The flu has a shorter time from infection to appearance of symptoms (usually about 3 days from when you are infected to when you start showing symptoms). With COVID-19, this time is estimated to be about 5 to 6 days before symptoms appear.

It also appears that for every person infected with the COVID-19 virus, that person may infect two more people, which is higher than for influenza. While it is difficult to compare the two viruses, because of differences in environment, COVID-19 will on average spread faster than influenza.

While the of symptoms for the two viruses is similar, the percentage of people with severe symptoms seems to be higher for those infected with the COVID-19 virus. For COVID-19, around 80 percent of infections are mild or show no symptoms, 15 percent are severe infections, requiring oxygen, and 5 percent are critical infections, requiring a ventilator.

Those most at risk for severe cases of the flu are children, pregnant women, elderly, those with underlying chronic medical conditions and those who are immunosuppressed. For COVID-19, the current understanding is that older age and underlying conditions increase the risk for severe infection.

More people die of COVID-19 than influenza, especially seasonal influenza. While the true death rate of COVID-19 will take some time to fully understand, the data so far indicates that the  number of reported deaths compared to reported cases is between 3 to 4 percent. The infection death rate, which is the number of reported deaths divided by the number of infections, will be lower as more testing is available. For seasonal influenza, below 0.1% of cases die. However, it’s important to note that the death rate is largely impacted by access to and quality of health care.

Source:
World Health Organization: Q&A on Influenza and COVID-19