[yk]

I guess because somewhat bad diseases make good news. When you discover a new disease, then the mortality will be quite high, because you only see the cases so bad that people went to specialized hospitals, while you don't know anything about all the people with light cases, they just take a day off from work and never bother a doctor.

Once you are past the "new and incredible deadly disease" headlines, the disease is news, because it was previously reported in the newspaper.

Contrast that with a well known disease like the flu, the initial headline is not there because a flu wave is not news, if it is not a once in a decade bad flu season. (And note, once in a decade bad is only known at the tail end of the flu season, not at the start.)