Australian soldiers in the Middle East may have been exposed to blood-borne infections such as HIV because the main defence force hospital near Dubai did not properly sterilise equipment, it was revealed Tuesday. Australian Defence Force chief Air Chief Marshal Angus Houston said the oversight was disappointing but it was highly unlikely that any Australian soldier or contractor would have become ill as a result. "I would assess the risk as very low," Houston told reporters, saying the number of surgical procedures carried out at the Al-Minhad base in the United Arab Emirates was small. "However, we are making sure that we do everything we can to ensure that nobody has been inadvertently infected." Houston said no seriously wounded troops were sent to Al-Minhad. The Sydney Morning Herald on Tuesday reported that an unknown number of troops and contractors were affected by the blunder, which occurred between February 2009 and August 2010. It quoted from a memo to soldiers which said that staff at the Al-Minhad air base health facility had identified "lapses in procedure in the operation of the surgical instrument steriliser at that facility". "As a consequence the sterilisation of surgical instruments at the facility cannot be absolutely guaranteed to have met Australian standards," it said. The alert noted that the risk of infection was low given that blood-borne diseases within the defence force were extremely rare and all soldiers were vaccinated against hepatitis B.