At least one lab employee has tested positive for a deadly bacteria used to make bioweapons that mysteriously escaped a Louisiana research center in November . Additionally , the number of monkey 's infected by the bioterror bacterium at the Tulane Prime Research Center has increased from eight to nine and are expected to continue rising , officials say . Three of the monkeys have already been euthanized after showing signs of Burkholderia pseudomallei , which was being studied in a secure lab in another part of the 500-acre facility . The test results showed the employee was 'just at the threshold for a verified positive result ' and has not shown any symptoms of the diseases the bacteria can bring on , such as tuberculosis , according to NOLA.com . Despite thorough investigations by bothb federal and state authorities , including the Centers for Disease Control and Prevention , the cause of the contamination is still unknown . Concerns : Monkeys at the Tulane National Primate Research Center in Louisiana were exposed to a potentially deadly bacteria last fall - but authorities still do not know how or why it happened . Reach : Worryingly , the center is close to a river ( top left ) , homes and a school . Although there are no signs that surrounding areas have been exposed to the bacteria , further tests are required . The name of the employee has not been released . Questions also remain over how far the bacteria , which is primarily found in southeast Asia and northeast Australia , has spread around the complex and surrounding areas . Animals pass it in their urine and feces - potentially contaminating the ground and water around them - and others can become infected through direct contact with the contaminated areas . The bacteria may not cause an illness until days or years after the exposure , but the illness can be fatal in humans and animals , according to USA Today . The monkeys , rhesus macaques , had access to massive outdoor primate breeding cages , where around 4,000 macaques are kept . It is not yet known if the bacteria have colonized in the cages . Worryingly , the research center is just half a mile from a school and surrounded by homes . And only yards behind the facility , there is a river that leads to a lake surrounded by wildlife refuges . The contaminated primates were all at the center 's veterinary hospital at the same time last fall , leading to speculation that they could have been exposed there . Infected : At least seven rhesus macaques ( file picture ) have shown signs of exposure and three have died . Potentially deadly : Burkholderia pseudomallei . The bacteria , Burkholderia pseudomallei , can cause a potentially serious disease in people and animals called melioidosis . Melioidosis commonly involves the lungs and has a range of symptoms including fever , headache , appetite loss , muscle and joint pain . The illness may not develop for days to years . It is often mistaken as pneumonia or tuberculosis , and if left untreated , it is fatal . Several countries have looked into using the bacteria as a bioweapon because strains can be resistant to multiple antibiotics . The overall mortality rate is 40 per cent but in Thailand , where the bacteria is endemic , it is up to 50 per cent . The bacteria , which is primarily found in southeast Asia and northeast Australia , has never been found in nature in the U.S. Last week , tests by the CDC determined two further monkeys showed signs of contracting the bacteria , bring the number of infected monkeys to seven . The CDC will now be looking at safety and health practices at the veterinary hospital , the agency said . Richard Ebright , a biosafety expert from Rutgers University in New Jersey , previously told USA Today that the release was worrying . 'The fact that they ca n't identify how this release occurred is very concerning , ' he said . 'Human error is always the first explanation you should consider for a laboratory accident . 'The easiest way to transfer something from one place where it 's supposed to be , to another where it is n't supposed to be is by a worker moving from one place to the other . ' State officials are planning to test wildlife and domestic animals around the facility to see if they have been exposed . The U.S. Department of Agriculture is also working on information to give animal owners , veterinarians and laboratories on what signs to look for to determine if animals have been exposed . Authorities have previously said they are concerned that too few samples have been taken to decide whether livestock and domestic animals are at risk . Only 39 soil samples were taken from the grounds and 13 from water - far less than the 100 recommended by previous research completed in Thailand . Those results showed that there was no evidence that the bacteria had spread into the surrounding area , suggesting there was no public health risk .
At least nine rhesus macaques at Tulane National Primate Research Center were exposed to Burkholderia pseudomallei , a deadly bacteria . They were exposed even though the bacterium was being studied in a secure lab in another part of the 500-acre U.S. research complex . One employee tested positive 'just at the threshold ' Initial tests indicate that it has not spread to surrounding areas - which include a school and homes - but further tests are required . The potentially deadly bacterium , Burkholderia pseudomallei , is not found in the Louisiana and can be contracted through contact with contaminated areas .