Doctors who responded to the survey talked about a "superhero" culture, in which they were not expected to show any signs of weakness. Others spoke about having to work through illness because there was no-one to cover for them.

Nearly nine out of 10 doctors go to work despite knowing they're too unwell to help to patients.

A survey of senior doctors, found they rarely took sick days, even when they knew they were infectious and could put patients at risk.

One reported being told to go home by alarmed patients, and another confessed to continuing to treat people after they themselves were admitted to the emergency department.

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* Sick doctors taking their bugs to work

The senior doctors union, the Association of Salaried Medical Specialists (ASMS), has called the culture of working through sickness "unsustainable", and a symptom of a public health system stretched too thin.

"They are holding the health system together at the expense of their own wellbeing, and they cannot do that indefinitely," ASMS executive director Ian Powell said.

Of the 1800 doctors who responded to the ASMS survey, three out of four said they had also gone to work despite having an infectious illness.

Nearly half the doctors who turned up sick had done so at least three times in the past year. No single district health board stood out, with sick doctors turning up to work across the country when they should not.

ASMS principal analyst Charlotte Chambers, who presented the finding at a conference in Wellington on Thursday, said the survey was sparked after a similar report at Wellington Hospital revealed a shockingly high number of doctors worked sick.

"We found it's a nationwide problem and it's worst than we thought."

Doctors spoken to agreed there was a problem, even a risk to patient health, but few seemed willing to change their own behaviour.

Wellington forensic psychiatrist Dr Justin Barry-Walsh said he was undoubtedly a clinician who worked through sickness, rarely taking more than a day off sick a year. Even when he was at home, he would spend at least half a day working from his sick bed.

"Last year I had the flu for three weeks and I had one day off. You just work through it."

He agreed the culture of not taking sick days was unhealthy and counter-productive in the longer run, but it was difficult to stay at home when it could mean patients missed out on treatment.

"Even taking one day off, you feel guilty."

For the most part, the survey shows doctors are turning up for the noblest of reasons, with a "duty to patients" the most common, followed by sessions already booked and trying to avoid placing a burden on colleagues.

Comments from doctors who responded to the survey talked about a "superhero" culture, in which they were not expected to show any signs of weakness. Others spoke about having to work through illness because there was no-one to cover for them.

Dr Hein Stander, a Gisborne paediatrician and ASMS president, said he ended up intensive care to have his heart "rebooted" earlier this year, forcing him to take about four days off work.

"But that didn't take away the guilt I felt at dropping my colleagues in it. My ill health was making their work harder."

SICK DOCTORS BY THE NUMBERS

* 88 per cent of senior doctors surveyed said they had gone to work sick, knowing it would affect their ability to work, in the past two years.

* 75 per cent said they went to work sick with an infectious disease.

* 47 per cent had gone to work sick at least three times in the past year.

SICK DOCTORS IN THEIR OWN WORDS

* "I had very bad pneumonia last winter but managed to do a full outpatient clinic while being seen myself in ED (emergency department). Not something to be proud of, I know, but I didn't feel like I could call in sick."

* "Unless I physically can't get out of bed, I would still turn up to work."

* "There is absolutely no cover for unexpected leave."

* "If I call in sick I am screwing both the patient and my colleagues who are left to deal with the mess. Far more harmful to miss a shift than to wear a mask and keep a reasonable distance."

* "I have worked a whole weekend feeling sub-optimal but not terrible only to discover that I actually had Whooping Cough."