How to explain falling COVID-19 mortality rates

Why do patients now have a better shot at surviving COVID-19 than they did just a few months ago?
Sign up for the Freethink Weekly newsletter!
A collection of our favorite stories straight to your inbox

Researchers in the U.K. recently reviewed two dozen studies involving more than 10,000 coronavirus patients admitted to ICUs in North America, Europe, and Asia.

From this data, they determined that COVID-19 mortality rates in ICUs at the end of March were nearly 60%. By the end of May, they had dropped to less than 42% — a decrease of about a third.

“There were no significant effects of geographical location, but reported ICU mortality fell over time,” researcher Tim Cook said in a news release.

But if severe cases of COVID-19 are no longer as likely to be fatal as they were just a few months ago, why might that be?

COVID-19 Mortality Rates

There are several possible explanations for the declining COVID-19 mortality rates.

One is that doctors are simply getting better at treating the disease.

In March, doctors weren’t sure how to treat severe COVID-19 cases. By May, however, they were starting to learn — through both published studies and word-of-mouth — that certain drugs and therapies appeared to be more effective than others.

If a COVID-19 patient’s blood oxygen level was alarmingly low, for example, doctors knew that blood thinners had successfully raised them in studies.

They also knew that if a patient was having troubling breathing, putting them on an invasive ventilator shouldn’t be the first resort — sometimes, simply rolling the patient onto their stomach or delivering oxygen through a nasal cannula could help.

A more selective use of ventilators alone could be partially responsible for declining COVID-19 mortality rates — the machines can save lives, but they can also damage organs, push the virus deeper into the lungs, and lead to life-threatening secondary infections.

“We’re generally learning to recognize who needs to be intubated and who doesn’t,”  Leora Horwitz, an associate professor of population health and medicine at NYU Langone Health, told the Washington Post. “We’re avoiding intubation where we can.”

Americans Surviving the Coronavirus

In the U.S., COVID-19 mortality rates aren’t only declining amongst ICU patients, they’re falling in general — on May 16, the nation’s case fatality rate was 6.1%, and now, it’s down to 3.9%

That apparent increase in patients’ chance of surviving the coronavirus may be related to doctors’ improved ability to treat the disease, but there are other possible explanations.

One theory is that the surge in new COVID-19 cases in the U.S. hasn’t had time to translate into a surge in deaths — that might come later. But another key factor is the declining age of COVID-19 patients: a few months ago, the average patient was about 15 years older than patients today, and younger people are less likely to succumb to the virus.

Another possibility is that testing is simply catching a larger share of cases now. In March, the U.S. averaged just 35,000 tests a day, with over 18% of tests coming back positive, compared to over 680,000 a day so far in July, with just 8.4% positive.

Despite a recent uptick in the positive rate, it appears that we are picking up a larger share of cases this time, making the fatality rate appear lower than in the first wave.

A few fringe theories include the possibility that summer heat is making the virus somewhat less potent; that masks and social distancing are decreasing the size of the viral load that is infecting people; and that the virus might be mutating in a way that makes it less deadly.

While it’s still too soon to say for sure what might be causing the falling COVID-19 mortality rates among patients in or out of the ICU, the news that something appears to be helping is encouraging.

We’d love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected].

Sign up for the Freethink Weekly newsletter!
A collection of our favorite stories straight to your inbox
Related
Potato chips or heroin? The debate on social media and mental health
Experts disagree on whether social media causes mental health issues in adolescents despite looking at the same data. Here’s why.
Scientists have invented a method to break down “forever chemicals” in our drinking water
Researchers have discovered a way to eliminate “forever chemicals,” or PFAS, which usually take hundreds or thousands of years to break down.
When an antibiotic fails: MIT scientists are using AI to target “sleeper” bacteria
Most antibiotics target metabolically active bacteria, but AI can help efficiently screen compounds that are lethal to dormant microbes.
The threat of avian flu — and what we can do to stop it
Avian flu is infecting cows on US dairy farms, and now a person has caught it — but new research could help us avoid a bird flu pandemic.
What’s next for COVID-19 drugs?
Paxlovid may have underperformed in a new trial, but other promising COVID-19 drugs are being authorized or in the works.
Up Next
T Cells
Subscribe to Freethink for more great stories