At least 100 soldiers have been sickened, 14 of them so severely that they ended up on ventilators; two men died from the disease.
Col. Robert DeFraites of the Army Surgeon General's Office said Tuesday that officials have found that two of the cases – not the fatalities – resulted from common bacteria. The cause of the other cases remains unknown.
A medical team is in Iraq, searching for the cause of the outbreak. At this point, investigators know more about what isn't causing the illnesses than what is.
"There's been no positive findings of any anthrax or smallpox or any other biological weapons," said DeFraites. There's also no evidence the respiratory disease SARS was involved or Legionnaire's Disease, he said.
No clear pattern has emerged among the stricken soldiers; no common times or places or Army units have been detected and there's been no person-to-person spread.
The Army is urging soldiers in Iraq to take new precautions while officials try to find the cause of the outbreak. Soldiers are being advised to avoid dehydration, to be careful when dealing with dust and to stop smoking.
DeFraites says those types of environmental issues can cause pneumonia.