A high-profile infectious disease researcher warns COVID-19 is in the early stages of attacking the world, which makes it difficult to relax stay-at-home orders without putting most Americans at risk.

Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the initial wave of outbreaks in cities such as New York City, where one in five people have been infected, represent a fraction of the illness and death yet to come. 

“This damn virus is going to keep going until it infects everybody it possibly can,” Osterholm said Monday during a meeting with the USA TODAY Editorial Board. “It surely won’t slow down until it hits 60 to 70%” of the population, the number that would create herd immunity and halt the spread of the virus.

Even if new cases begin to fade this summer, it might be an indicator that the new coronavirus is following a seasonal pattern similar to the flu.

During the 1918 flu pandemic that sicked one-third of the world’s population, New York City and Chicago were hit hard in the first wave of illness that largely bypassed other cities such as Boston, Detroit, Minneapolis and Philadelphia. The second wave of illness was much more severe nationwide.

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If COVID-19 retreats only to return in the fall, the number of cases could peak and overwhelm hospitals that must deal with cases of flu and respiratory viruses. Furthermore, Asian nations such as South Korea and Singapore, lauded for strict controls and rapid testing to avoid damage during the first wave, might be vulnerable to a second wave of infections, he said. 

“It’s the big peak that’s really going to do us in,” he said. “As much pain, suffering, death and economic disruption we’ve had, there’s been 5 to 20% of the people infected, … That’s a long ways to get to 60 to 70%.”

Still, there are key differences between COVID-19 and the flu. The average incubation period for the new virus is five days, compared with just two days for the flu, according to a Center for Infectious Disease Research and Policy report comparing the pandemics. 

The longer incubation period and a higher transmission rate suggest the COVID-19 virus spreads more easily than the flu.

There were nearly 80,000 deaths and more than 1.3 million confirmed novel coronavirus cases in the U.S. at noon Monday, according to the John Hopkins University data tracker. New York state has been hit the hardest with more than 26,000 deaths, and preliminary antibody testing suggests about 20% of New York City-area residents have been infected. 

Worldwide, more than 283,000 people have died and 4.1 million have been infected. 

Osterholm said only an effective vaccine can slow the virus before a large enough segment of the population becomes infected and develops some level of immunity. Even if a vaccine works, Osterholm said, it’s unknown whether it would be durable enough to confer long-lasting protection from SARS CoV-2, the virus that causes COVID-19. 

Most states are easing stay-at-home orders though patchwork measures that vary from one to the next. Georgia began opening in late April amid national criticism, allowing tattoo parlors, bowling alleys and hair and nail salons to reopen with restrictions. California has taken a slower, phased approach, allowing some retailers and manufacturers considered low-risk to resume operations. 

Governors worry about the economic harm social distancing measures have caused with shuttered businesses and the growing ranks of jobless Americans. Unemployment has reaching 15% nationwide, and a Trump administration economic adviser warned unemployment could soon reach 20%. 

Osterholm acknowledges that the nation “can’t lock down for 18 months” and said political and business leaders need to find a way to resume activities while adapting to a virus that won’t soon disappear. He doesn’t believe there has been enough of a frank assessment on the economic harm the virus will cause over coming months and its disruption to international supply chains. 

“We all have to confront the fact there’s not a magic bullet, short of a vaccine, that’s going to make this go away,” he said.  “We’re going to be living with it. And we’re not having that discussion at all.”