Unexplained illnesses and deaths occur relatively frequently in the United States, according to a new study by Yale researchers.
The investigators used a method called prospective surveillance for unexplained deaths and critical illnesses due to possibly infectious diseases in their study.
"We found that in a population of 7.7 million, about 40 people are dying or becoming sick from unexplained illnesses each year," said Andre N. Sofair, M.D., assistant professor of medicine at Yale University School of Medicine. "While this number might seem small, it is rather significant when it is put into perspective. Each year, in a well-served population, there are many young people who become critically ill or die without a diagnosis."
The study was published in the February issue of Emerging Infectious Diseases. The study subjects were between one and 49 years of age and lived in either the San Francisco Bay area of California, New Haven, Connecticut, Minnesota or Oregon. The patients had to have been previously healthy, with no chronic diseases and were hospitalized in an intensive care unit. These patients were reported to the investigators, who performed further diagnostic testing after the patients were discharged from the hospital.
During the first 31/2 years of the study, which is still underway, researchers looked at existing tissue and blood samples from 122 patients who had either died or became ill without a cause. Patients were divided into syndrome categories that represented their illness, such as a disease of lung or liver, and samples were tested accordingly. Although no new infectious agents were discovered, the cause of illness was determined in 28 percent of patients tested. The study also found that 30 percent of the study subjects had died.
"These preliminary findings are being used to direct programs to assist in bioterrorism preparedness and outbreak investigation," said Sofair. "Having more sophisticated diagnostic testing would be helpful in finding a cause of death or illness. He and his team found that by using new diagnostic techniques like polymerase chain reactions (PCR) researchers are able to look for the presence of a microbe's DNA or RNA without having to grow the microbe.
Other authors on the study include James Hadler of the Connecticut Department of Public Health; Rana A. Hajjeh, Wun-Ju Shieh, Jordan W. Tappero, Christopher W. Woods, Laura Conn, Sarah Reagan, Sherif Zaki, and Bradley A. Perkins of Centers for Disease Control and Prevention; David Relman and Simo Nikkari of Stanford University; Douglas Passaro, Jennifer Flood, R. Michael Hendry and Jill K. Hacker of the Emerging Infections Program, San Francisco; James Johnson and Jean Rainbow, the Emerging Infections Program, Minneapolis; and Stephen Ladd-Wilson and Paul R. Cieslak, of the Emerging Infections Program, Portland, Oregon.
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