Any mail that has obviously been forwarded as a chain letter warning of just about anything, even if the warning is true is almost guaranteed to be some specie of SPAM.  Sometimes messages like this refer to partially true threats, but the goal of the originator of the message is to get many people to forward the message which creates at best a an annoying kind of virus effect.  Sometimes messages like this contain attachments of links that are harmful payloads themselves.

Basically any time an email says PLEASE FORWARD THIS, it is very likely to be misleading, false or worse.

The only way for an average user to know of a new severe particular threat is to read it in the mainstream media or from your technology team. 

In conclusion the message should be ignored, but the general rule that you should never open attachments that you are not very sure about holds true.  Very sure means you know the sender and ALSO recognize BOTH the email message and the attachment as a legitimate communication from the sender.

If any of the sender, the message or the attachment don’t make sense the instructions below apply.  But because of the state of SPAM these days, mass forwarding of email is almost never an effective way of communicating this information or any information unfortunately.