VIRUSES ARE tiny parasites. They have a singular mission: to invade a host cell and use its machinery to replicate themselves — complete with their own genetic material — and then go on to infect other host cells. The new coronavirus, which has a comparatively large genome, is racing through part of China and beginning to spread around the world, transmitted from person to person. The family of coronavirus is so named because of a crownlike appearance of spikes — some say it looks like the sun during an eclipse, with a halo. But there is nothing sunny about its emergence as a respiratory disease that can harm and kill human beings.

This is important to understand in order to consider the proper response. For healthy people, the body’s immune system is a critical first line of defense. There are others, such as isolating the infected, hand-washing, masks, protective gear and quarantine. And once infection has set in, it is important to treat patients and help them recover.

Physical isolation, rapid diagnostics of suspected cases and monitoring of others can be vital tools. These depend on early detection and information sharing, a lesson reinforced over and over again in previous outbreaks. China’s draconian lockdown of Wuhan and other cities was an attempt to physically contain the outbreak, a worthy goal that may have been compromised by the secrecy and paranoia of China’s own leaders, who did not share information with the population. If the new coronavirus remains largely in China, then the cordon may have helped. But there is a serious possibility the virus will spread. The tiny particles are opportunists. They know no roads, no rivers nor fences; they recognize no national flags. The new coronavirus may become a global pathogen, as is influenza today.

That’s why physical measures such as limits on travel and trade, which the United States and others are now imposing on China, can become problematic. All the lessons of the 2014 Ebola epidemic were that such restrictions further harmed an already suffering region. The World Health Organization’s 2005 International Health Regulations, which cover 194 countries including the United States, call for rapid response to the outbreak at the source as the most effective way to fight an outbreak, and to “minimize unnecessary restrictions to travel and trade.”

Perhaps it is human nature to want to slam the door, but those who have been through this before wisely counsel that shutting down air routes and disrupting trade for a prolonged period will hurt more than it will help. Supply chains that are critical to the global economy, involving autos, technology and even the surgical face masks so ubiquitous in recent weeks, emanate from China and are vital to everyone else. We must move on from fear to the immense practical needs of coping with the new coronavirus if it becomes a global pandemic. Surveillance, diagnostics and improving capacity in health-care systems, as well as new therapies, are practical priorities.

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