were many people coming from abroad this year because of the restrictions.

    BL: How did you learn about the big CDC study getting written about this?

    ML: I didn’t really have any idea until afterwards. There were lots of people in the group saying that Barnstable County, or the Massachusetts Department of Health, wanted to know—they wanted people to call if they’d gotten a positive test so they could keep better track of it. I mean, I think part of why the report was able to happen was that it was in a place with better respect for public health than, like, the state of Florida would have, if this kind of outbreak would’ve happened there.

    B: Yeah, I mean, it definitely seems like they responded quickly. Because I know they had, like, a 15% positivity rate one week, and then within a pretty short time it was back down.

    M: The town itself is a mostly gay, retirement-somewhat community. They can spend lots of money on other things [like public health]. They’re not necessarily spending money on schools because of how many people don’t have any kids around that they need to spend money on. And I mean, there are a lot of residents who live there year-round who tend to be older and are at more risk.

    So the week [Bear Week] itself is unique, and then there was a huge community presence about it, everyone wanted to be—for the most part, we’re comfortable about reporting afterwards. I don’t think anyone knew, walking into this, what it would lead to, but… there’s a feeling of community, and that ten thousand-ish Facebook group, I don’t think we otherwise would have necessary talked to each other or told each other about Massachusetts [public health department] asking people to call if they were positive.

    BL: And did you do that? Did you call them?

    M: Um, I personally didn’t, since I didn’t even find out I was positive until a few days later.

    BL: Now, as you know, this outbreak has gotten a lot of national coverage, it’s been kind of sensationalized, with a lot of people focusing on the vaccine breakthrough cases and stuff like that. I know you were not personally one of the people whose test measurements are included there. But what is that experience like of being part of this thing that has gotten so much national attention?

    M: I posted about it on social media and there were lots of people who were surprised or whatnot. I think, at least in my head, I went in with a calculated risk, of like 10, 20, 30, or more in the ten thousand-ish people coming, a lot of them are traveling on planes. I drove, thinking I’ll come into this place and I think I’ll make okay decisions…

    And there were people in this one place for a whole week, that I guess you were able to test from the CDC’s perspective. I don’t think there are many other places that are as remote as Provincetown where people are staying for the entire week, and everyone generally leaves on the same day, and everyone was in conversation with one another, talking about what happened.

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  • Your Thanksgiving could be a superspreading event

    Your Thanksgiving could be a superspreading event

    Between 10% and 20% of people infected with COVID-19 are responsible for 80% of the virus’ spread.

    You might have seen this statistic before, but take a second to think about what it means. Imagine that one unlucky person at a crowded restaurant, infected with the novel coronavirus but not yet symptomatic enough that she has noticed, spreads the virus to ten others. Meanwhile, her ten coworkers, who all contracted the virus at the same time as she did, do not spread the virus to anyone else at all. This type of dispersal—what epidemiologists call a large k value—introduces a level of randomness to COVID-19 spread which makes it difficult to track and protect against.

    But scientists are learning to better understand COVID-19 spread by keeping tabs on those instances where one person infects many, which they call superspreading events. While research continues about the underlying biology driving who is infectious and who isn’t, investigating the events in which people get infected can help us better understand how to protect ourselves and our communities.

    For more thorough explanations into the science of superspreading, I’d recommend you read Christie Aschwanden in Scientific American, Zeynep Tufekci in The Atlantic, or Martin Enserink, Kai Kupferschmidt, and Nirja Desai with an incredible series of scrolly visualizations in Science Mag.

    Here, I’m focusing on the data around these events: how we identify them, what the data tell us so far, and why we should keep them in mind as temperatures drop and cases rise.

    How do we find superspreading events?

    The CDC defines a superspreading event as one in which “a few persons infect a larger number of secondary persons with whom they have contact.” This leaves a lot of room for interpretation, as different researchers have different thresholds for determining how many people must be involved. Depending on who you talk to, anything from a 500-person rally to your extended family’s Fourth of July gathering might fit the definition.

    So, when you see a sensationalist article claiming that some event caused superspreading, it is important to consider what definition was being used and how the given event was identified as one that fits.

    There are three ways superspreading events can be identified:

    • Continuous tracking of an outbreak site: This is the easiest way to find superspreading. You have a place with a lot of people—say, a nursing home, a prison, a college campus—and you watch how many cases erupt over time. This may be an easier means of finding events because local administrations or public authorities are conducting regular testing and making data public; meanwhile, the sites themselves may have large groups of people living and working in close quarters, which is a prime environment for virus spread. Scientists count these sites as superspreading events even though they are not “events” in the way we usually think of the word because this type of long-term superspreading can have the biggest impact. California’s San Quentin State Prison, for example, was ordered to reduce its prison population after over 2,000 prisoners tested positive.
    • Contact tracing: This strategy, in which public health officials contact individuals who test positive and ask them about their contacts to find other infected individuals, has not taken off in the U.S. as it has in other countries, which makes it harder for us to identify superspreading events. It works like this: if contact tracers find that one new case is a teacher at an elementary school, for example, they can call other teachers and school administrators to find out which other cases are connected to that location. Japan has famously avoided widespread lockdowns by employing a “cluster-busting” strategy in which officials contact-trace backwards from new cases in order to find how those people got infected, then tell other people at the spreading events to isolate. Scientists in Europe and the U.S. are now promoting this approach as our cases surge.
    • Scientific studies: This strategy of superspreading identification is perhaps the least consistent, but it gets the most press. Epidemiologists may use publicly available case data, cell phone tracking data, or other information to look for patterns in new cases after major events. Such studies may draw attention, as a working paper on the Sturgis, South Dakota motorcycle rally did in September, but it can be difficult for scientists to investigate events when they don’t have access to data on precisely which cases are connected and how. The Sturgis paper was criticized for making estimates based on unreliable data. A similar new paper on the COVID-19 impact of Trump rallies is currently undergoing peer review.

    Where do superspreading events happen?

    Full-screen dashboard link.

    Independent researcher Koen Swinkels started a database to answer this question. The database is compiled from media reports, scientific papers, and public health dashboards, as well as volunteer reports. (You can submit an event through a form on the database’s site.)

    As of November 7, the database includes about 1,600 superspreading events, ranging from churches to dinner parties to meat processing plants. About 1,100 of these events took place in the U.S. For those American events, the most common superspreading settings by far are prisons (50,000 cases), rehabilitation/medical centers (27,000 cases), nursing homes (26,700 cases), meat processing plants (13,900 cases), and other medical centers (12,200 cases). Parts of the Northeast, West Coast, and South are heavily represented in the database, while other areas of the country have yet to see significant superspreading events logged.

    You can explore the map pictured above, as well as a bar chart which organizes superspreading settings by their COVID-19 case numbers, in a pair of interactive Tableau visualizations which I built based on this database.

    Swinkels emphasized in an email to me that the database is not at all representative of all COVID-19 superspreading events which have taken place, in America or around the world. “Hundreds of millions of people have been infected with SARS-CoV-2, while we have only about 200,000 cases linked to the 1,600 superspreading events in our database,” he said.

    He and other members of the team, including professors at the London School of Hygiene and Tropical Medicine, are currently compiling events from the most easily available public sources, which he admits is not a comprehensive strategy. Swinkels also noted that the events identified by public sources may be biased by where public health officials direct their focus, which can lead to settings that were closed in the spring or are now operating under restrictions being left out of this database and of superspreading research more broadly. The database is also biased by the team’s English-language familiarity; they are looking to find more events described in non-English language publications.

    What does this mean for the holidays?

    This newsletter topic was inspired by a reader question I got last week: Ross asked me how post-election gatherings and holiday celebrations might contribute to COVID-19 spikes.

    The evidence so far suggests that protests have not yet been a major cause of COVID-19 spikes. But “so far” is doing a lot of work in that sentence. While protests are generally outside and see high mask compliance, Swinkels explained, they tend to involve talking and singing in close contact, and instances of transportation and socialization around a protest might pose more risk. (Imagine, for example, shouting “FUCK TRUMP!” in a crowd of 500 with two friends, going to an outdoor bar together afterward, then each taking the bus home to three different parts of the city. That’s a lot of risk for one evening.)

    More research on protests is necessary to truly determine how much risk they might pose to the communities around them. And, as contact tracing apparatuses in different parts of the country scale up—slowly but surely—such research will get easier.

    Holiday celebrations, on the other hand, are a definitive cause for concern. These celebrations almost always occur indoors, involve talking and eating, and bring people together from disparate locations. Superspreader events also almost always occur indoors, may involve loud talking, and expand COVID-19 risk from one area to another. There’s a reason that Dr. Anthony Fauci’s daughters are not traveling home for Thanksgiving.

    I asked Koen what he’d learned from compiling and comparing hundreds of superspreader events. “Knowing more about where and when superspreading events occur can help you to avoid high-risk situations and live more freely in low-risk situations,” he said. He listed several key risk factors: indoors, poor ventilation, many people, close together, prolonged periods, loud vocalization (such as singing or shouting), and cold, dry air.

    He also highlighted the importance of understanding aerosol transmission. The six feet rule we’ve all come to know and flaunt is based on the dispersal of larger air particles, which don’t travel far from an infected person. But aerosols, which are smaller particles, are able to travel further and stay in the air longer—especially in indoor, poorly ventilated spaces. You can sit all the way across the room from Grandma while you eat, but if masks are off and all the windows are closed, it won’t make much difference. This FAQ document by aerosol scientists provides much more detail about how this type of COVID-19 spread works.

    I’m not going to tell you to avoid traveling for the holidays; I’m not a public health expert, I don’t have that authority. But I can give you this fact: your Thanksgiving could be a superspreading event. So could the train you take to get to your relatives’ house. So could the bar where you go for outdoor drinks a few days before traveling. In order to make it through this winter, we must all be aware of our risks and adjust our behavior accordingly.