Map shows the risk of hosting a Thanksgiving dinner in your county

SAN FRANCISCO (KGO) -- The timing couldn't be much worse than this. Coronavirus cases around the country -- and in California -- are spiking, just as we head into the holiday season.

Health experts are strongly recommending people avoid gathering with friends and extended family for Thanksgiving dinner and using data to back that up.

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Dr. George Rutherford, an epidemiologist at UCSF, helped us crunch the numbers based on California's statewide positivity rate of roughly 5%.

"That means if you pick someone at random to spend Thanksgiving with, there would be a 5% chance that one person was infected," he said.

But if you have a gathering with three people, that risk increases to 9.5%. Six people from mixed households bumps the risk even higher: a 22% chance someone is infected.

If you increase the invite list to 10 people, that risk goes up to 37%. At 12 people, it's a 43% chance someone at the table has COVID-19.

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Of course, the risk varies based on the spread in your community. An interactive map created by ABC7 News' data journalism team using Georgia Tech data lets you see how risky things are where you live.

It allows you to zoom into your county and also adjust the event size.

To see the map in a larger window, click here.

For example, when you zoom into San Francisco County and choose a gathering size of 15 people, the risk that someone at that dinner table has COVID-19 is 8%. In Napa County, the risk for that size gathering is 17%. In Santa Clara County, it's 10%.

As the group size gets bigger, so does the risk.

(Editor's note: The figures cited in this report are meant to be examples of the potential risk associated with group gatherings and the exponential increase in risk as the gatherings grow. The 5% positivity rate does not necessarily indicate 5% of the general population is infected and contagious at any one time.)

Things are far worse in other states in the country that are experiencing massive outbreaks.

"Some people have said gather at Thanksgiving and regather for your funeral for New Years Day," said Dr. Andrew Pavia, a doctor in Utah. "That is a bleak way to put it, but at this point, we really have to be honest."

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