The impact of temperature on the inactivation of enteric viruses in food and water: a review.

Temperature is considered as the major factor determining virus inactivation in the environment. Food industries, therefore, widely apply temperature as virus inactivating parameter. This review encompasses an overview of viral inactivation and virus genome degradation data from published literature as well as a statistical analysis and the development of empirical formulae to predict virus inactivation. A total of 658 data (time to obtain a first log(10) reduction) were collected from 76 published studies with 563 data on virus infectivity and 95 data on genome degradation. Linear model fitting was applied to analyse the effects of temperature, virus species, detection method (cell culture or molecular methods), matrix (simple or complex) and temperature category (<50 and ≥50°C). As expected, virus inactivation was found to be faster at temperatures ≥50°C than at temperatures <50°C, but there was also a significant temperature-matrix effect. Virus inactivation appeared to occur faster in complex than in simple matrices. In general, bacteriophages PRD1 and PhiX174 appeared to be highly persistent whatever the matrix or the temperature, which makes them useful indicators for virus inactivation studies. The virus genome was shown to be more resistant than infectious virus. Simple empirical formulas were developed that can be used to predict virus inactivation and genome degradation for untested temperatures, time points or even virus strains.

Assessment of the stability of human viruses and coliphage in groundwater by PCR and infectivity methods.

AIM: To investigate the potential health hazard from infectious viruses where coliphages, or viruses by polymerase chain reaction (PCR), have been detected in groundwater. Two aspects were investigated: the relationship between infectivity and detection by PCR and the stability of coliphage compared to human viruses. METHODS AND RESULTS: Virus decay (1 year) and detection (2 years) studies were undertaken on groundwater at 12 degrees C. The order of virus stability from most to least stable in groundwater, based on first-order inactivation, was: coliphage PhiX174 (0.5 d(-1)) > adenovirus 2 > coliphage PRD1 > poliovirus 3 > coxsackie virus B1 (0.13 d(-1)). The order for PCR results was: norovirus genotype II > adenovirus > norovirus genotype I > enterovirus. CONCLUSIONS: Enterovirus and adenovirus detection by PCR and the duration of infectivity in groundwater followed similar trends over the time period studied. Adenovirus might be a better method for assessing groundwater contamination than using enterovirus; norovirus detection would provide information on a significant human health hazard. Bacteriophage is a good alternative indicator. SIGNIFICANCE AND IMPACT OF THE STUDY: PCR is a useful tool for identifying the health hazard from faecal contamination in groundwater where conditions are conducive to the survival of viruses and their nucleic acid.

Risk factors, clinical features and genotype distribution of diagnosed hepatitis C virus infections: a pilot for a sentinel laboratory-based surveillance.

Hepatitis C is a global public health problem. A cross-sectional survey was undertaken to determine the frequency of reported risk factors and possible transmission routes in individuals in whom HCV antibody (anti-HCV) was newly detected. Seven public health laboratories in England and Wales reported persons with positive anti-HCV tests over a three-month period (1st November 1996-31st January 1997). A questionnaire was then sent to the clinician or general practitioner (GP) who requested the test. A total of 320 laboratory reports were received from participating laboratories and 221 (69%) questionnaires were received from clinicians and GPs. Of those patients from whom a questionnaire was received (median age 36 years; males 72.9%, females 23.1%), 86% had one or more risk factors for infection reported by the clinician/GP. Injecting drug use (68%) was the main risk factor reported. Reasons for testing included being in a known risk group (65%), liver disease (19%) and blood donation (1.4%). Of the total responders, 67% were asymptomatic, and of those that had had liver function tests 50% were abnormal. The most prevalent HCV genotypes were 3a and 1a. Risk factors for HCV infection can be identified using a simple postal questionnaire to clinicians/GPs who request patient screening.

Correlations between microbial parameters from water samples: expectations and reality.

Data which are collected in order to estimate the correlation between parameters must be analysed with caution. Classical statistics of correlation are often inappropriate. The "r" statistic is very easily distorted by non-Normal data. Non-parametric statistics can be helpful. The interpretation and usefulness of the estimates of correlation will depend on the study plan. If water samples come from disparate sources (e.g. upstream or downstream from sewage outlets) then parameters A and B may occur in their highest and lowest numbers according to how close the samples were to contamination sources thus correlating closely. However, if all samples come from sources with similar pollution levels then plots of A and B will show considerable scatter and apparently little correlation. So what is the relationship between A and B? An example of "perfect" correlation, as demonstrated by replicate counts of a single parameter from split samples, gave an r value of only 0.63 (p = 0.62) due to random variation in numbers of organisms between the two halves of the sample. Thus large amounts of data are needed for studying true correlation because relationships between parameters are embedded in the natural variation. This also illustrated that Standards for a single parameter can be "passed" or "failed" by two halves of the same sample. Study design is clearly of fundamental importance. Consideration must be given to the appropriate way of asking questions about correlation between different parameters.

The detection of small round-structured viruses in water and environmental materials.

A procedure for concentrating small round-structured viruses (SRSVs) (Norwalk-like viruses) from water and other environmental materials is described. Primers based on the helicase region of the SRSV genome were confirmed as specific by reaction with typed specimens, and used to detect virus in concentrates of unseeded and seeded samples. Virus was detected in estuarine recreational water polluted by untreated sewage, although not in seawater samples taken some distance from outfall discharges. It was also detected in river water downstream of a sewage treatment plant. Virus could be detected in all matrices when they were seeded with a positive stool extract, including sewage seeded with as little as 2 microl stool extract, thus confirming the suitability of the method for environmental monitoring.

Management of hospital outbreaks of gastro-enteritis due to small roundstructured viruses.

Small round structured viruses (SRSVs, Norwalk-like viruses, NLVs) are the most common cause of outbreaks of gastro-enteritis in hospitals and also cause outbreaks in other settings such as schools, hotels, nursing homes and cruise ships. Hospital outbreaks often lead to ward closure and major disruption in hospital activity. Outbreaks usually affect both patients and staff, sometimes with attack rates in excess of 50%. For this reason, staff shortages can be severe, particularly if several wards are involved at the same time. SRSVs may be spread by several routes: faecal-oral; vomiting/aerosols; food and water. Viruses may be introduced into the ward environment by any of these routes and then propagated by person-to-person spread. In an outbreak setting, the diagnosis can usually be made rapidly and confidently on clinical and epidemiological grounds, particularly if vomiting is a prominent symptom. By the time an SRSV outbreak has been recognized at ward level, most susceptible individuals will have been exposed to the virus and infection control efforts must prioritize the prevention of spread of infection to other clinical areas bycontainment of infected/exposed individuals (especially the prevention of patient and staff movements to other areas), hand-hygiene and effective environmental decontamination. This report of the Public Health Laboratory Service Viral Gastro-enteritis Working Group reviews the epidemiology of outbreaks of infection due to SRSVs and makes recommendations for their management in the hospital setting. The basic principles which underpin these recommendations will also be applicable to the management of some community-based institutional outbreaks.

The use of reverse transcriptase-polymerase chain reaction to investigate environmental samples for the presence of enteroviruses.

Molecular techniques developed for detection and diagnosis of enteric viruses have been adapted for use with water samples. Although problems of interference and sensitivity remain, reliable and consistent methods should soon be available for the detection in water of enteroviruses, Norwalk-like viruses, and rotavirus.

A pilot study of dried blood spot testing for HIV antibody in neonates.

An unlinked anonymous HIV antibody study of neonates, using surplus dried blood spots on Guthrie cards, was introduced as a means of estimating the prevalence of HIV infection in childbearing women. From March 1990 to February 1992, blood spots from 14,520 infants were tested for anti-HIV, using an HIV IgG antibody capture particle-adherence test; only one sample gave a confirmed positive reaction. This type of study involves no interference in routine care and can be operated without difficulty in a district general hospital setting where neonatal metabolic screening is performed.

Clinically apparent rubella reinfection.

We report two cases of rubella reinfection in apparently immunocompetent young women. In both cases rubella-specific IgG had been detected on two occasions prior to an illness clinically diagnosed as rubella. Rubella-specific IgM was detected by various techniques in samples of serum collected at the time of the illness.

Viruses in sewage as an indicator of their presence in the community.

The results of a three year study of the viruses isolated from sewage by means of five tissue culture types are reported. The enteroviruses identified demonstrated a seasonal pattern which was similar to that of clinical isolates. Echoviruses and coxsackieviruses displayed a changing pattern of dominant serotypes in both sewage and clinical isolates; echovirus 6, 19, 3 and coxsackievirus B4, B5, A9 successively became the most common serotypes. The poliovirus in sewage was all vaccine-like in character. Reovirus, type 2 was abundant; adenovirus, of several serotypes, were the least often identified.