"Cloud" Health-Care Workers
Certain bacteria dispersed by health-care workers can cause hospital infections. Asymptomatic health-care workers colonized rectally, vaginally, or on the skin with group A streptococci have caused outbreaks of surgical site infection by airborne dispersal. Outbreaks have been associated with skin colonization or viral upper respiratory tract infection in a phenomenon of airborne dispersal of Staphylococcus aureus called the "cloud" phenomenon. This review summarizes the data supporting the existence of cloud health-care workers.

A variety of infectious agents can be transmitted from health-care workers to patients. Certain of these agents are transmissible through the air, which means that transmission from health-care workers can occur in spite of standard infection control measures such as handwashing. Thus, airborne transmission increases the likelihood that an outbreak can occur. While it is well known that health-care workers can transmit infections such as tuberculosis, varicella, and influenza by the airborne route, it is less well appreciated that they can also transmit certain bacterial pathogens through the air.

Bacteria transmissible through the air for which no data support transmission by health-care workers include Clostridium diphtheriae, Haemophilus influenzae, Neisseria meningiditis, Streptococcus pneumoniae, and Yersinia pestis. For all these agents except S. pneumoniae, the epidemiologic data supporting airborne transmission are strong enough that the Centers for Disease Control and Prevention recommends that infected patients be placed on droplet precautions. However, for all five agents, no episodes are well documented of health-care workers transmitting such infections to other patients by the airborne route, perhaps because workers with such infections may be too sick to work. For three other bacteria, Bordetella pertussis,Streptococcus pyogenes, and Staphylococcus aureus, strong data support airborne transmission from health-care workers to patients.