Warnings have been issued about hoax cancer results emails.
The North East Essex Clinical Commissioning Group (NECCG) said at least two GP practices have had patients phone in worried about a hoax email.
The email looks as if it has come from NICE, the National Institute for Health and Care Excellence, and people are advised not to open it, and not to click on any links.
NICE says the contents are likely to be distressing and has reported the hoax to the police.
It is not clear exactly how many people are affected, but based on the high number of calls to the organisation it is thought to number thousands nationally.
Sir Andrew Dillon, the chief executive of NICE, said: "A spam email purporting to come from NICE is being sent to members of the public regarding cancer test results.
"This email is likely to cause distress to recipients since it advises that 'test results' indicate they may have cancer.
"This malicious email is not from NICE and we are currently investigating its origin. We take this matter very seriously and have reported it to the police."
NICE is advising people who have received the email - the subject line of which is important blood analysis result - to delete it without opening it and not to click on any links.