3 surprising traits of how COVID-19 affects patients, according to experts

The COVID-19 virus acts differently than other viral pathogens, capable of jumping from one person to the next before a patient shows symptoms.
Like the common cold, it can cause a loss of taste and smell, but unlike the cold, it does this without much nasal congestion.
Patients with COVID-19 who seem to be on the road to recovery can suddenly crash and go into respiratory distress within a few hours.
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COVID-19 is a respiratory illness first identified in humans in late 2019. Because it's so new, researchers are still learning about the virus's behavior as it rapidly spreads across the globe.

In addition to its ease of transmission, the following three aspects of the disease have caught the attention of medical experts.

Patients can spread the virus for days before they show symptoms

The incubation period for COVID-19 can run from just two days to nearly two weeks .

"The problem with this virus is that it is able to be transmitted before symptoms manifest," said Dr. David Hamer, an infectious disease specialist at Boston Medical Center and a professor of global health at Boston University's School of Medicine and School of Public Health. "Most viral pathogens aren't transmitted until symptoms are present."

Asymptomatic patients also make screening more difficult. Airport screenings for fever, for example, won't catch patients who aren't showing symptoms but are still contagious.

Medical experts also believe that there are a large number of people out there who have either had the bug and didn't know it, or have it now and are showing few or no symptoms.

Because of this, medical experts have been pushing social distancing as the most effective way to control the spread of the disease.

Patients lose their sense of smell

One odd aspect of the illness is that some patients lose their sense of smell while they're sick. While it's still unclear what percentage of patients experience this, the phenomenon may help identify asymptomatic or mildly ill patients.

Other respiratory infections, like the common cold, can also cause a loss of smell and taste, but it's a bit different for patients with COVID-19.

"Whenever you get a cold and have a stuffy nose, you can lose your sense of smell and have trouble tasting because of that," said Dr. Daniel Kuritzkes, an infectious disease specialist at Brigham & Women's Hospital in Boston. "What seems to be unique with COVID-19 is that the sense of smell is lost without much in the way of nasal congestion. We are now considering this a symptom of COVID-19 infection."

Patients who seem to be recovering can suddenly crash

Doctors say another unusual aspect of COVID-19 is how patients who appear to be doing well can deteriorate within a few hours to the point where they're in respiratory distress.

"We've had a fair number of people progress to severe disease that had a period of improvement followed by a sharp decline," said Kuritzkes. He added this could be due to an immune response kicking in that negatively impacts the lungs.

Because of this, experts recommend that people who have been diagnosed with or suspect they have COVID-19 carefully monitor their symptoms.

"Worrisome symptoms would be persistent fever, severe cough and increasing difficulty breathing, initially with such activities as walking or climbing stairs but if severe, even at rest," said Hamer. He added patients should contact their physician if they notice such changes.

Dr. Gabriela Andujar Vazquez, an infectious disease physician at Tufts Medical Center in Boston, said patients should also watch for chest pain, and advised anyone experiencing chest pain or breathing difficulty to head to the emergency room.

"People need to really monitor themselves for the first week. After the first week, you'll either get better or worse," said Adnujar Vazquez.

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