Concern over the killer Hendra virus mounted in Australia Wednesday after a sixth horse died in an outbreak, and 26 people underwent tests after coming into contact with sick animals.
In the latest case, a horse fell ill and died at a farm south of Brisbane on Monday, not far from where other Hendra cases have been confirmed.
Six animals are now dead since the outbreak first emerged on June 20 -- five in southern Queensland state and one in northern New South Wales.
The rare virus can spread to humans, leading to fatal respiratory illness, and has killed four of the seven people who have contracted it in Australia since it was first documented in 1994.
"The recent spate of diagnosis of Hendra virus are deeply concerning," Queensland Premier Anna Bligh told reporters.
"My heart goes out to the people who are waiting for these results."
In Queensland, 17 people who were exposed to the sick horses are waiting to learn if they have contracted the deadly virus.
Nine others in New South Wales are also awaiting test results.
Named after the Brisbane suburb in which is was first documented and thought to be unique to Australia, Hendra is believed to be carried by fruit bats (flying foxes) and spread via their urine and droppings.
The bats, which have no symptoms of disease, then pass the infection to horses, possibly via half-chewed fruit or other water or food they contaminate, and these animals then transmit it to humans.
Queensland's top public health officer Jeannette Young told Sky News that humans needed to have "very high" exposure to the horses, such as through excretions, to become infected with the virus.
"There's been only seven human cases since 1994, so it's very rare," she said, adding that you cannot contract it from patting a horse.
"Whether there will be fresh outbreaks, we simply don't know."
More than 50 horses have died, or had to be put down, in 18 outbreaks of the virus since 1994.
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