"I really would like to see some of the hysteria settle down. I am not contagious, and none of us who have been working over there wants to put anybody at risk." Nurse Libby Bowell with a colleague in Liberia. Bowell, like other health workers returning from the Ebola front-line in west Africa, is under voluntary home isolation for 21 days (the longest possible incubation period). Twice a day she takes her temperature, and logs her movements with health officials. She avoids crowds and visiting friends or family. Publicly, messages from local health officials continue to be reassuring. Australian hospitals are well prepared, they say. Border protection officers are screening those who have travelled in west Africa at the country's airports. The chances of ebola arriving here are small, and if it did come it would be easily contained.

Yet the words and pictures from abroad seem to tell a more worrying story. The United Nations Security Council heard this week from its own head of emergency response, Anthony Banbury, that the deadly disease (with an estimated fatality rate of 70 per cent) was in a "race" with humanity, and the disease was winning. Royal Melbourne Hospital staff demonstrate personal protection equipment. Credit:Angela Wylie The World Health Organisation warned that the infection rate could reach 5000 to 10000 new cases a week by December. President Obama, who has sent troops to west Africa to help combat the outbreak, left open the door to travel restrictions to the region. In the US, where two nurses were infected by a patient they were treating in a Texan hospital, authorities are scrambling to tighten protective protocols.

Seventy-five staff at the hospital had to sign legal undertakings to avoid public transport and areas where people were congregating. In Europe there were scares in France and Denmark, and in Spain a plane was grounded and a passenger taken under guard to hospital after exhibiting signs of fever during a flight. Some experts in the US are starting to question whether the outbreak - by far the largest and fastest spreading Ebola outbreak the world has known - is proving more infectious than previous manifestations of the disease. Former US army virologist Dr Phillip Russell warned that "Scientifically, we're in the middle of the first experiment of multiple, serial passages of Ebola virus in man. God knows what this virus is going to look like. I don't." Health authorities in Australia continue to say that someone has to be in direct contact with the bodily fluids of an affected person, or touch a surface contaminated with those fluids, to contract the disease.

But not everyone endorses such a simple, black and white message. Sydney academic Raina MacIntyre, head of the School of Public Health at UNSW, has publicly broken ranks on the issue. "Some policy and guidelines around infection control are driven more by ideology and paradigms of thinking than science," she told Fairfax Media. "It goes back to this issue of transmission of infection, which is central to the debate around Ebola. The view is that infection can be categorised into airborne, droplets and contact. And that Ebola [is relegated] to contact transmission. "Yes, contact is the predominant mode of transmission, but there are studies that show Ebola can be transmitted in other ways. It is a relatively under-studied disease, so to be making very emphatic statements about how it's transmitted is not wise."

Professor MacIntyre wants Australian health workers to be equipped with respirators (which eliminate exposure to fine, airborne disease particles) should they have to treat Ebola patients. But masks, not respirators, are currently standard in hospital protocols for treating Ebola. "I'm sympathetic to the messages being conveyed by health authorities because the last thing you need in public health is confusion," says another Australian health expert, who didn't wish to be named but leans towards Professor MacIntyre's argument. "It's a fine line between wanting a consistent message, and abandoning necessary scientific scepticism. There is still uncertainty about modes of transmission, and there is some debate about what constitutes an at-risk contact." But MacIntyre's views are strongly rejected by the ANU's Professor of Infectious Diseases, Peter Collignon, who sides with mainstream advice.

"I don't see the evidence to show that [the current outbreak] is any different to what we have believed, which is that it is principally spread by bodily fluids and secretions ... and that you really have to have reasonable exposure to someone who is fairly sick and advanced in illness if you are going to get it," he says. McIntyre believes it's concerning that trained healthcare workers are catching the disease. But Libby Bowell says nearly all who have caught it have done so outside work. "It's not dissimilar to Aboriginal health workers - when you go home [in west Africa], you are still on call, and if someone is sick in the community they come and seek you out," she says. A spokeswoman for Medecins Sans Frontieres, Lauren King, says all local MSF workers who have so far contracted the disease have done so outside of work. Two international staff had, however, been infected, and "investigations were pending" into how they contracted it, she said.

NSW chief health officer Dr Kerry Chant says she will amend existing protocols if the advice from the WHO or the Centre for Disease Control in the US suggests the disease is proving more contagious than at first thought. "We are watching and monitoring the international evidence and we are prepared to rapidly change in the light of changing circumstances," Dr Chant says. "But at the moment we don't have advice which would support changing views on modes of transmission." Health authorities hope Australia's first Ebola case - if it arrives - will turn up at a hospital, not a GP's surgery, though the Royal Australian College of General Practitioners says it's confident good advice has been issued to doctors. The NSW director of communicable diseases Vicky Sheppeard, says "GP's are discouraged from doing any tests or taking any samples if they suspect Ebola.

They can take the history, we advise gloves and mask to interview the person, then we give them a 24-hour number to ring for further advice." But one doctor said it was becoming increasingly clear there was no room for the "tiniest little mistake" around an infected patient. "You have to know how to de-gown and de-glove in exactly the right way." Loading Professor Collignon says fear could be the worst enemy, deflecting timely treatment for other diseases like malaria. "We run the risk of being so paralysed with fear that people could die from something [else] that was eminently treatable because nobody would go near them or do the appropriate tests," he said.