An Australian veterinary surgery was placed under lockdown on Saturday following two fresh outbreaks of the Hendra virus that can be fatal if contracted by humans. Two horses were put down after showing signs of the bat-borne virus in separate cases in Brisbane and in Hervey Bay, 300 kilometres (186 miles) north of the city, which is home to two million people. Hendra is carried by fruit bats (flying foxes) and spread to horses through half-chewed fruit or water and food contaminated by their urine and droppings. Tests were yet to confirm the Brisbane case but chief Queensland vet Rick Symons said it was \"likely that it does have the Hendra virus.\" Ten horses have now died in a month-long epidemic -- the biggest since Hendra was discovered in 1994 -- which has swept from the country\'s far north to within 500 kilometres of Sydney. No humans have yet been infected but at least 59 people have been exposed to the virus. Four of the seven people to ever contract Hendra have died. Symons said the scale of the outbreak was unusual, with a five-fold increase in the number of samples sent for testing from suspected cases. \"It could be because of a heightened awareness of Hendra virus,\" said Symons. \"There is clearly a heightened awareness among vets and horse owners about the possibility of Hendra virus infection when a horse becomes sick.\" The vets\' surgery in Hervey Bay was sealed off after tests confirmed it was Hendra. The other case, in the Brisbane suburb of Boondall, is 10 kilomtres from the city\'s thoroughbred racing precinct and follows a scare at Sydney\'s Randwick Racecourse earlier this week. Parts of Randwick have been sealed off to keep horses clear from trees frequented by fruit bats and more than 100 racetracks across the country are being inspected for infection risks. Racing Queensland spokesman Jamie Orchard said officials were on alert and urging trainers to take precautions such as covering feed and water and keeping horses indoors at dawn and dusk -- peak feeding times for the bats. But Orchard stressed that racehorses were at relatively low risk of contracting Hendra because they were kept and fed indoors. \"The risk of a racehorse that is currently training or going to the races contracting Henda is very slim,\" he told AFP.