Critical Reasoning (CR) | Re: More than 83 people have died from the symptoms of an unknow

I was stuck between A and E - I felt E was talking about an external area/ or fact and hence would not be considered.
Why would it not be A?
More than 83 people have died from the symptoms of an unknown virus. To prevent contamination, health officials are urging people in the vicinity to wear masks at all times while in public areas.

Which of the following, if true, casts the most doubt on the preventative action suggested by the health officials?

A. The type of symptoms experienced by the