Why add the word "worrying" to your statement - just leave it neutral. No need to make people panic. It only leads to irrational behavior.

For context - what might have happened in WA could actually be a positive spin on the story. It would mean that the virus has been spreading for much longer than anticipated and the number of infected people might be 100x or 1000x the reported number. It's "positive" as it pushes the denominator up quite significantly, which would mean that the fatality rate is much closer to a "normal" Influenza than anything else.

If their profiling turns out to be correct - we're in a "much better situation" than we thought.