From an ABC News article:
Of the 705 passengers who tested positive for the virus on the Diamond Princess, six died -- which is a death rate of less than 1%. All of the patients who died onboard were more than 70 years old.
“In China, about 12% of cases were in the elderly," said Faust. "On the Diamond Princess, four times that many older people had the disease. So again, if you’re trying to figure out what this means for the entire population, it might even mean that the overall fatality rate would be lower."
Right now, death rate estimates vary per country. The best estimates for South Korea put COVID-19's fatality rate at 0.6%, and a recent study released on the death the rate in China -- but outside hard-hit Wuhan -- hovered just above that, at 0.7%.
Right now, the best experts can say is that COVID-19 is probably more deadly that the seasonal flu, but much less deadly than other high profile outbreaks like Ebola, SARS, and MERS, with death rates of 50%, 10%, and 35%, respectively. The Center for Disease Control is planning to set up a national surveillance reporting system in 8 to 12 weeks, which will help to establish a more reliable mortality rate.