Fungi Associated With Lower Respiratory Infection
In a prospective study of 499 infants during their first year, researchers demonstrated a strong relationship between high levels of fungus in the household and an increased incidence of doctor-diagnosed lower respiratory tract illnesses, including croup, pneumonia, bronchitis, and bronchiolitis.
Writing in the second July 2003 issue of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine, Diane R. Gold, M.D., M.P.H., of Channing Laboratory, Harvard Medical School, Boston, Massachusetts, along with four associates, found that of the 492 homes surveyed 324 residences had high levels of at least one type of fungi. According to the authors, children in environments with more than the 90th percentile for one or more fungi had an 86 percent increased risk of developing a lower respiratory illness during their first year of life.
(All infants involved in the study were born of one or more parents who suffered from asthma or allergies.)
Fungi constitute a group of simple plantlike organisms, including yeast, some of which can cause disease.
Of the 499 infants studied, 107 (21 percent) had a report of one doctor-diagnosed lower respiratory illness during the first year on one questionnaire. Twenty (4 percent) had a second illness reported.
In drawing their conclusions, investigators controlled for sex, presence of water damage or visible mold/mildew, being born in the winter, breastfeeding, and being exposed to other children through siblings.
Although fungal spores are known to either contain or to produce allergens, the authors said that it was unlikely that allergy is the dominant mechanism through which fungal spores influence the risk of lower respiratory infection in infancy. Instead, they believe that the effects are likely due to other fungal spore components or to metabolites released from actively growing fungi.
To obtain the study data, a trained technician visited each child's home to determine household and socioeconomic characteristics and to conduct air and dust sampling. Indoor air and dust samples were collected from the bedroom where the child usually slept. At 2 months of age, a follow-up questionnaire was given to the child's primary caregiver. The research team asked about respiratory symptoms and illnesses, possible daycare attendance, and certain questions on home characteristics. Every 2 months repeat telephone calls were made to follow-up on these questions.
According to the authors, high levels of one fungus did not necessarily imply that a household would have high levels of another fungus.
In this study, the fungi that were significantly associated with lower respiratory infection were airborne Penicillium, dust-borne Cladosporium, dust-borne Zygomycetes, and dust-borne Alternaria.
"People are routinely exposed to more than 200 different species of fungi," said Dr. Gold. "Exposure occurs universally and is impossible to avoid completely. Often, there are no adverse effects, but, at times, exposure to fungi can directly and in-directly influence an individual's health."
Dr. Gold also pointed out that the independent effects of visible mold or mildew suggested that dampness-related factors other than common cultivable fungi are important. However, she noted that the study demonstrated the relationship between fungal exposure and lower respiratory illness is independent of parent-reported visible mold and mildew.