You’re dividing deathe by reported cases to get 7.3 %. We don’t know how many cases there really are just like we don’t know how many cases of seasonal flu there are every year. Those numbers are estimates. What worldometer is reporting is treated cases. Most cases aren’t treated. When this is unraveled it will be a typical flu that kills old people more than young.
At present, it is tempting to estimate the case fatality rate by dividing the number of known deaths by the number of confirmed cases. The resulting number, however, does not represent the true case fatality rate and might be off by orders of magnitude [...] A precise estimate of the case fatality rate is therefore impossible at present.
And also, ,
Following new CDC guidelines: "As of April 14, 2020, CDC case counts and death counts include both confirmed and probable cases and deaths. This change was made to reflect an interim COVID-19 position statement issued by the Council for State and Territorial Epidemiologists on April 5, 2020. The position statement included a case definition and made COVID-19 a nationally notifiable disease.
A confirmed case or death is defined by meeting confirmatory laboratory evidence for COVID-19. A probable case or death is defined by i) meeting clinical criteria AND epidemiologic evidence with no confirmatory laboratory testing performed for COVID-19; or ii) meeting presumptive laboratory evidence AND either clinical criteria OR epidemiologic evidence; or iii) meeting vital records criteria with no confirmatory laboratory testing performed for COVID19" [source]
This change is a further example of one of the many reasons why the label "confirmed cases" (used by some to designate total cases) is incorrect (see definitions for more details). The US CDC (and Worldometer) has always used the label "Total Cases." Canada is another example where the "total number includes publicly reported confirmed and probable cases [source]
On April 14, New York City reported 3,778 additional deaths that have occurred since March 11 and have been classified as "probable," defined as follows: “decedent [...] had no known positive laboratory test for SARS-CoV-2 (COVID-19) but the death certificate lists as a cause of death “COVID-19” or an equivalent" [source].