Control of viral infections in hospitals

Use of genomic analysis of varicella-zoster virus to investigate suspected varicella-zoster transmission within a renal unit

BACKGROUND

The source of hospital-acquired chickenpox infection may be presumed from a known exposure, but has not been previously proven using genomic analysis.

OBJECTIVE

Investigation of suspected VZV transmission was done using single nucleotide polymorphism genomic analysis.

STUDY DESIGN

Comparison was made of viral isolates from two patients with chickenpox on the same ward who were not known to have had direct contact.

RESULTS

An identical genotype in the variable R1 region of the VZV was isolated from the two patients.

CONCLUSION

Inapparent hospital-acquired transmission was the most likely route of infection.

Real-time nested multiplex PCR for the detection of Herpes simplex virus types 1 and 2 andVaricella zoster virus

One hundred forty-nine specimens were tested in a LightCycler nested multiplex polymerase chain reaction (LCnmPCR) for Herpes simplex virus (HSV)1, HSV2, and VZV. Eighty-one were from genitourinary medicine (GUM) patients and the other 68 specimens were from other patients with skin lesions. The results were compared to a conventional multiplex nested PCR (nmPCR) using agarose gel electrophoresis. Twenty-five specimens were positive in both assays for HSV1 and 29 were positive for VZV. For HSV2 there were 27 positive in the LCnmPCR and 26 positive in the nmPCR assay. The melting temperatures (Tms) of each target were different with a mean of 84.75 degrees C for HSV1, 88.57 degrees C for HSV2, and 83.62 degrees C for VZV. The melting curves of positive specimens directly overlaid the melting curves of the positive controls in the assay. The LCnmPCR assay is a convenient alternative to conventional PCR using agarose gel electrophoresis. It improves specimen turnaround time by eliminating the need for gel electrophoresis, transillumination, and gel photography. It also shows increased sensitivity for HSV2 over our standard assay. This LCnmPCR reduces further the possibility of amplicon contamination with nested PCR protocols.

Investigation of an outbreak of gastroenteritis caused by Norwalk-like virus, using solid phase immune electron microscopy

In February 1993, 95 persons (47 patients and 48 staff members) were affected by an hospital outbreak of viral gastroenteritis. Using direct electron microscopy (EM) the causative agent was identified as a small round structured virus. This was confirmed as a Norwalk-like virus using solid phase immune electron microscopy (SPIEM). Of 94 stool samples examined, 12 (13%) samples containing small round structured viruses (SRSV) were SPIEM positive for Norwalk-like virus. A further 25 (27%) samples contained small round featureless virus (SRFV) identified by direct EM and were negative on SPIEM. The illness was characterized by preceding influenza-like symptoms in 76% of cases followed by vomiting (76%), diarrhoea (79%) and abdominal pain (79%). One fatality was recorded. The outbreak lasted for 15 days, with a peak incidence of new cases amongst patients and staff occurring on day 5. It was controlled through a combination of ward closures, patient cohorting, suspension of duties for affected staff and disinfection procedures. Difficulties were encountered in the education of staff and in the implementation of environmental control measures. Screening of hospital catering services and a case control study, carried out among affected staff members, failed to identify a foodborne source. Consumption of tap water in the hospital was commoner among affected staff members than among controls, but this did not reach significance (P = 0.1).

An outbreak due to echovirus type 30 in a neonatal unit in France in 1997: usefulness of PCR diagnosis

Between February and August 1997, 53 patients with enterovirus meningitis were hospitalized in Clermont-Ferrand, France. All but one were children. Echovirus type 30 was involved in 70% of cases with identified serotype. The outbreak ceased on August 8. Two months later, a neonate was admitted to the neonatal unit with an echovirus type 30 meningitis thought to be acquired at delivery. Twenty days later a nosocomial outbreak of echovirus type 30 involving five neonates occurred. Two of them presented with meningitis and two with febrile seizure; One was asymptomatic. The retrospective examination of the maternal sera in a neutralization test, using the index case strain as a source of antigen, showed that none of the neonates was passively immunized before hospitalization. The use of genome detection in cerebrospinal fluid allowed rapid diagnosis and infection was contained by re-inforcing hygiene measures. Prospective examination of stools in the neonatal and paediatric units showed no further occurrences of the disease. No sporadic case was observed in the general population. Hence, nosocomial infections can occur a long time after an outbreak in the general population; rapid diagnosis with molecular tools is useful both for a definite diagnosis in patients already hospitalized, and to act as a rapid alert, even in intervals between seasonal outbreaks.

Rubella immune status among healthcare workers in the Department of Obstetrics and Gynaecology of a regional hospital in Hong Kong: the need for a vaccination policy

Rubella infection in early pregnancy is associated with severe consequences in the developing fetus. In Hong Kong, 8-11% of women of child-bearing age are still susceptible to rubella infection. Therefore, rubella immune status of healthcare workers who may have contact with pregnant women is of particular concern. Rubella immunity of healthcare workers in a Department of Obstetrics and Gynaecology was analysed. In the one and a half years of study, 134 healthcare workers voluntarily submitted blood samples for immunity determination and 16.4% of them were susceptible to rubella infection. A substantial proportion of healthcare workers of childbearing age (14%) was negative for rubella antibody. Susceptible healthcare workers have a risk of acquiring and subsequently transmitting the potentially teratogenic rubella infection to their patients. There is a need to review the rubella immunization policy for healthcare workers in Hong Kong.

Control of varicella-zoster infection on renal and other specialist units

The introduction of chickenpox onto our renal unit recently raised several issues surrounding the management of patient and staff contracts. This paper describes the action taken and makes various recommendations for future management of similar cases. Guidelines are proposed for the management of patients and staff as well as the role of the infection control team in handling a chickenpox problem. Future developments, including the use of VZ vaccine for patient and staff, are also discussed.

An analysis of infection control of varicella-zoster virus infections in Addenbrooke's Hospital Cambridge over a 5-year period, 1987-92

This prospective study analyses infections with varicella-zoster virus (VZV) in Addenbrooke's Hospital, Cambridge during 1987-92 and examines the spread of infection. In total, 93 patients and staff experienced VZV infection. Twenty-one patients had varicella and 49 experienced zoster. None of 101 patients and 1 of 625 staff members in contact with varicella cases acquired infection. By contrast, 2 of 227 patients, and 5 of 1039 staff in contact with zoster cases acquired varicella. One out of 28 (3.6%) VZV antibody-negative patients and staff in contact with varicella acquired infection, compared with 5 out of 29 (17.2%) VZV antibody-negative patients and staff in contact with zoster. Thus, zoster was found to be a more frequent cause of nosocomial infection than varicella. Fourteen members of staff had VZV infection during the study period. One of 99 patients and none of 389 staff members in contact with these cases developed varicella. The cost of dealing with infection control for VZV infections in our hospital is estimated to be Pounds 714 per patient case and a total of Pounds 13,204 per year.

Varicella exposure in a neonatal intensive care unit: emergency management and control measures

We describe an exposure of varicella zoster virus in our neonatal intensive-care unit and the emergency procedures instituted to prevent an outbreak. Fifty-seven infants and 129 staff members were exposed but none developed chickenpox. The measures included rapid identification of varicella antibody status in all neonates and those staff members with uncertain history of varicella infection; cohorting of exposed infants according to immune status; and prompt administration of varicella zoster immunoglobulin to susceptible patients. The recommendation of the American Academy of Pediatrics did not accurately predict the immune status of preterm infants, as only one of the eight susceptible infants would have qualified for immunoglobulin prophylaxis if their guidelines had been followed. Mass screening of all exposed infants using the varicella zoster enzyme linked immunosorbent assay (ELISA) test was the only reliable means of determining the immune status. Of the four risk factors evaluated for the prediction of antibody status: gestational age, postnatal age, birthweight and episodes of blood transfusion, only postnatal age was found to independently predict the immune status of our patients. Because varicella zoster susceptible staff members are difficult to identify on the basis of history, we suggest that prospective screening of staff in high-risk units be undertaken and vaccination with live varicella vaccine be offered to susceptibles.

Viral infections in children's wards--how well do we manage them?

Children are frequently admitted to hospital wards with viral infections. Many are not life-threatening to the index case, but the spread to vulnerable patients who are already at higher risk should be avoided. To do so requires active awareness and availability of rapid diagnosis (i.e. the same day). Cohorting and handwashing have been found to be the best measures to prevent spread of respiratory syncytial virus (responsible for considerable morbidity every winter) in hospital wards.

Control of outbreaks of viral diarrhoea in hospitals--a practical approach

Outbreaks of viral diarrhoea are common in hospitals, particularly in the geriatric and children's wards. Person-to-person spread is the most frequent mode of transmission of infection. Establishment of alerting mechanisms, liaison with laboratories with electron microscopy facilities for making the diagnosis, isolation of patients, use of appropriate disinfectants and maintaining good lines of communication are all important for successful control of these outbreaks.

Molecular technology for hospital epidemiology

Hospital-acquired infections in the United States contribute to approximately 80,000 deaths per year, with an associated cost of > $4 billion. Some of these infections are associated with outbreaks and clusters occurring within the hospital. The hospital infection control team must respond quickly and decisively to recognize and curtail these outbreaks, but their response often depends on critical laboratory data that characterize or "fingerprint" suspected microbial isolates. This presentation summarizes the simple, easily performed tests and the more molecular approaches that a hospital laboratory may take in support of infection control efforts. In addition to phenotypic data, such as biotype and antibiograms, hospitals that elect to incorporate molecular protocols should limit their first experiences to plasmid analysis and plasmid restriction endonuclease profiles.

New laboratory techniques for hospital infection control

The clinical microbiologist has important responsibilities in hospital infection control. Duties include participating in hospital-wide infection control activities (especially the infection control committee), recovering and identifying accurately the organisms responsible for nosocomial infection, characterizing antimicrobial susceptibility of many of these nosocomial pathogens, reporting in timely fashion laboratory data relevant to infection control, carrying out the few routine microbiologic studies of the hospital environment that are useful, supporting investigations of specific hospital infection problems as they arise, and providing special typing studies when necessary to establish similarity or difference of organisms. In the past decade, improvements in laboratory instrumentation and/or procedures have provided dramatic help to infection control efforts in several of these areas. Among these are new techniques for more rapid detection and differentiation of organisms and improved systems of reporting for both patient data and trend analysis. Perhaps the most dramatic advances have come in special procedures for examining (typing) hospital organisms for similarity or difference; here, molecular and other techniques have permitted more definitive examination of a wider range of organisms than previously was possible. With health care resources in the United States now at a premium, the current and future challenge for laboratories is to make their participation in infection control more efficient as well as effective. Establishing adequate quality control of methods and obtaining clinical data to allow correct interpretation will be crucial for efficient use of the new typing procedures. Deciding when these techniques are needed and whether they should be performed on site also will be an important part of this process.