Many people who get sick with new coronavirus experience mild, flu-like symptoms.
But COVID-19 is not equal to the flu.
So far, the new coronavirus appears to be more contagious, more deadly and has more potential to overwhelm the health care system.
Here’s how the two compare.
The ways in which COVID-19 and flu are similar
Viruses cause both flu and COVID-19, and their early symptoms are often very similar.
They can cause fever, cough and sore throat and in both cases the symptoms can range from mild to fatal.
Although none of us have any immunity to the new coronavirus, research shows that our immune systems respond the same way as influenza.
The immune cells that emerge in the blood before patients recover from COVID-19 are the same cells that we see in people before they recover from the flu.
Since both viruses are transmitted in the same way, via respiratory droplets, both require good hygiene and adequate respiratory labeling.
This means washing your hands frequently and thoroughly, covering your cough and sneezing with your elbow or a tissue and, if you are sick, avoid contact with others.
COVID-19 is more contagious
Epidemiologists use a couple of different measures to understand how far a virus is likely to spread.
One of these is called the “base play number”, otherwise known as R null, or R0.
R0 refers to the number of secondary infections generated by an infected individual, said Sanjaya Senanyake, an infectious disease specialist from the Australian National University.
“For COVID-19, that number goes from 2 to 2.5. This means that a person with COVID-19 continues to infect two or two and a half people,” said Dr. Senanyake.
This figure is higher than that of influenza, for which R0 varies, but it is estimated to be around 1.3.
This means that the new coronavirus is about twice as contagious as the flu.
COVID-19, however, appears to spread somewhat slower than influenza, which has a shorter incubation period (the time from infection to the onset of symptoms).
“When we talk about infectivity … the other measure is something we call a serial interval, which is the speed between infections,” said Dr. Senanyake.
While pre-symptomatic transmission (when the virus spreads before symptoms appear) is an important flu transmission factor, COVID-19 is not likely to be the case.
While there are people who can get rid of the COVID-19 virus 24-48 hours before showing symptoms, according to the World Health Organization (WHO), this doesn’t seem to be a driving factor in its spread.
COVID-19 is more deadly
Most people who get the new coronavirus or flu will improve.
“Eighty percent of people with COVID-19 have only mild to moderate disease that lasts around two weeks,” said Dr. Senanyake.
However, the fraction of people who develop severe disease with COVID-19 is higher than it is for the flu.
According to the WHO, 15% of COVID-19 cases are serious infections that require oxygen and 5% are critical infections that require ventilation.
The mortality rate for COVID-19 also appears to be higher than that of influenza, particularly seasonal influenza.
“For seasonal flu it tends to be around 0.1 percent,” said Dr. Senanyake.
This equates to about one in 1,000 people.
At a rate of 1%, COVID-19 would be about 10 times more deadly than seasonal flu, which is estimated to kill between 290,000 and 650,000 people worldwide every year.
But the real mortality rate will take some time to fully understand, as there are many mild cases that have probably not been reported yet.
Those most at risk
The people in the community most at risk of serious flu are:
- pregnant women,
- Senior citizens,
- people with chronic conditions (such as asthma),
- people who have compromised the immune system.
For COVID-19, those most at risk are:
- people who have recently been to a high-risk country or region (Mainland China, Iran, Italy or Korea),
- people who have been in close contact with someone who has a confirmed case of COVID-19,
- Senior citizens,
- people with chronic medical conditions,
- people who have compromised the immune system,
- Aboriginal peoples and of the islands of the Torres Strait (as they present higher rates of chronic diseases).
But health experts have warned younger adults not to be pleased with their risk, as it is not impossible for them to have a serious form of the disease or even die from it.
While children are the key drivers of influenza transmission in the community, initial data from the COVID-19 pandemic suggest that children are much less affected than adults.
No treatment for COVID-19
Unlike the flu, for which we have antiviral medicines and vaccines, there are currently no vaccines or drugs authorized for COVID-19, although there are several in development.
While the flu shot is not effective against coronavirus, it is highly recommended that you be vaccinated whenever possible.
“What we don’t want is for people to get flu and COVID-19 at the same time,” said Dr. Senanyake.