We've hit 200,000 COVID-19 deaths in 6 months. What will the next 6 months look like?

It's been six months since the World Health Organization first declared COVID-19 as a pandemic. Since then, over 30 million people worldwide have been infected, and we're rapidly approaching 1 million global deaths.

The U.S. is among the world's most-affected countries, now hitting a sobering milestone: 200,000 American lives lost to COVID-19.

"This is our worst global pandemic in more than a century. And it is incredibly distressing to see the consequences. It's heartbreaking to see the ones who have been lost, the families who are grieving, other people whose livelihood has been incredibly disrupted by the economic consequences," director of the National Institute of Health, Dr. Francis Collins, told ABC News' Bob Woodruff.

Unfortunately, experts say things could get worse before they get better.

"I do think we're going to see deaths continue to increase, we'll probably expect to see another 100,000 milestone in the coming months. But I think because we've learned so much, the hope is that we'll be able to react more quickly than we were at the beginning stages of the pandemic," said John Brownstein, Ph.D., ABC News contributor and epidemiologist at Boston Children's Hospital.

Here’s what we can expect over the next six months:

Cooler months herald both flu season and fear of worsening COVID-19 outbreaks

Experts warn that colder weather and drier air will result in an uptick of COVID-19 cases this winter.

"As the colder weather will drive people indoors, we have to anticipate that there may be an acceleration in transmission and be prepared to handle the increased number of cases that may result," Amesh Adalja, MD, FIDSA, infectious disease specialist and Senior Scholar at the Johns Hopkins University Center for Health Security, told ABC News.

When flu season coincides with the ongoing pandemic, we'll have an even bigger challenge on our hands.

"If there's ever a year that you need to get your flu vaccine, get your kids vaccinated, this is the year because you really need every single protection that you can get against COVID-19. You also don't want to get exposed to COVID-19 when you're sick from another virus," Jeanne Marrazzo, MD, MPH, FIDSA, Director of the Division Infectious Diseases at the University of Alabama at Birmingham, said during an Infectious Diseases Society of America media briefing on Sept. 10.

A vaccine could be approved by 2021, but it won't be available widely for months

Public health officials say it's possible that a vaccine could be approved by the end of the year. But, approval is just the first step. Following approval, we'll need to tackle the logistical challenges of producing enough doses and distributing them fairly to everyone.

"By the time you mobilize the distribution of the vaccinations and you get the majority or more of the population vaccinated and protected, that's likely not going to happen until the mid- or end of 2021." Dr. Anthony Fauci, the nation's top expert on infectious diseases, told MSNBC's Andrea Mitchell. And that's assuming that one of the vaccine candidates works.

"But boy, Americans, we need to figure out this is not going to be a sudden snap of the fingers in December or January and everything will go back to the way it was. We're going to have many more months after that to gradually get readjusted," said Collins.

Vaccine hesitancy and pandemic fatigue will be major hurdles

Pushback on tried-and-true interventions like mask-wearing and social distancing pose serious threats to our efforts to control the spread of COVID-19. Rising vaccine safety concerns are only piling on to the problem.

"In the best of times, there are groups of people who mistrust vaccines. So that's a problem we're going to face. And if you can't get people vaccinated, we're back to where we started," Brownstein said.

As the pandemic evolves, experts are worried we will see more people become complacent with the recommended precautions.

"We are starting to see pandemic fatigue. People are getting numb to these numbers. As the numbers keep going up, people don't see the humanity in the statistics," Brownstein said.

The humanity of this particular milestone, however, is unavoidable. The virus has killed many more Americans than those who died in World War I and the Vietnam War combined. It's almost 70 times deadlier than the 9/11 attacks. Collins warned: "It's not the right time to say we're done with this. We are not. The virus is not done with us."

"We've been saying some of the same things for six months straight, and there's still an unwillingness to accept evidence-based public health decision making," said Brownstein.

We know what we have to do moving forward

We've learned a number of important lessons in the first six months: Masks and social distancing keep you and others safe. Avoiding indoor gatherings makes a big difference. Widespread testing and contact tracing are essential for controlling transmission. The flu vaccine will protect us from an even worse situation.

"Behaviors that we know work to keep the virus down may help to make the second wave not as big as we expect," Brownstein said. "But it's a matter of what this country is willing to do to stop it because we have the tools, we know what works. We have empirical evidence of these interventions, so the question is, are we willing to keep this up for another six months?"

"We ought to all look at the evidence and then make an individual decision to live up to that, because that's our best hope. Until that vaccine is in hand, and lots of people have been able to receive it, we've got many more months yet with lives at risk. And the best way to save them is for us all to take this on our own shoulders," said Collins.

We may start approaching a new normal in late spring-early summer 2021

If a vaccine is successfully deployed and public health interventions go to plan, things will begin to reopen slowly and carefully.

"If you're talking about getting back to a degree of normality, which resembles where we were prior to COVID, it's going to be toward the middle of 2021, maybe even end of 2021," said Fauci.

But, it's unlikely that life will be exactly what it was before the pandemic.

"The biggest challenge will be learning to have this virus amongst us and being able to go about our daily lives," Adalja said. "This will require an enormous amount of risk calculation for which the general public has not really had a precedent since before the measles vaccine."

Leah Croll, M.D., is a neurology resident at NYU Langone Health and a contributor to the ABC News Medical Unit.