Thinking of a vacation get-together? Take a look at this disturbing map first

Don’t harass, but if you are planning on seeing family for the holidays i need you to take a look at this map. This is a color-coded guide to Covid-19 risk level, sorted by geography (at US county level) and crowd size. First, you choose the location where the gathering will take place. Then on the left you can choose an event size with the slider, from 10 to 5,000 people, and see the risk of at least one Covid-positive person skyrocket as the rally grows. In some places where the virus is spreading uncontrollably, such as parts of Dakota, that chance is pretty darn close to 100%, even if the gathering has only 10 people. Get 10+ people, and the map spits out chances to call it virtual certainty in many places that you’ll share space with a sick person.

Public health experts would really prefer we didn’t get together for the holidays, but they say if you make go ahead, the shindig should be outside, with as few people as possible, and everyone keeping their distance and wearing masks. But if you look at this map now, it shows that across the United States, there isn’t a perfectly safe way to come together during the pandemic. Even with all of these precautions, the risk is currently huge, especially if you are in the Midwest or are hosting someone from the Midwest. For example, in Cook County (which includes Chicago), the chance that a Covid-positive person will attend a gathering of only 10 people is around 50%. In Jones County, Iowa, that chance is staggering 99%. North Dakota, South Dakota, and Kansas also have 99% counties.

“We highlight the fact that this type of risk at the regional level has evolved,” says Joshua Weitz, quantitative biologist at the Georgia Institute of Technology, co-author of a new paper in Human behavior of nature describing the cartographic system. “At the end of the summer, it was in the south, the southeast. And the end of spring and the beginning of summer, the northeast. So there have certainly been regional changes. And at the moment, the strongest and most worrying rates of spread are in the Midwestern plains and in the high mountain region. “

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Weitz and his colleagues built the map by pulling regularly updated Covid-19 case reports The New York Times for each county. But that doesn’t tell the whole story, because many more people are infected with the virus, but they don’t know because they are asymptomatic and never get tested. So if you look at the map again, you will see an option on the left for “verification bias”. Based on serological studies – that is, people who have tested positive for antibodies that indicate their immune system has mounted a defense against Covid-19, even though they have never felt sick – researchers assume that there are in fact 10 times more cases in the United States than are reported. In areas where testing is more widely available, this rate may be lower, hence the possibility of choosing a verification bias of 5 on the map.