Passengers onboard the coronavirus-afflicted Ruby Princess have been issued another health warning after a crew member was diagnosed with tuberculosis this week.

NSW Health said the male crew member was being treated in Sydney’s Royal Prince Alfred Hospital.

The crew member was diagnosed weeks after passengers disembarked from the cruise on March 19 — it would later become linked to more than 700 COVID-19 cases.

A letter, penned by Assistant Director of Communicable Diseases Christine Selvey, was sent out today and told passengers they were at a very low risk of infection.

“There is no reason to believe you are at increased risk of contracting tuberculosis from being on the cruise ship,” it said.

“Tuberculosis is spread from a person with active disease after close and prolonged contact with that person, rather than casual exposure.”

An expert panel of tuberculosis met yesterday after the man was diagnosed a few days ago.

“At this time, we do not think passengers need to be concerned about their risk of infection,” said NSW Director of Tuberculosis Services Greg Fox.

Professor Fox said health authorities were contacting people who had prolonged contact with the crew member and were screening them for the disease.

He said symptoms included prolonged cough, fever or weight loss over a period of weeks or months.

“It’s quite different to COVID, which is a much more acute respiratory illness,” he said.

“It’s possible the patient was contagious maybe one month before they developed symptoms … it is possible that they were infections during the time they were on the cruise.”

According to the World Health Organisation (WHO), tuberculosis killed about 1.5 million people worldwide in 2018 and is one of the top 10 causes of death.

The disease most often affects the lungs and is spread when infected people cough, sneeze or spit.

NSW Health said that the people who may be at risk of infection include some hospital staff, roommates, close friends and workmates.

The cruise has been linked to at least 22 deaths and is the subject of both a criminal investigation and a Special Commission of Inquiry.

The diagnosis comes as NSW again recorded zero new COVID-19 infections overnight, for the first time in more than two weeks.

More than 9,400 people were tested in the 24 hours up to 8:00pm last night and the total number of infections in the state remained at 3,092.

-ABC