Literature Review
Ray SM, Erdman DD, Berschling JD, et al. Nosocomial exposure to parvovirus B19: Low risk of transmission to healthcare workers. Infect Control Hosp Epidemiol 1997; 18:109-114.
Two sisters, 18 and 19 years old, were admitted to Grady Memorial Hospital, a large public hospital in Atlanta, with sickle-cell disease and parvovirus B19-associated transient aplastic crisis (TAC). They were not isolated because caregivers initially did not recognize the need. Following their hospitalizations and before occurrence of any recognized B19 disease in health care workers, researchers took the opportunity to study the risk of B19 infection in HCWs who cared for those patients and to compare it to HCWs who had no contact with them.
The authors state that their investigation is the first to be prompted by a recognized B19 exposure, instead of a suspected outbreak of B19 disease among personnel.
Patient charts and staffing assignments were reviewed to identify HCWs who entered either patient’s room to provide care prior to isolation. The comparison group was composed of HCWs assigned to areas providing care for adults who had no contact with either patient. Information from HCWs about the type and duration of patient contact, signs and symptoms suggestive of acute B19 infection, and other opportunities for B19 exposure in the community was collected via self-administered questionnaires.
Blood was collected from HCWs when the questionnaire was administered, and serologic testing was performed at the Centers for Disease Control and Prevention. Specimen collection and questionnaire administration occurred seven days to 10 weeks after patient contact. Serologic testing also was performed on patient contacts of the index cases if they had risk factors for adverse outcome of parvovirus infection, such as pregnancy, HIV infection, hemolytic anemia, hematologic malignancy, or recent chemotherapy.
Eighty-seven HCWs (60 from six patient care areas, 21 internal medicine house staff, and six obstetrics house staff) who cared for one of the index patients prior to isolation were identified as potential contacts. The comparison group included 88 HCWs. Seventy-nine (91%) of the exposed HCWs and 86 (98%) of the unexposed HCWs completed a questionnaire and provided a blood sample for testing.
Exposed HCWs did not differ from the comparison group control HCWs in gender or mean age. Exposure to children in the home did not differ between exposed and unexposed HCWs.
Approximately 75% of both exposed and unexposed HCWs reported the presence of at least one symptom (arthralgia, pruritis, rash) on the questionnaire, with no difference in signs or symptoms suggestive of B19 between exposed and unexposed HCWs. Other signs or symptoms present in more than 15% of study participants included malaise, myalgia, headache, sore throat, rhinorrhea, and fever. Malaise and headache were reported significantly more often by exposed workers than by unexposed.
Based on the dates of reticulocytopenia, an eight-day period of probable high-titer viremia was identified for each index patient. Forty-six (58%) of the 79 exposed HCWs had contact with the index patients during those time periods. Serologic results showed that of those 46, 17 (36.9%) were B19 nonimmune. Their rate of recent B19 infection was 5.9% (1/17), which did not differ significantly from the attack rate in the comparison group.
The proportion of immune HCWs did not differ between contact and control groups. "Among nonimmune HCWs, there was no significant difference in the proportion of exposed and unexposed HCWs with B19-specific IgM indicative of recent infection," the researchers state.
They point out that despite two prolonged exposures to the index patients prior to contact isolation, "we were unable to identify any increased risk of nosocomial transmission of B19 to HCWs."
Findings of similar rates of recent infection in exposed and nonexposed HCWs suggest that community risk factors for infection "outweighed the impact of nosocomial exposure in this group of subjects," the authors state. Interestingly, the exposed groups reported more signs and symptoms than the comparison group, "suggesting that awareness and concern about possible exposure may adversely affect the usefulness of using a clinical case definition alone in an investigation of suspected nosocomial B19 transmission."
One reason for the low risk observed in the study could be due in part to the older ages of the index patients, resulting in less likelihood of direct contact with respiratory secretions. The researchers conclude that their findings suggest only a small risk of acquiring B19 infection from nosocomial exposure to adults with TAC. However, too many uncertainties exist to recommend changes in guidelines for isolation of patients with acute or chronic B19 infection. Current recommendations are that patients with TAC or chronic B19 infection be placed in respiratory and contact isolation throughout hospitalization. More specific infection control recommendations might result from studies that identify transmission risks associated with particular patient characteristics and patient care activities.
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