Providers are reporting that some Covid-19 patients who appear stable during their first week of symptoms suddenly fall critically ill between days five through 12—but doctors note there are some things patients and providers can monitor to help stave off the so-called "second-week crash."

Covid-19 guidance from clinicians at the forefront

Doctors report a 'second-week crash' among some Covid-19 patients

People who fall ill with Covid-19, the disease caused by the new coronavirus, can develop various symptoms that can range from mild to serious. But doctors around the country are reporting that some patients who develop severe cases of Covid-19 take a turn for the worse around the same time in the disease's progression.

Ilan Schwartz, an assistant professor of infectious disease at the University of Alberta, explained that most patients with Covid-19 recover in about one week, but some patients who don't recover from Covid-19 within seven days around that point enter "a very nasty second wave" of the disease. The second wave tends to begin around five to 10 days after patients first start experiencing symptoms of Covid-19. "After the initial symptoms, things plateau and maybe even improve a little bit, and then there is a secondary worsening," Schwartz explained.

The second wave of the disease often includes severe respiratory symptoms, including shortness of breath and pneumonia. Some physicians have reported seeing an increase in Covid-19 patients arriving at the hospital with pneumonia, seemingly after their oxygen levels dropped to dangerous levels during the second week of the disease.

Doctors have said days five through 10 of Covid-19 have proven to be particularly troublesome for patients with underlying medial conditions such as obesity, diabetes, or high blood pressure. In comparison, some otherwise healthy, younger Covid-19 patients may start experiencing more serious symptoms of the disease around days 10 through 12, the New York Times reports.

What causes Covid-19's second wave?

Ebbing Lautenbach, chief of the division of infectious diseases at the University of Pennsylvania's Perelman School of Medicine, said doctors are "still not entirely sure" why so many Covid-19 patients are experiencing the second-week crash.

Anna Marie Chang, an associate professor of emergency medicine and director of clinical research at Thomas Jefferson University, told the Times that she was sick with Covid-19 for nine days before her oxygen levels dropped to 88%, which is much lower than the normal oxygen saturation range of 96% to 99%. Chang said it's possible the first week of symptoms stem from the "viral illness," when "your body is developing your immune inflammatory response and trying to fight off infection." Eventually, "that system can get over stimulated, and that seems to be what causes the acute worsening … around days seven to 10," she said.

Another theory is that Covid-19 patients are crashing due to other health events like heart attacks and strokes, which providers increasingly are reporting among Covid-19 patients—even among younger patients. Research published last month in the Lancet suggests the new coronavirus may attack the lining of blood vessels throughout the body, the Washington Post reports. According to Frank Ruschitzka, a researcher from University Hospital Zurich, and colleagues who coauthored the research, that might explain why patients with severe cases with Covid-19 can experience damage to various organs, including the intestines, kidneys, and lungs.

But Merceditas Villanueva, an associate professor of medicine at the Yale School of Medicine, noted that patients who appear to crash in the second week could have "actually been sick a while," and "[t]hey've underestimated how sick they are, or they've just waited" to seek treatment.

How to prevent Covid-19's second wave

Doctors said the increasing reports of patients crashing during the second week of Covid-19 reinforces the importance of tracking patients' symptoms as the disease progresses.

"With any other disease, most people, after a week of symptoms, they're like 'OK, things will get better,'" said Leora Horwitz, an associate professor of population health and medicine at NYU Langone Health. "With Covid, I tell people that around a week is when I want you to really pay attention to how you're feeling. Don't get complacent and feel like it's all over," Horwitz said.

Some providers are teaching Covid-19 patients how to detect low oxygen levels at home, such as looking out for symptoms like fast breathing and blue lips. Some doctors even are sending patients home with pulse oximeters to measure their blood oxygen levels, the Times reports.

But others worry that encouraging patients to wait until they experience serious symptoms like shortness of breath before seeking medical attention may cause patients to wait too long before receiving treatment.

"From a public health perspective, we've been wrong to tell people to come back only if they have severe shortness of breath," ED doctor Richard Levitan said. "Toughing it out is not a great strategy," Levitan said, adding, "We should instruct patients to have a lower threshold for contacting their doctor" (Parker-Pope, New York Times, 4/30; Bernstein/Cha, Washington Post, 4/29).