More people are dying from valley fever than previously thought, and illnesses including diabetes, lung disease, arthritis and certain cancers may increase a person's chances of dying from the disease, according to a new study.
This past year, researchers have puzzled over the rise of valley fever cases. Diagnosed cases have grown from 1,200 in 1995 to more than 20,000 in 2011, according to the Centers for Disease Control.
Now researchers have new evidence to consider: a study to be published in the November issue of the CDC's Emerging Infectious Diseases journal.
There were 3,089 documented deaths nationwide that valley fever -- also known as coccidioidomycosis -- was an underlying or contributing cause of between 1990 and 2008, an average of about 170 deaths every year, according to the researchers' study of data pulled from death certificates. That's nearly twice the number reported by the CDC in the past, which has recorded as few as 73 in 2003 to as high as 100 in 2004.
"Coccidioidomycosis remains a major cause of death in the United States," wrote Jennifer Y. Huang, who authored the study as her master's thesis at the Keck School of Medicine at the University of Southern California along with researchers from UCLA's Fielding School of Public Health.
"Given the growing U.S. population of elderly and immunosuppressed persons, the number of coccidioidomycosis-related deaths will probably increase, resulting in higher costs to the health care system."
Dr. Benjamin Bristow, a public health physician and one of the study's authors, said the paper shows there are "definitely certain groups that are more likely to die from valley fever" and the numbers shed light on those disparities.
"We're finally beginning to get a sense of how real the problem is," Bristow said.
Valley fever experts said the hard numbers on valley fever-related deaths could finally start to draw attention to the disease.
Valley fever is often referred to as an "orphan disease" that isn't very prevalent. But Dr. John Galgiani, director of the Valley Fever Center for Excellence at the University of Arizona, said the study could put a dent into that way of thinking.
"This disease was overwhelming, and it's anything but an orphan disease" for those who died, Galgiani said.
The study cements the prevalence of valley fever and draws attention to the fact that, despite its health impact, the disease has not drawn significant federal or private research funding, said Dr. George Rutherford, professor of epidemiology and preventive medicine at the University of California, San Francisco.
"There are few infectious diseases for which we tolerate this kind of mortality," he said.
Rutherford said the data establishes a base line to compare trends in the future.
"Just from a data standpoint, having this line in the sand is a good thing," he said.
The research is limited by the fact that valley fever is often not diagnosed or misdiagnosed as another disease. Researchers noted in the study that the death certificates their data were drawn from "probably underreport causes of death and can contain errors."
"I think what we're demonstrating is really the lower end of the reality," said Bristow. "My guess is there are a lot more valley fever deaths and cases that we're not finding in the data."
Warmer states a factor
The aging of the U.S. population and the rise in chronic illnesses could drive an increase in valley fever-related deaths, the researchers found. The fungus that causes valley fever is mainly found in California and Arizona, and the researchers attribute the high concentration of deaths in those states to the fact that the valley fever fungus is common there and the states are "classic retirement magnets."