TORONTO -- Cases of the novel coronavirus continue to spread in Canada and around the world, but the virus does not affect all patients equally: your age and health history play a big role in how the virus may affect you.

WHAT IS THE DEATH RATE?

The biggest underlying question surrounding COVID-19 is its death rate. Experts note that the rising number of cases, regional outbreaks and undetected or unreported cases make it hard to determine.

“We don’t have the full measure of how deadly it is,” infectious disease specialist Dr. Neil Rau told CTVNews.ca.

Preliminary estimates suggest that the death rate associated with COVID-19 is between one and two per cent, which is higher than the average death rate associated with seasonal flu strains, at around 0.1 per cent.

Researchers at Imperial College London note that an exact death rate is hard to calculate because the number of confirmed cases reported only represents a fraction of the true levels of infection.

“Deaths tend to be reported promptly but there is less information on how many people have recovered from the virus,” Imperial College researcher Dr. Lucy Okell said in a press release.

“We are likely to be missing cases who have milder symptoms but there is limited information on how common these are.” 1.4833584

The report notes that all “case fatality ratios” should be viewed with caution due to the number of asymptomatic or mild cases that go unreported.

“When you hear about a higher death rate, people get scared,” Rau noted.

“But on the other hand when the virus is ‘let to rip’ and you don’t see huge numbers of causalities, you start asking yourself maybe this is not as deadly as we all think. Maybe there’s a whole ocean of other mild cases that we aren’t picking up.”

On March 28, Canada’s Chief Public Health Officer, Dr. Theresa Tam, said that about 7 per cent of Canadian cases require hospitalization, and about 3 per cent of people become critically ill. So far, one per cent of cases have been fatal.

WHO IS MOST AT RISK OF DYING?

“The biggest driver is age,” said Rau, noting that if you are young and otherwise healthy “you’re not likely to get sickened to the point of dying.”

Those with underlying health conditions such as obesity, heart disease and lung disease are at a heightened risk of developing complications related to the virus.

“Once the lungs are very affected by a virus like this -- and this happens with the flu as well -- the lungs are filled with water and the air exchange of oxygen into the blood is impaired,” Rau said.

Though there have been some questions surrounding an increased risk for smokers, Rau reiterated that a smoker would likely have to have a history of lung disease to be at an increased risk.

A recent study from the Chinese Center for Disease Control and Prevention showed that the virus most seriously affected older people with preexisting health issues.

The study, which analyzed more than 44,000 cases from China, showed that more than 80 per cent of Wuhan-related cases were classified as mild.

However, in the cases studied, the death rate was ten times higher in the elderly compared to the middle-aged. The death rate was lowest in patients under 30-years-old, with eight deaths out of 4,500 patients.

The study also noted that patients with cardiovascular disease were at the highest risk of death, followed by diabetes, chronic respiratory disease and hypertension.

The World Health Organization (WHO) also notes that the elderly and people with pre-existing medical conditions appear to develop more serious illness.

WHAT IS THE RISK FOR YOUNG ADULTS?

It was initially thought that many young adults only suffered mild symptoms of COVID-19. But health officials are cautioning people in their 20s, 30s and 40s to heed advice to socially distance amid reports that more are becoming seriously ill.

Dr. Bruce Aylward, an epidemiologist and a former assistant director-general for the World Health Organization (WHO), noted that in France more than half of coronavirus patients in intensive care are under the age of 60.

"This is dangerous in any age group,” Aylward told CTV News.

“We cannot predict who is going to have a bad outcome from this disease. We know the elderly are at a high risk, but what we don’t understand is why some very young, perfectly healthy [people] suddenly get very sick and die from this disease.”

On March 18, Ontario Health Minister Christine Elliott said the province is now seeing people in their 30s who are becoming very ill from COVID-19.

“(They are) having to be placed on ventilators,” Elliott said.

“This is a very, very serious health situation for all Ontarians right now.”

According to Canada’s public health agency, one in three COVID-19 cases in Canada involve people under the age of 40.

So far, the highest number of cases involve those aged 40 to 59, at 34 per cent of all cases, and nearly one-in-four cases involve people in their 60s and 70s. People over 60 make up 57 per cent of all hospitalizations and 52 per cent of ICU admittances.

Health officials have yet to break down how many young people are seriously ill in Canada, but U.S. officials have echoed the same concerns, citing preliminary data from Europe.

“There are concerning reports coming out of France and Italy about some young people getting seriously ill, and very seriously ill in the ICUs,” Dr. Deborah Birx, a member of the U.S. coronavirus task force, said during a White House briefing.

Brix added that young adults may continue to expose themselves to the virus because they aren’t concerned about being at risk.

“We think part of this may be that people heeded the early data coming out of China and coming out of South Korea of the elderly or those with pre-existing medical conditions were a particular risk," she said.

With files from Avery Haines