Paris - The first home-grown European case of Ebola, in a Spanish nurse, was avoidable, virologists said Tuesday as the EU demanded answers from Madrid.
Though there is always a threat to health workers of infection with the virus spread through contact with body fluids, the risk is small and well-understood and existing protections effective, the specialists said.
"If appropriate containment measures were adopted this really should not have happened," said Jonathan Ball, a virology professor at the University of Notthingham.
"It will be crucial to find out what went wrong in this case so necessary measures can be taken to ensure it doesn't happen again."
The Spanish government said Monday that a nurse had contracted the haemorrhagic fever after treating two patients who died at a Madrid hospital -- both missionaries infected in West Africa, where Ebola has claimed more than 3 400 lives.
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The 40-year-old woman is in a stable condition.
The European Union on Tuesday demanded an explanation from Spain as to how she could have become infected.
In comments to Britain's Science Media Centre, experts said protective suits worn by health workers, coupled with safe disposal of patients' bodily waste, substantially reduced the risk.
"The recent report of a Spanish nurse who has contracted the virus... is of concern as it suggests that the barrier methods and training were not sufficient to protect healthcare workers and prevent secondary infection," said virology professor David Evans of the University of Warwick.
Waste disposal key
Ben Neuman, an expert from the University of Reading, said investigators will have to look closely at the disposal of waste at the hospital where she worked.
"Nurses face a problem in that a person who is sick with Ebola can make quite a lot of highly infectious waste, as the patient loses fluid through diarrhoea and vomiting. Those bodily fluids can contain millions of Ebola viruses, and it only takes one to transfer the infection."
Another concern was that the nurse had gone on holiday the day after the second patient died on September 25, though authorities have not said where she went.
After contracting the virus, it takes up to 21 days for a person to develop symptoms, which is when they become infectious.
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"Reality is that anyone who suspects that they have been exposed to the virus, unless they were properly protected from infection, should not travel until this 21-day incubation period has passed," said Ball.
The case underlined the importance of following protection measures to a tee, the experts said.
But there was always a risk, however small. A tiny amount of Ebola-containing liquid could splash on protective garments and be transferred to a person's skin, for example.
"As the African outbreak perfectly illustrates, healthcare workers put their life on the line, so everything should be done to ensure that risks are minimised as much as possible," said Ball.
It was also a reminder that the risk of such sporadic exports will increase as more and more people become infected in West Africa.
"That is why it is so important for the international community to ramp up their efforts to combat this deadly disease," Ball said.