(NaturalNews) A newly discovered and highly lethal virus strain begins with symptoms similar to that of a cold but can quickly lead to severe respiratory crisis."This virus has the capability of causing severe respiratory illness in people of all ages, regardless of their medical condition," said John Su, of the Centers for Disease Control and Prevention.The virus was discovered by infectious-disease expert David N. Gilbert, who noticed that otherwise healthy patients were being stricken by pneumonia so severe that they would die without oxygen treatment. The dangerous symptoms developed within only one or two days of initial cough and fever symptoms.Since Gilbert's discovery of the virus in Portland, Oregon, outbreaks have been identified at military bases in Washington, Texas and South Carolina.The disease is a variety of adenovirus, the family that includes 51 infectious agents responsible for diseases such as colds, pink eye, bronchitis and the stomach flu. A mutation has apparently occurred in a virus called adenovirus 14, making it much more lethal. In the first outbreak examined by Gilbert, seven of 30 hospitalized patients died."That's an incredibly high mortality rate," Gilbert said.One of the patients who survived was 18-year-old Joseph Spencer. After experiencing severe, flu-like symptoms including chills, fever and vomiting, Spencer went to the hospital, where he was placed in intensive care and treated for 18 days."We told the family we didn't think he was going to survive," Gilbert said.Spencer was eventually discharged, but says he still feels weak and short of breath, and has had problems with his memory.Tests have determined that more 50 percent of adenovirus infections in Oregon are now caused by the new strain of adenovirus 14."That's shocking," said Paul Lewis, an Oregon health investigator. "It went from being imperceptible to being the majority."Health officials caution that while the vast majority of cold-like infections are harmless, patients whose symptoms continue getting worse should see a doctor.