State health officials have seen such an increase in valley fever cases in early 2006 that state epidemiologist David Engelthaler is calling this “the year of the spore.”

Arizona has already had more than 1,000 cases of the spore-caused infection in just January and February this year, when usually the state averages only about 2,700 cases per year. In February, the most recent month for which data is available, total cases — 640 — were more than triple the five-year February average.

“We’re kind of looking at this now as ‘the year’ for valley fever,” Engelthaler said. “Over the past couple of months, it has really been the most dramatic increase that we’ve ever documented.”

Both 2004 and 2005 had above-average numbers of cases of the infection, which could indicate a multiseason outbreak, Engelthaler said.

Reported cases are a fraction of the actual number of infections, he added, because many people never see a doctor for valley fever if they have few or no symptoms. Actual infections could number more than 50,000 per year.

Valley fever is caused by a fungus in desert soil. When the soil is disturbed, the fungus releases spores that can lead to infection when inhaled.

Health officials can attribute some of the cases to growth in the state, Engelthaler said. Construction stirs up spore-filled dust, while more and more people never before exposed to valley fever, found mostly in Arizona and California, are moving to the desert. Maricopa and Pima counties, with their population centers, are hot spots for the infection.

Recent weather is also to blame: “The life cycle of the spore requires rainfall followed by drought,” Engelthaler said.

A very rainy start to 2005, followed by a record dry spell that extended into this year “probably has played a major factor in this dramatic increase,” he said.

Also contributing to the increase in reported cases is that health professionals are becoming more adept at identifying valley fever.

Research activity in the state focuses on identifying infection risk factors, determining the cause of the recent increase in cases, and developing a preventive vaccine, Engelthaler said.

One of those involved in the research is Dr. John Galgiani, director of the Valley Fever Center for Excellence at the University of Arizona. He called the increase in cases “striking,” and said there’s not much people can do to avoid exposure if they’re breathing and in Arizona.

Engelthaler said research indicates people whose immune systems are suppressed and those who tend to be darker-skinned are more susceptible to infection.

People concerned about being exposed should avoid digging in the dirt for things such as gardening or archaeology, avoid construction zones and dust storms and other activities where they breathe in dust, such as riding in vehicles off-road.

Engelthaler said a vaccine is likely a long way off.

“We’re going to continue to see a lot more cases,” he said.

Is it valley fever?

Valley fever is not contagious between people or animals. About 60 percent of those infected exhibit no symptoms or only mild flulike symptoms.

Those who do become ill may have symptoms that can include: Cough, fever, fatigue, night sweats, loss of appetite, chest pain, aching muscles and joints, rash of tender red bumps.

SOURCE: Valley Fever Center for Excellence at the University of Arizona