Environmental Engineering Reference
In-Depth Information
A. Infections
A number of fungal species can cause infectious disease. However, compared
to bacteria and viruses, fungal infections have played a relatively minor
historical role in causing human suffering and death. In the past two decades
there has been a significant decline in skin disease, and a significant increase
in systemic disease, caused by fungal infections. This is due, in the latter
case, to significant increases in the population of individuals who are sus-
ceptible to systemic fungal infections. This susceptible population includes
individuals with immune system deficiencies who would have normally
died early in life; patients on immunosuppressive drugs; and other at-risk
patients with cancer, on long-term antibiotic therapy, or with certain infec-
tious diseases. Acquired immunodeficiency syndrome (AIDS) is the most
prevalent of such infectious diseases. The epidemic increase in AIDS infec-
tions has resulted in a corresponding increase in life-threatening fungal
infections, most notably by species of the genera
Candida
and
Cryptococcus
.
Fungi that cause systemic disease are saprobic organisms that become
infectious when disruption of a human host's physiology, microflora, or
immune system occurs. Immune-compromised individuals who have AIDS
or are being treated with immunosuppressive drugs are of special concern
because they are potentially exposed to both true pathogens and opportu-
tunistic fungi is of major concern in hospital environments where special air
filtration systems are often installed to protect patients. Most notable are
efforts to control exposure to
Aspergillus fumigatus
, which is responsible for
most aspergillosis infections. Other
Aspergillus
species of concern include
A.
flavus, A. niger,
and
A. terreus
. Outbreaks of nosocomial (hospital-acquired)
aspergillosis have been associated with new construction as well as renova-
tion activities.
Life-threatening fungal infections in immune-compromised and other
patients are often associated with
Candida
spp
. Candida
grows in a yeast-like
fashion and is a normal part of the microflora of humans. As such, filtration
Table 6.4
Pathogenic and Opportunistic Fungal Species
that Cause Systemic Infections
Pathogenic
Opportunistic
Cryptococcus neoformans
Candida
sp.
Histoplasma capsulatum
Aspergillus
sp.
Coccidiodes inmitis
Trichosporon
sp.
Blastomyces dermatidis
Fusarium
sp.
Paracoccidiodes braziliences
Pseudoallescheria boydii
Mucor
sp.
Rhizopus
sp.
Absidia
sp.
Rhizomucor
sp.