Rapid contamination with varicella-zoster virus DNA to the throat of a daycare attendee and environmental surfaces from a child with varicella

Occurrence of Human Viruses on Fomites in the Environment: A Systematic Review and Meta-analysis

Documenting the occurrence of viruses on fomites is crucial in determining the significance of fomite-mediated transmission and the potential use of fomites for environmental disease surveillance. We conducted a systematic review and meta-analysis to compile information on the occurrence of human viruses on fomites in the environment; we identified 134 peer-reviewed papers. We compiled sampling and measurement methods, results, quality control information, and whether virus data were compared with community health data from the papers. We conducted univariate and multivariate analyses to investigate if presence of virus on fomites was associated with virus type (enveloped, nonenveloped), sampling location (healthcare setting, nonhealthcare temporary setting, nonhealthcare nontemporary setting), and area of fomite swabbed (<50, 50-100, >100 cm2). Across 275 data sets from the 134 papers, there was the most data available for Coronaviridae and from fomites at hospitals. Positivity rates, defined as the percent positive fomite samples, were low (median = 6%). Data were available on viruses from 16 different viral families, but data on viruses from 9 families had few (n < 5) data sets. Many human virus families were not identified in this review (11 families). Less than 15% of the data sets reported virus concentrations in externally valid units (viruses per area of surface), and 16% provided a quantitative comparison between virus and health data. Virus type and area swabbed were significant predictors of virus presence on fomites, and the positivity rate of data sets collected from healthcare settings and nonhealthcare nontemporary settings (e.g., individual housing) were significantly higher than those collected in nonhealthcare temporary settings (e.g., restaurants). Data from this review indicates that viruses may be present on fomites, that fomite-mediated virus transmission may occur, and that fomites may provide information on circulation of infectious diseases in the community. However, more quantitative data on diverse viruses are needed, and method reporting needs significant improvements.

Communicability of varicella before rash onset: a literature review

Varicella poses an occupational risk and a nosocomial risk for susceptible healthcare personnel and patients, respectively. Patients with varicella are thought to be infectious from 1 to 2 days before rash onset until all lesions are crusted, typically 4–7 days after onset of rash. We searched Medline, Embase, Cochrane Library and CINAHL databases to assess evidence of varicella-zoster virus (VZV) transmission before varicella rash onset. Few articles (7) contributed epidemiologic evidence; no formal studies were found. Published articles reported infectiousness at variable intervals before rash onset, between <1 day to 4 days prior to rash, with 1–2 patients for each interval. Laboratory assessment of transmission before rash was also limited (10 articles). No culture-positive results were reported. VZV DNA was identified by PCR before rash onset in only one study however, PCR does not indicate infectivity of the virus. Based on available medical literature, VZV transmission before rash onset seems unlikely, although the possibility of pre-rash, respiratory transmission cannot be entirely ruled out.

Survival of an Enveloped Virus on Toys

Children's toys may carry respiratory viruses. Inactivation of a lipid-enveloped bacteriophage, Φ6, was measured on a nonporous toy at indoor temperature and relative humidity (RH). Inactivation was approximately 2log10 after 24 hours at 60% RH and 6.8log10 at 10 hours at 40% RH. Enveloped viruses can potentially survive on toys long enough to result in exposures.

Varicella-zoster virus and virus DNA in the blood and oropharynx of people with latent or active varicella-zoster virus infections

Varicella-zoster virus (VZV) can be detected in the blood from approximately 5 days before to 4 days after varicella. VZV DNA, primarily in T-lymphocytes, is detected as early as 8-10 days prior to rash and can persist for a week. The duration and magnitude of VZV DNAemia correlates with immune status and the efficacy of antiviral therapy. VZV DNA is also readily detected in the oropharynx just prior to rash and for 1-2 weeks thereafter. Detection of VZV DNA in blood and saliva has been useful for diagnosis and prognosis in atypical cases of varicella. Herpes zoster (HZ) is also characterized by VZV DNAemia at onset and for many weeks thereafter, and VZV DNA is present in the oropharynx shortly after HZ onset. Detection of VZV DNA in blood and saliva facilitates the diagnosis of zoster sine herpete and other atypical manifestations of VZV reactivation, such as neurologic syndromes when cerebrospinal fluid is not available, Bell's palsy, and atypical pain syndromes. VZV DNA is sometimes present in the blood and saliva of asymptomatic individuals. In total these observations extend understanding of the pathophysiology and epidemiology of VZV, and increasingly contribute to the clinical management of VZV infections.

Comparison of surface sampling methods for virus recovery from fomites

The role of fomites in infectious disease transmission relative to other exposure routes is difficult to discern due, in part, to the lack of information on the level and distribution of virus contamination on surfaces. Comparisons of studies intending to fill this gap are difficult because multiple different sampling methods are employed and authors rarely report their method's lower limit of detection. In the present study, we compare a subset of sampling methods identified from a literature review to demonstrate that sampling method significantly influences study outcomes. We then compare a subset of methods identified from the review to determine the most efficient methods for recovering virus from surfaces in a laboratory trial using MS2 bacteriophage as a model virus. Recoveries of infective MS2 and MS2 RNA are determined using both a plaque assay and quantitative reverse transcription-PCR, respectively. We conclude that the method that most effectively recovers virus from nonporous fomites uses polyester-tipped swabs prewetted in either one-quarter-strength Ringer's solution or saline solution. This method recovers a median fraction for infective MS2 of 0.40 and for MS2 RNA of 0.07. Use of the proposed method for virus recovery in future fomite sampling studies would provide opportunities to compare findings across multiple studies.

Reliability of information on varicella history in preschool children

OBJECTIVE

To verify how reliable is the information provided by parents about the history of varicella in their children.

METHODS

204 parents of previously healthy children attending two municipal day-care centers of São Paulo city were interviewed between August 2003 and September 2005. A standardized form was filled out with information regarding age, sex, history of varicella and other diseases, drug use and antecedent of immunization, After medical history, physical examination and checking of immunization records, 5 ml of blood were collected for ELISA (in house) varicella test. Exclusion criteria were: age less than 1 year or more than 60 months, previous immunization against chickenpox, presence of co-morbidities or recent use of immunosuppressive drugs. Data were filed in a data bank using the Excel 2003 Microsoft Office Program and stored in a PC computer. The exact Fisher test was employed to calculate sensibility, specificity, positive and negative predictive values of history of varicella informed by children's parents.

RESULTS

The age of the children varied from 12 to 54 months (median, 26 months; 49 (24%) children had positive history of varicella, 155 (76%) a negative or doubtful history. The predictive positive and negative values of the information were 90% and 93%, respectively (p = 0.0001).

CONCLUSIONS

The degree of reliability of information about history of varicella informed by parents of children attending day care centers was high and useful to establish recommendations on varicella blocking immunization in day-care centers.

Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

The epidemics of severe acute respiratory syndrome (SARS) in 2003 highlighted both short- and long-range transmission routes, i.e. between infected patients and healthcare workers, and between distant locations. With other infections such as tuberculosis, measles and chickenpox, the concept of aerosol transmission is so well accepted that isolation of such patients is the norm. With current concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. Therefore, the aim of this review is to describe the factors involved in: (1) the generation of an infectious aerosol, (2) the transmission of infectious droplets or droplet nuclei from this aerosol, and (3) the potential for inhalation of such droplets or droplet nuclei by a susceptible host. On this basis, recommendations are made to improve the control of aerosol-transmitted infections in hospitals as well as in the design and construction of future isolation facilities.

Spread of varicella-zoster virus DNA to the environment from varicella patients who were treated with oral acyclovir

OBJECTIVE

The purpose of the present study was to determine the degree of spread of varicella-zoster virus to the environment (VZV) from varicella patients who received oral acyclovir treatment.

METHODS

Over a period of 8 months, seven healthy children (two girls and five boys, 23-64 months of age) with varicella who visited Fujita Health University School of Medicine were treated with routine doses of oral acyclovir (ACV) for 5 days, commencing within 24 h after onset of the disease. Swab samples from the throats of patients and their family members as well as from air purifier filters in their houses were collected for 7 days as frequently as possible after starting treatment for the disease. The VZV DNA in the samples was identified by a sensitive polymerase chain reaction amplification assay.

RESULTS

The VZV DNA was detected in 33-100% of throat swab samples from varicella patients by day 7 of the disease, in 17-32% of throat swab samples from family members by day 4 and in 29% of filters from air purifiers by day 3.

CONCLUSIONS

The results suggest a broad spread of VZV, probably by the airborne route, from the patients with varicella even after the administration of oral ACV.

Detection of varicella-zoster virus DNA in throat swabs of patients with herpes zoster and on air purifier filters

Zoster patients are considered to be less contagious than those with varicella because their infectious lesions are localized. However, it is not known when the spread of varicella-zoster virus (VZV) from zoster patients begins, how long it continues, and how far the virus spreads from the zoster patients. Twelve cases of hospitalized zoster patients were studied. The polymerase chain reaction (PCR) was used to detect VZV DNA in samples taken from the surface of their eruptions, throats, and the air purifier filters in their rooms. In all patients, VZV DNA was detected in the samples from eruptions. VZV DNA was detected in 8 of 12 patients from the throats. VZV DNA was detected for 9 of 12 patients from the filter samples. This study shows the possibility of a wide distribution of VZV DNA to the environment from infected patients. VZV may be excreted from cutaneous eruptions or from the throats of patients.