Results of Ongoing Investigations

The results of ongoing investigations will answer several key questions. Specifically, it will be important to know or estimate the total number of people infected, the proportion that are asymptomatic (have no symptoms), the proportion that are seriously ill, and the case-fatality rate.

In order for a virus to cause a serious pandemic, it must be easily transmitted from person to person so that it spreads rapidly. Also, it must be virulent (dangerous) and cause a significant proportion of affected people to become seriously ill or die.

Of note, the 1968 pandemic didn't make much of a stir because the infection was so mild that there was no overall increase in mortality.

Finally, a pandemic cannot occur unless most people have no immunity to the virus. This latter condition appears to have been fulfilled, but the two other conditions are uncertain.