Medical professionals are still scrambling to understand the full scope of COVID-19—the disease which is caused by the coronavirus. But in the meantime, there’s plenty to learn by comparing the virus to other communicable diseases, such as Severe Acute Respiratory Syndrome (SARS) and the seasonal flu.
Disease symptoms and incubation
On paper, the flu, SARS, and COVID-19 all have very similar, overlapping symptoms. In all three cases, patients have seen aches and pains, fevers, coughing, sore throat, respiratory issues, and fatigue. Those experiencing COVID-19 symptoms, however, are also likely to experience shortness of breath. As a result, patients hospitalized with severe to critical conditions typically need to be placed on a respirator. Another telltale sign may be individuals who experience a lack of taste or smell—even if they haven’t noticed any other symptoms.
The incubation period—or, the time between the exposure to the virus and the onset of symptoms—is where COVID-19 really differs from the flu or SARS. The incubation period with the flu is one to four days and approximately two to seven days for SARS. However, it can take up to 14 days (with a median incubation period of 5.1 days) for those infected with COVID-19 to begin to experience symptoms.
Transmission and spread
This heightened COVID-19 incubation period is responsible for the accelerated speed of transmission. Many who become infected are not aware of it for several days and can, therefore, unknowingly spread the disease to others. For comparison, during the initial SARS outbreak in China from 2002-2003, it took six months for cases to exceed 5,000—COVID-19 hit that number in just one month. Because SARS was easier to identify, it was likewise that much easier to contain.
Like the flu and SARS, COVID-19 is transmitted by respiratory droplets from the nose and mouth that emerge in coughs and sneezes, as well as contaminated surfaces. Medical professionals also now believe that COVID-19 can be spread through feces and other bodily secretions. Likewise, COVID-19 is also generally more contagious than the flu. Each individual infected with COVID-19 will pass the disease to 2.2 people, compared to just 1.3 for those with a common strain of influenza.
Severity and deadliness
Both COVID-19 and the flu can be lethal in severe cases, but the primary difference lies in the rate of severity. Medical professionals in China have determined that 20% of coronavirus patients have symptoms severe enough to require hospitalization (with the other 80% experiencing only mild to moderate symptoms), which is 10 times greater than the flu.
Preliminary CDC data for the 2018-19 flu season estimates a rate of hospitalization at just 1-2% of cases. Additionally, the average hospital stay for COVID-19 patients is 11 days—approximately twice as long as the five to six days for those who have had the flu.
Another common misconception is the death rate of the coronavirus compared to the flu. Though both diseases can be deadly, the flu is estimated to claim one in 1,000 patients, while COVID-19 is currently estimated to kill at least 10 people per 1,000 infected. “It’s about ten times more lethal than the seasonal flu,” Dr. Anthony Fauci testified, director of the National Institutes of Allergy and Infectious Disease, before Congress on March 11.
Although SARS had an overall higher death rate than COVID-19, the latter disease has already claimed more lives, as well as greater social and economic repercussions, in a much shorter amount of time.
The Centers for Disease Control advises that anyone experiencing COVID-19 symptoms—particularly those who have come into contact with a confirmed patient or who live in an area with a high concentration of cases—should contact your doctor immediately.