Doctors have been preparing for 15 years for “the big one,” a pandemic that will rock the global public health system like an earthquake. Now, with the rapid spread of coronavirus, it may be happening.

This viral outbreak probably won’t look like anything that most of us have seen. Some schools may be closed; sports schedules will be modified; travel plans will be shelved; and some workers will be advised to stay at home and telecommute. The infrastructure for delivering food and other essentials will be stretched.

U.S. public health officials on Tuesday warned of the “inevitable” spread of the virus in the United States. “It’s not a question of if this will happen but when this will happen and how many people in this country will have severe illnesses,” said Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases. Statements like that sent the financial markets into a swoon for a second-straight day.

Doctors are caught between the obligation to alert the public and the desire to avoid a panic. The World Health Organization warns of an “infodemic” in which bad information and rumors amplify the danger. Misinformation can spread faster than the disease.

Back in 2006, the United States issued its first “National Strategy for Pandemic Influenza Implementation Plan,” updated regularly since. That first version contained this stark admonition: “Uncertainty during a pandemic will drive many of the outcomes we fear, including panic among the public, unpredictable, and unilateral actions by governments, instability in markets, and potentially devastating impacts on the economy. The need for timely, accurate, credible, and consistent information that is tailored to specific audiences cannot be overstated.”

Google, Facebook and Twitter, the private guardians of the information space, have been working to keep it sanitary. Twitter has been trying to ensure that #coronaovirus delivers “credible, authoritative information.” Facebook is removing inaccurate information about the disease. Google is making verified, fact-checked information prominent in search results.

The WHO, meanwhile, is publishing simple “myth busters.” Examples: Do garlic or sesame oil prevent infection? No. Is it safe to receive mail from China? Yes.

Health authorities so far have mostly been taking the right steps. The virus was quickly sequenced genetically, vaccines are already being developed and epidemiologists are closely monitoring the spread. Doctors in Wuhan, China, where the virus began, have carefully mapped the early cases and mortality rates. The number of new cases in China has dropped sharply, which is encouraging.

Doctors caution that people should focus on the basics of good health: Washing your hands regularly is a better preventive measure than wearing a face mask; getting a flu shot is essential; if someone gets sick, they need supportive care while their own immune system fights the virus.

Health officials have tried to check the epidemic with screenings, lockdowns and quarantines. But these have had limited effect. Some travelers who arrived in Germany from Wuhan and tested negative for the virus were later found to be infected. Some clusters, in Iran and Italy, have mysterious origins. As much as doctors are learning about the novel disease, there’s much that still puzzles them.

The politics of this crisis matter. China was initially slow to react because officials there wanted to suppress bad news; Iranian authorities, similarly, may have undercounted cases initially in a cluster there. President Trump’s pronouncement two weeks ago that the virus was likely to “go away” in April missed the mark.

The intersection of a public-health crisis and a U.S. presidential election campaign is also worrisome. The U.S. and global economy will inevitably contract; as that happens, Trump will look for people to blame; he may also be tempted to take steps that would make the economic and health cost of the crisis even worse.

This is a moment when expert advice is essential to calm fears and develop effective treatments. But the viral outbreak comes at a time when the body politic is weakened in America and abroad by populist politicians and rumormongers. Analysts have warned about “The Death of Expertise,” as a recent book by Thomas M. Nichols put it. There has been a backlash against vaccinations and other public health measures around the world.

Here’s a simple, five-word statement I’d like to hear from Trump: Folks, listen to your doctor.

We sometimes say that a global crisis — a catastrophic natural disaster, say — could unite the planet and encourage everyone to pull together. With coronavirus, we’ll have a test of that proposition. This outbreak is manageable with good medicine, good information and global cooperation. But it’s going to be a bumpy ride for a while.

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