Fever, cough, sore throat, aches and pains — although the symptoms of the coronavirus are similar to those of the seasonal flu, the diagnosis is very different.

As scientists race to discover a vaccine for the contagious illness — which has so far infected more than 200,000 people worldwide since it emerged in December — early data has confirmed it is deadlier, more contagious and harder to isolate than the traditional flu.

These are the reasons why the coronavirus, officially known as COVID-19, is considered more worrisome by health officials.

Lethality

The mortality rate of the coronavirus is three times worse than the flu.

While the seasonal flu has a death rate of less than 1 percent, public health officials believe COVID-19 has a death rate of around 3 percent — and while that percentage may still seem low, it makes a stark difference in the number of lives lost when battling a rapidly spreading pathogen.

“If it’s three times more lethal than seasonal influenza — seasonal influenza kills half a million people every year. So that means there would be 1.5 million deaths [from COVID-19] if we don’t have a vaccine in a year,” said Adolfo Garcia-Sastre, a professor of medicine and microbiology at Mount Sinai Medical Center.

However, limited testing capacity around the world currently — because the virus is so new — means that many cases are going undocumented, which could affect the mortality rate.

“There are a lot of milder cases that we don’t know about and, obviously, when we document them, we will increase the number of cases and decrease the rate of mortality — but we don’t know by how much,” Garcia-Sastre said.

Containment

Both COVID-19 and the flu are transmitted similarly — typically via droplets in the air from a person coughing, sneezing or talking. But the minimum two-week incubation period for the coronavirus is much longer than that of the flu, which makes containing the spread of the virus a lot more challenging.

People infected with the coronavirus can transmit it to others even if they experience just a mild cough and feel otherwise healthy, according to the World Health Organization (WHO).

“This means that then it’s very difficult to contain because we cannot distinguish infected individuals by symptoms,” Garcia-Sastre said.

Vulnerability

The newness of the coronavirus makes it much more contagious than seasonal influenza.

While people have developed a certain level of immunity to the flu from exposure, COVID-19 was not known to science until the outbreak emerged in December 2019 in Wuhan, China.

“While many people globally have built up immunity to seasonal flu strains, COVID-19 is a new virus to which no one has immunity,” WHO Director-General Tedros Adhanom Ghebreyesus said during a briefing earlier this month.

“That means more people are susceptible to infection, and some will suffer severe disease.”

And because the symptoms of COVID-19 and the flu are so similar, the two illnesses remain incredibly difficult to distinguish without testing.

As a result, hospitals have been inundated with flu-stricken patients who fear they have COVID-19 — adding to the pressure the pandemic is already putting on global healthcare systems.

It is hard to determine what the longer-term implications of the coronavirus could be, but Garcia-Sastre believes the disease could pose a serious health crisis for at most a year before vaccines and better testing are developed, and natural immunity is built.

“By that time the virus propagation will be very low and will not cause as many problems as it does now,” he said.

In the meantime, it is important to follow expert advice on how to protect yourself and when to go see a doctor.