(WASHINGTON) — Five years ago, the World Health Organization declared the COVID-19 outbreak to be a pandemic, leading to stay at-home orders and shutdowns across the U.S. and world.
The nation looks much different since then, and scientists and researchers have learned a lot about the virus, including how it infects people, the best forms of treatment and what puts someone at risk for long COVID.
There are still many questions, however. Health care professionals are working to find answers, such as how many people have truly died, how long the virus spread undetected in the U.S. and its origins.
“We know this emerged in China, around the city Wuhan. That’s very clear,” Dr. Cameron Wolfe, an infectious diseases specialist and a professor of medicine at Duke University School of Medicine, told ABC News. “We know when [the] medical community identified it, but we don’t know quite how long it was circulating before then. I think it’s caused some of the consternation.”
How many people have died of COVID-19?
As of March 6, at least 1,222,603 Americans have died of COVID-19, according to data from the Centers for Disease Control and Prevention.
The U.S. currently has the highest number of deaths of any country in the world, according to the WHO.
Experts, however, believe the true death toll is higher.
“More than a million people is a tragedy into itself, let’s start with that obvious fact,” Wolfe said. “I think the numbers are really hard to pin down for one key reason.”
Determining the exact cause of death can be complicated, Wolfe explained. Someone could die of COVID pneumonia — a lung infection caused by the virus — or die from a heart attack after contracting COVID.
Another example is an older adult who contracts COVID-19. They may become dehydrated, break a bone — because dehydration negatively impacts bone health — and suffer fatal complications, Wolfe said.
“How you count those outcomes is really important because, to me, that person wouldn’t have had their heart attack or that person wouldn’t have become dehydrated and fallen over and landed in the hospital if not for COVID triggering that event in the first place,” he said. “So, I actually think it’s really important to count those as COVID-associated mortalities, but they’re hard to count. They’re hard to track.”
Globally, more than 7 million people have died due to COVID-19, WHO data shows, although the agency says the pandemic caused an estimated 14.83 million excess deaths around the world in 2020 and 2021.
What is the mechanism behind long COVID
Scientists are not sure what causes long COVID but have identified certain risk factors such as an underlying health condition. Long-COVID symptoms can last for weeks, months or even years and can include — but are not limited to — fever, fatigue, coughing, chest pain, headaches, difficulty concentrating, sleep problems, stomach pain and joint or muscle pain, according to the CDC.
Research has found that patients with long COVID tend to have lower cortisol levels and lower testosterone levels.
“There are several questions that we still do not have answers for. What is the mechanism of the disease? Why do some people get more sick than others?” Dr. Fernando Carnavali, an internal medicine physician and a member of the team at Mount Sinai’s Center for Post-COVID Care, told ABC News.
Carnavali said scientists are using machine learning to study groups of long COVID patients in an attempt to determine the mechanisms that cause the condition.
“Do we have a single answer? Not as of yet, and most likely, perhaps we’ll have more than one answer,” he said.
Carnavali said the mechanism may not be the same for every long COVID patient. Additionally, people may have different symptoms due to different genetic predispositions.
“Some of the deficits that we have five years ago still remain, but I think that we should all understand and be hopeful that … researchers using machine learning will [provide] us some of the answers that we need as clinicians,” he said.
When did COVID enter the United States?
It’s still not exactly clear when the virus first entered the U.S. The first confirmed case in the country was Jan. 20, 2020, in a man in his 30s in Washington state, who developed symptoms after a trip to Wuhan.
However, studies have suggested the virus may have been circulating undetected for months beforehand.
Although the WHO was first notified on Dec. 31, 2019, about the mysterious pneumonia-like illness that originated in Wuhan, experts say it is likely that in an age of global travel, the virus was in the U.S. before then.
“It’s more likely circulated before Jan. 1 [2020]. It doesn’t seem unreasonable, November, December,” Dr. Lisa Olson-Gugerty, an associate teaching professor for Syracuse University and practicing family nurse practitioner in emergency medicine, told ABC News. “COVID masquerades itself as a flu-like illness, upper respiratory-like illness, like many other viral illnesses. It’s not easy to say, ‘Hey, I think this must be a new thing, and I’m going to tell everyone.'”
She went on, “I think it takes a bit of collective time to recognize a new viral strain, and it doesn’t seem unreasonable [there were] cases that could have been recognized as COVID before the date of release of information.”
Where did the virus come from?
There are two theories about where the virus, known as SARS-CoV-2, originated.
At least four U.S. agencies believe the virus was a result of natural transmission and that the virus jumped from animals to humans at a wet market.
The FBI, the CIA and the Department of Energy – the latter with “low confidence” — believe the COVID-19 pandemic “most likely” was the result of a laboratory leak in China.
Additionally, an April 2023 report from Senate Republicans conceded that “both hypotheses are plausible” but that the evidence points to the virus emerging from an accidental lab leak in Wuhan — and there may even have been multiple leaks.
If the virus did come from an animal, there are questions about which species may have spilled the virus over from animals to humans.
“I’ve seen a lot of conflicting information,” Olson-Gugerty said. “Did it come from a bat? Did it get into raccoon dogs or civet cats? Or was it a lab-created virus in Wuhan, China There does seem to be a jury that’s out.”
Wolfe said we may never know the true origins of SARS-CoV-2, but trying to answer the question helps scientists and public health professionals learn how to mitigate the spread so a pandemic — or even widespread illness — doesn’t happen again.
“This was the same question that happened during the Ebola pandemic, when we had to say, ‘Where did this come from? How can we educate people to minimize this future risk?'” he said. “It was important to examine where COVID-19 came from to try and put things in place that would stop that happening.”
He added, “We certainly, I would say, have better safety mechanisms now in place … so there are some good things that have come out of this.”
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