Infection with the novel coronavirus can lead to coronavirus disease 19 (COVID-19). This can cause mild to severe symptoms. In some people, it leads to life threatening complications.

This article looks at the mortality rates of COVID-19 and the groups with the highest risk. It also explores what the illness does to the body and how it compares with the flu and severe acute respiratory syndrome (SARS).

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date.

LOS ANGELES, CA - MARCH 29: In this handout released by the U.S. Navy, Sailors assigned to the hospital ship USNS Mercy (T-AH 19) treat the first patient from Los Angeles medical facilities March 29. Mercy deployed in support of the nation's COVID-19 response efforts, and will serve as a referral hospital for non-COVID-19 patients currently admitted to shore-based hospitals. This allows shore base hospitals to focus their efforts on COVID-19 cases. One of the Department of Defense's missions is Defense Support of Civil Authorities. DoD is supporting the Federal Emergency Management Agency, the lead federal agency, as well as state, local and public health authorities in helping protect the health and safety of the American people. (Photo by U.S. Navy via Getty Images)Share on Pinterest
Most people recover from COVID-19 without needing hospital treatment.
Image credit: U.S. Navy via Getty Images.

COVID-19 can be deadly for some people. Older adults and people with existing health conditions are more at risk of serious complications, which can be life threatening.

According to the World Health Organization (WHO), about 80% of people who develop the disease have mild to moderate symptoms and fully recover without needing treatment in a hospital.

Roughly 1 in 5 people experience serious illness.

Older people may develop more severe symptoms, as may people with ongoing health conditions, such as:

  • high blood pressure
  • cardiovascular disease
  • diabetes
  • chronic respiratory disease
  • cancer

Some severe COVID-19 symptoms include difficulty breathing and a feeling of pressure in the chest.

COVID-19 can also cause serious and sometimes fatal complications, including:

The novel coronavirus enters the body through the eyes, nose, or mouth. The virus then travels down toward the lungs and inflames the lining of the airways.

This inflammation irritates the surrounding nerves, causing a cough.

The virus can then spread to the lungs and cause infection and damage, which can reduce the oxygen supply to the bloodstream.

If oxygen levels in the bloodstream decrease, the heart has to work harder to supply organs and the rest of the body with enough oxygen to function.

Meanwhile, the immune system is working to fight off the infection, and in doing so it can cause inflammation throughout the body.

This inflammation can cause blood pressure to drop, which also causes the heart to work harder to supply oxygen to the organs.

An infection in the lungs, or pneumonia, causes the lungs to become inflamed and fill with fluid. This makes it more difficult to breathe.

Pneumonia can progress to lung failure, in which case the person may need a ventilator to help them breathe.

In people with existing damage to the heart or lungs, these complications can be life threatening.

Older adults may also have a higher risk of severe complications, due to less elasticity in lung tissue and less robust immune function.

The mortality rate of COVID-19 varies, depending on where a person is in the world, their age, and whether they have ongoing health problems.

Mortality rates of COVID-19 are usually higher among older populations.

The state of the local or national healthcare system may also affect mortality rates. If hospitals become overwhelmed with severe cases of COVID-19, they may not have the resources to cope. This can increase the number of fatalities.

It is important to note that the number of COVID-19 tests in a given area significantly influences the data concerning mortality. For example, an increase in the number of people who have tested positive for the virus, including those with very mild symptoms, will change the ratio between the number of COVID-19 cases and associated deaths.

The case-fatality ratio shows the proportion of deaths among people with confirmed COVID-19. Current reports show that in the United States, the case-fatality ratio is 5.9%.

This figure would decrease with an increase in testing, as many people with mild cases of COVID-19 are recovering.

However, among older adults and people with underlying health conditions, the mortality rate may be higher.

COVID-19 symptoms can be similar to those of the flu, and both can cause respiratory disease.

However, a person tends to develop flu symptoms more quickly than COVID-19 symptoms.

Doctors refer to the time between an infection occurring and symptoms arising as the incubation period. That of the flu is only a few days, while COVID-19 symptoms can take up to 2 weeks to appear.

For some people flu symptoms are mild, while for others they can be severe and even fatal. According to the WHO, current research into COVID-19 severity indicates that:

  • 80% of cases are mild or asymptomatic
  • 15% of cases are severe, and the people require oxygen support
  • 5% of cases are critical, and the people require mechanical ventilation

This indicates that COVID-19 is more likely to become severe or critical than the flu.

Other research indicates that the flu can spread more quickly than COVID-19. Also, COVID-19 seems to affect fewer children than the flu.

Groups at high risk of severe flu include:

  • children
  • pregnant women
  • older adults
  • people with weakened immune systems
  • people with underlying health conditions

Overall, the global mortality rate of COVID-19 is higher than that of the flu. The percentage of reported deaths among people with reported cases is 3–4%.

For comparison, the mortality rate of the seasonal flu is usually under 0.1%, although this can vary depending on access to healthcare.

However, because of the high numbers of asymptomatic and mild cases, many COVID-19 cases are not reported, meaning that the mortality rate is actually likely to be much lower.

Learn more about the differences between COVID-19 and the flu here.

SARS is a disease caused by another type of coronavirus. Between 2002 and 2004, an outbreak of SARS in China spread to other countries.

Symptoms of SARS include:

SARS can also cause serious complications, such as pneumonia and severe breathing problems. According to the National Foundation for Infectious Diseases, SARS has a mortality rate of roughly 10%.

Although further research is necessary, COVID-19 appears to spread more quickly than SARS, though it may be less likely to cause severe illness.

There have been no reports of SARS in humans since 2004.

Many people with COVID-19 experience mild to moderate symptoms, and most recover without needing treatment in a hospital.

For some people, including older adults and people with ongoing health conditions, COVID-19 can cause serious symptoms and, sometimes, complications that become life threatening.

Taking precautions to avoid contracting the infection is one of the best ways to protect against COVID-19. Physical distancing, washing the hands frequently, and disinfecting surfaces can all help prevent the spread of the coronavirus.