Top officials at the World Health Organization this week have sought to differentiate the spreading novel coronavirus from influenza, with the underlying message that while seasonal flu cannot be stopped, countries still have the chance to limit cases of Covid-19, the disease caused by the new virus.

“This virus is not SARS, it’s not MERS, and it’s not influenza,” WHO Director-General Tedros Adhanom Ghebreyesus said at a briefing Tuesday, referencing other coronaviruses that have caused smaller outbreaks. “It is a unique virus with unique characteristics.”

By making a distinction between the viruses, Tedros has sought to rally global action against the new microbe. He and other WHO officials urged governments confronting the coronavirus to implement the public health measures that have been shown to reduce viral spread, such as isolating infected people, following those who come in contact with cases to see whether they develop illness, and suspending activities that bring together lots of people.

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“We don’t even talk about containment for seasonal flu — it’s just not possible,” Tedros said. “But it is possible for Covid-19. We don’t do contact-tracing for seasonal flu — but countries should do it for Covid-19, because it will prevent infections and save lives. Containment is possible.”

WHO officials said that such steps have enabled China, where the outbreak began and most cases have been reported, to bring down the number of new cases the country is seeing.

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“We believe this decline is real,” said Maria Van Kerkhove, a WHO coronavirus expert. And with such interventions, she said, “we believe that this is possible in other countries,” including in Iran, Italy, and South Korea, where cases have been increasing most dramatically.

Tuesday’s briefing with reporters marked the second day in a row WHO officials pressed the flu comparison as a way to call for action, which they said is all the more important because there are no approved vaccines or therapies for the coronavirus, as there are for flu.

On Monday, Tedros said, “We have never seen before a respiratory pathogen that’s capable of community transmission but at the same time which can also be contained with the right measures. If this was an influenza epidemic, we would have expected to see widespread community transmission across the globe by now and efforts to slow it down or contain it would not be feasible.”

People should try to protect themselves individually from flu strains, said Mike Ryan, the head of the WHO’s emergencies program, but at a societal and global level, “we don’t necessarily attempt to contain or stop them because we fundamentally believe they will spread unabated.”

At the briefing Tuesday, Tedros outlined the similarities that do exist between the coronavirus and influenza: Both cause respiratory symptoms and are primarily spread through small droplets from the nose or mouth. The burst of cases of the coronavirus — more than 90,000 around the world as of Tuesday morning, Tedros said, with more than 3,100 deaths — has also earned it comparisons to flu, given that the case numbers of MERS and SARS remained much lower.

But Tedros listed a number of differences as well. For one, people who have been infected with influenza but are not yet showing symptoms drive a lot of the spread of that virus. WHO officials have said that, based on data from China’s outbreak, only a tiny fraction of infected people do not show symptoms and that they do not seem to be accounting for much transmission. (Some experts have questioned the finding of limited spread from either asymptomatic or pre-symptomatic infections. Studies that could capture the full extent of such mild cases, which rely on tests that detect antibodies to the virus, are just beginning. )

Another difference: Covid-19 generally seems to lead to more severe disease than seasonal flu strains, in part because people have no immune protection against the new virus, Tedros said. Flu infections generally kill “far fewer than 1% of those infected,” Tedros said, but as of now, about 3.4% of Covid-19 cases have been fatal. (The fatality rate for Covid-19 is considered preliminary, especially given that experts are not sure how many mild cases are going undetected by health systems.)

The coronavirus, Tedros said, “causes more severe illness than flu, there are not yet any vaccines or therapeutics, and it can be contained — which is why we must do everything we can to contain it.”

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