Deadly strep may warrant post-exposure prophylaxis
'This is really an impressive bug'
Health care workers exposed to patients with group A Streptococcus infection -- particularly those with the toxic shock syndrome caused by the pathogen -- may need to be administered post-exposure chemoprophylaxis, reports a leading strep epidemiologist at the Centers for Disease Control and Prevention in Atlanta.
Though sensationalized in the media as the "flesh-eating bacteria" due to its ability to cause necrotizing fasciitis, group A Streptococcus is raising legitimate concerns in the medical community due to sporadic but deadly outbreaks of both community-acquired and nosocomial infections.
As outlined at several recent meetings at the Centers for Disease Control and Prevention, surveillance has been beefed up for the pathogen, and updated guidelines are being drafted for hospitals. (See guidelines, p. 24.) While the guidelines call for infection control practitioners to begin an initial investigation at the appearance of a single case, a CDC epidemiologist recently suggested that it may be time to go further and consider offering post-exposure chemoprophylaxis to health care workers. The measure was suggested to the CDC Hospital Infection Control Practices Advisory Committee (HICPAC) at a recent meeting by Ben Schwartz, MD, medical epidemiologist in the CDC childhood and respiratory diseases branch.
"Should those [health care workers] receive prophylaxis as they do in post-contacts of patients with meningococcal disease?" he asked. "I think we are dealing with an infection that is more severe than meningococcal infection. . . . If I were a health care worker, I would certainly want prophylaxis."
Though only rudimentary surveillance is in place nationally for group A strep, reports of nosocomial clusters are being compiled by the CDC. Those have involved transmission between patients and health care workers, including an outbreak reported last year at a hospital in Ontario, Canada, that resulted in three patient deaths and pharyngitis infections in six staff. (See Hospital Infection Control, May 1995, pp. 66-67.) Another outbreak in an intensive care unit in a Denver hospital began with a patient who died of toxic shock syndrome, and resulted in two nurses developing pharyngitis and two other patients developing severe pneumonia, Schwartz said. Of primary concern is that the streptococcal toxic shock syndrome could be transmitted directly to a heath care worker from an infected patient, he said, citing the case of a emergency medical worker who acquired the syndrome within 24-hours of resuscitating an infected child.1 Clusters of infection can also be associated with a health care worker who is an asymptomatic carrier, and have generally occurred in surgical and obstetric settings.
"Group A Streptococcus is special is because of its virulence," Schwartz told HICPAC. "We have an illness with a case fatality rate that exceeds 70% and progresses rapidly within 24 to 48 hours leading to shock and organ system failure. This is really an impressive bug. Necrotizing fasciitis -- if any of you have seen it clinically -- is really an impressive condition."
While ongoing efforts are under way to add group A strep to the list of reported infections in all states, CDC projections based on limited surveillance data indicate as many as 15,000 cases may be occurring annually in the United States, reported Jay Wenger, MD, chief of the CDC childhood and respiratory diseases branch.
"The early results from some of these surveillance studies suggest that the incidence of disease is between 1.5 to 8 [cases] per 100,000," he said at a recent meeting of the CDC board of scientific counselors. "It varies pretty widely by area. When we use our best guess as to what this actually means, we think there are probably about 10,000 to 15,000 cases of invasive group A strep a year."
Overall, it appears the infection has increased both in virulence and prevalence, possibly due to increases in both particular invasive strains and susceptible populations.
"Clearly what all the newspapers were asking and what we're asking is -- 'Is it really increasing?'" Wenger said. "I think the surveillance data that we have collected suggest that it is, although not by orders of magnitude. We might have two or three times what we had we had in 1980, or something like that."
Young children and the elderly appear to be at highest risk, along with those who are immunosuppressed, intravenous drug users, and those already infected with varicella.
"A lot of the newspaper reports that came out really emphasized that this could happen to anybody, including non-immunosuppressed, normal, healthy, 30-year-old people," Wenger said. "Those cases certainly do occur. Still, however, if you look at [all] invasive group A strep that occurs each year, the vast majority of those occur in people who are elderly or who have some other immunosuppressive illness."
About 80% to 90% of the infections are community-acquired, many appearing as single sporadic cases, he noted. Two deadly community outbreaks struck Virginia and Minnesota last year, resulting in a total of nine deaths. In one, a virulent strain of group A strep prevalent in Virginia's Shenandoah Valley caused 13 persons to become severely ill, two with necrotizing fasciitis. Five of those infected died. In the outbreak in southeast Minnesota, four of seven people infected died.
Reference
1. Valenzuela TD, Hooton TM, Kaplan EL, et al. Transmission of 'toxic strep' syndrome from an infected child to a firefighter during CPR. Ann Emerg Med 1991; 20:90-92. *
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