A third person has been diagnosed with monkeypox, Public Health England (PHE) said.
This follows the second ever case being diagnosed at the hospital earlier this month.
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The individual is a healthcare worker who treated a patient at Blackpool Victoria Hospital in September, before their infection was diagnosed.
Dr Nick Phin, deputy director of the national infection service at PHE, said the case was "not wholly unexpected".
Mrs Marie Thompson director of nursing, Blackpool Teaching Hospital, said: "As a trust we have been working within the guidance of Public Health England. All of the staff have been traced and put in active surveillance and we have seen that it is working and that the staff member was picked up early and is getting quick treatment.
"We know monkeypox is a very rare disease, it is new to this country. This is a virus along the lines of having chickenpox. Symptoms are flu like, you get a rash, but people recover within a few weeks."
She added the hospital had been offered the smallpox vaccine so that if staff were to develop the symptoms the vaccine would make it a milder illness.