Fungal pathogens: a new reason to worry
The Centers for Disease Control and Prevention have just published an epidemiological study describing the increasing incidence of coccidioidomycosis (Valley Fever) over a 13 year period in the United States. Most fungal infections of humans are non-contagious, and can be acquired by the accidental inhalation of spores. Infection due to Coccidioides immitis follows this standard route of transmission, and the CDC has charted an almost 10-fold increase in human infections during the period from 1998 to 2011. It is one of the few infections due to a fungal pathogen that is considered a Nationally Notifiable Disease to the CDC.
Coccidioidomycosis in most patients causes mild disease, with self-limiting influenza-like upper respiratory symptoms. Up to 75% of patients do become sick enough to miss work or school, and approximately 40% of diagnosed cases require hospitalization. Most cases resolve well with standard antibiotic therapy directed against fungi, and typically less than 1% of cases result in bloodstream disseminated disease. Disseminated disease is extremely serious, and can have a very poor prognosis. Since the route of infection is via inhalation of spores, coccidioidomycosis is not contagious from person to person; infections occur because of environmental exposure. Universal precautions with patient care are therefore not going to be as serious as for an easily transmissible disease.
Coccidioides immitis is considered an endemic pathogen in the southwest United States, and for cases that occur in Pennsylvania, patients invariably report travel to this region in their recent history. CDC editorial comments suggest that actual rate of infection might be significantly underreported, as many cases might be asymptomatic, and some health jurisdictions do not need to report this disease. The CDC notes that this alert is consequently limited to some extent, due to the problems in consistent reporting across public health districts. Consequently, significant further study is critical to determine how much of the observed increase in Coccidioides infections are artifactual, and to what extent the number of cases are actually increasing. If coccidioidomycosis rates are truly increasing as the epidemiological data suggests, the increase is most likely due to a number of factors: altered rainfall patterns and temperatures in endemic areas might lead to easier dispersal of soil-dwelling spores, as well as increases in the disruption of soil by human activity and construction can also lead to easier spore dispersal. The CDC recommends that better awareness of the risks of coccidioidomycosis in endemic regions on the part of the public and by health-care workers can be important in prompt treatment and management of disease.