Aaron E. Carroll and Ashish Jha: This is how we can beat the coronavirus

The disparity between the parties was underscored Thursday afternoon when Los Angeles Mayor Eric Garcetti and California Governor Gavin Newsom, both Democrats, issued rapid-fire orders closing down all non-essential businesses, first in the city and then in the entire state, a jurisdiction of 39.5 million people.

This divergence reflects not only ideological but also geographic realities. So far, the greatest clusters of the disease, and the most aggressive responses to it, have indeed been centered in a few large, Democratic-leaning metropolitan areas, including Seattle, New York, San Francisco, and Boston. At Thursday’s White House press briefing, Deborah Birx, the administration’s response coordinator, said half of the nation’s cases so far are located in just 10 counties. The outbreak’s eventual political effects may vary significantly depending on how extensively it spreads beyond these initial beachheads.

If the virus never becomes pervasive beyond big cities, that could reinforce the sense among many Republican voters and office-holders that the threat has been overstated. It could also fuel the kind of xenophobia that Trump and other GOP leaders, such as Senator Tom Cotton of Arkansas, have encouraged by labeling the disease the “Chinese virus” or the “Wuhan virus.”

“There’s a long history of conservatives demonizing the cities as sources of disease to threaten the ‘pure heartland,’” says Geoffrey Kabaservice, the director of political studies at the libertarian Niskanen Center and the author of Rule and Ruin, a history of the modern Republican Party. “That’s an old theme. So that could be how it goes down.”

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Conversely, the charge that Trump failed to move quickly enough may cut more deeply if the burden of the disease is heavily felt in the smaller communities where his support is deepest. Most medical experts believe that, eventually, the outbreak will reach all corners of the country, including the mostly Republican-leaning small towns and rural areas that are now less visibly affected.

“There’s no reason to think that smaller communities will be protected from it,” Eric Toner, a senior scholar at the Johns Hopkins Center for Health Security, told me. “It may take longer for it to get there, but as long as there are people coming and going … the virus will eventually find its way to rural communities as well.”

Still, some experts believe that, throughout the outbreak, the greatest effects will remain localized in large urban centers. “The bottom line is, every epidemic is local, and the social networks and the physical infrastructure in any specific geographic area will determine the spread of the epidemic,” Jeffrey D. Klausner, a professor of medicine and public health at the David Geffen School of Medicine at UCLA, told me. “Particularly, respiratory viruses are dependent on close social networks and are going to spread much more efficiently in crowded, densely populated urban areas.”