Major American cities are moving to reopen. Cautionary tales abound.
Many of the most populous cities in the United States moved cautiously toward reopening key businesses on Friday.
Gov. Andrew M. Cuomo of New York said he expected New York City, where more than 20,000 people have died from the virus, to meet several benchmarks that would allow retail stores to open for curbside or in-store pickup, as well as letting nonessential construction and manufacturing resume. The changes are part of an initial phase that could send as many as 400,000 people back to work.
Other major cities that have faced death and economic calamity from the pandemic, like Washington and Los Angeles, also announced plans to continue their reopenings by allowing restaurants, hair salons and barbershops to open their doors, as long as they follow new safety guidelines.
Mr. Cuomo joins many officials around the world in deciding that the benefits of reviving economies outweigh the risks of new infections. But as other countries are learning, those risks don’t vanish overnight:
In South Korea, which successfully brought an early outbreak to heel, more than 800 schools have either closed their doors to students or pushed back reopening days that were originally scheduled for this week. The government also closed museums, parks and many other public facilities in the Seoul area on Friday.
In Canada, a growing number of shop workers are back on the job after the easing of government orders that had closed most stores across the country, except in British Columbia. But the return to work is likely to be uneasy for many people, particularly those in hard-hit places like nursing homes and meatpacking plants.
In India, a nation of 1.3 billion people, a severe lockdown has been eased and may end entirely as soon as Sunday. But migrant workers are becoming infected at an alarmingly high rate, leading to fresh outbreaks in villages across the north, and hospitals in Mumbai are so overwhelmed that patients are sleeping on cardboard in the hallways.
In Iraq, all travel between provinces has been stopped for a second time, in response to the country’s mounting awareness of the spread of the virus. Baghdad was almost completely still on Friday, and stay-at-home orders were enforced by neighborhood blockades
In Israel, where schools reopened weeks ago, more than 100 new cases were reported on Friday, the level that Prime Minister Benjamin Netanyahu had warned would prompt the reinstatement of a strict lockdown.
After spending weeks accusing the World Health Organization of helping the Chinese government cover up the early days of the coronavirus epidemic in China, President Trump said on Friday that the United States would terminate its relationship with the agency.
“The world is now suffering as a result of the malfeasance of the Chinese government,” Mr. Trump said in a speech in the Rose Garden. “Countless lives have been taken, and profound economic hardship has been inflicted all around the globe.”
In his 10-minute address, Mr. Trump took no responsibility for the deaths of 100,000 Americans from the virus, instead saying that China had “instigated a global pandemic.”
There is no evidence that the W.H.O. or the government in Beijing hid the extent of the epidemic in China, and public health experts generally view Mr. Trump’s charges as a way to deflect attention from his administration’s own bungled response to the virus’s spread in the United States.
A spokeswoman for the W.H.O. in Geneva, where word of Mr. Trump’s announcement arrived around 9 p.m., said the agency would not have a response until Saturday.
Public health experts in the United States reacted with alarm.
The decision “will increase death rates around the world from Covid-19 and other diseases,” Dr. Keith Martin, the executive director of the Consortium of Universities for Global Health, said in a statement, adding that the world’s poor would be most affected.
“We helped create the W.H.O.,” said Dr. Thomas Frieden, the former director of the Centers for Disease Control and Prevention, which has worked with the organization since its creation in 1948.
“We’re part of it — it is part of the world,” Dr. Frieden said. “Turning our back on the W.H.O. makes us and the world less safe.”
If the reopening of offices, restaurants and other public places within countries amid the pandemic has seemed dizzying, the rules on travel between nations are shaping up to be bewildering.
Travel bubbles and airline corridors to allow free movement between certain cities or countries, quarantines and an assortment of other measures add up to a puzzle that even the most intrepid traveler will likely have trouble navigating.
Nowhere are the logistical challenges more daunting than in Europe, where optimistic pronouncements about easing restrictions in time for the summer travel season have run into the reality of a patchwork of policies.
For people living across the continent, the sudden closure of borders came as a shock, fundamentally reordering life for millions who came of age in an era defined by frictionless travel between the 26 countries that are part of the so-called Schengen zone.
“It would be great if all this could be compressed into something easy to understand, but it is a very complex picture,” said Adalbert Jahnz, a spokesman for home affairs, migration and citizenship at the European Commission, the executive branch of the European Union.
European officials are working on an interactive map with all the rules among member states in one place. Even when the platform is up and running, though, it will likely offer a confounding picture of closed and open borders, with individual member states reaching bilateral and multilateral agreements with neighbors.
For instance, Bulgaria, Serbia and Greece are expected to open borders to each other on June 1. Greece, desperate to save its tourism industry, also released an expanded list on Friday of 29 countries from which it will allow travel starting June 15.
The Czech Republic, Hungary and Slovakia have already started implementing a similar arrangement.
France, Germany and other West European nations have talked about easing border controls to other E.U. member states on June 15. That is the day that the European Commission’s guidance calling for the suspension of all nonessential travel into the E.U. will expire.
The issues confronting bureaucrats regarding travel from outside the bloc is perhaps even more difficult than the issues within the zone.
If one country lets in travelers from outside the bloc — and borders between countries in the E.U. are fully open — then, in effect, every country has done so.
The European Commission, which can only offer guidance, is still discussing what posture to take before the June 15 deadline. But officials said that it would be hard to do anything short of either keeping the guidance in place as it stands or completely lifting it.
If they were to call for more targeted restrictions on countries based on criteria like virus caseloads, it could create a whole new set of scientific, diplomatic and political challenges.
If there is one bright spot for believers in a united Europe, it is that the value of open borders among its countries will likely not soon be taken for granted after this pandemic is over.
For Mr. Jahnz of the European Commission, the crisis has shown “just how essential borderless travel is to our economy and our way of life.”
When experts recommend wearing masks, staying at least six feet away from others, washing your hands frequently and avoiding crowded spaces, what they’re really saying is: Try to minimize the amount of virus you encounter.
A few viral particles cannot make you sick — the immune system would vanquish the intruders before they could. But how much virus is needed for an infection to take root? What is the minimum effective dose?
A precise answer is impossible, because it’s difficult to capture the moment of infection. Scientists are studying ferrets, hamsters and mice for clues but, of course, it wouldn’t be ethical for scientists to expose people to different doses of the coronavirus, as they do with milder cold viruses.
Common respiratory viruses, like influenza and other coronaviruses, should offer some insight. But researchers have found little consistency.
For SARS, also a coronavirus, the estimated infective dose is just a few hundred particles. For MERS, it is much higher, on the order of thousands of particles.
The new coronavirus, SARS-CoV-2, is more similar to the SARS virus and, therefore, the infectious dose may be hundreds of particles, Dr. Rasmussen said.
But the virus has a history of defying predictions.
Generally, people who harbor high levels of pathogens — whether from influenza, H.I.V. or SARS — tend to have more severe symptoms and are more likely to pass on the pathogens to others.
But in the case of the new coronavirus, people who have no symptoms seem to have viral loads — that is, the amount of virus in their bodies — just as high as those who are seriously ill, according to some studies.
You can become a better reader right now.
Are you finding it difficult to sit down and read? You’re not alone. Here are a few strategies that can help you get more out of your next book.
Reporting was contributed by Ian Austen, Choe Sang-Hun, Andrew Jacobs, Apoorva Mandavilli, Donald G. McNeil Jr., Alissa J. Rubin, Marc Santora, Kai Schultz, Daniel Slotnik, Sameer Yasir and Vivian Wang.