Widespread environmental contamination with Norwalk-like viruses (NLV) detected in a prolonged hotel outbreak of gastroenteritis

A protracted outbreak of Norwalk-like virus (NLV)-associated gastroenteritis occurred in a large hotel in North-West England between January and May 1996. We investigated the pattern of environmental contamination with NLV in the hotel during and after the outbreak. In the ninth week, 144 environmental swabs taken from around the hotel were tested for NLV by nested RT-PCR. The sites were categorized according to the likelihood of direct contamination with vomit/faeces. The highest proportion of positive samples were detected in directly contaminated carpets, but amplicons were detected in sites above 1.5 m which are unlikely to have been contaminated directly. The trend in positivity of different sites paralleled the diminishing likelihood of direct contamination. A second environmental investigation of the same sites 5 months after the outbreak had finished were all negative by RT-PCR. This study demonstrates for the first time the extent of environmental contamination that may occur during a large NLV outbreak.     

A school outbreak of Norwalk-like virus: evidence for airborne transmission

An outbreak of gastroenteritis affected a school attended by children aged 4-11 years. Epidemiological features suggested this was due to Norwalk-like virus (NLV) and this was confirmed by polymerase chain reaction (PCR). Nucleotide sequence analysis of the PCR amplicons revealed identical strains in all five positive stool samples. Pupils were significantly more likely to become ill following an episode of vomiting within their classroom (adjusted odds ratio 4.1, 95% CI 1.8-9.3). The times from exposure to illness were consistent with direct infection from aerosolized viral particles where exposure to vomiting was high. Cleaning with quaternary ammonium preparations made no impact on the course of the outbreak. However, the outbreak stopped after the school closed for 4 days and was cleaned using chlorine-based agents. This study confirms the importance of vomiting in the transmission of NLV and provides evidence that direct infection with aerosolized viral particles occurs.     

Molecular epidemiology of Norwalk-like virus (NLV) outbreaks occurring in Kyushu Japan between 1988 and 1993

In nine outbreaks that occurred in the Kyushu district between 1988 and 1993, we determined the nucleotide sequences of Norwalk-like virus (NLV) gene fragments amplified by RT-PCR and molecular-epidemiologically analyzed the NLV epidemics. It is known that the NLV strains isolated from nine outbreaks of acute gastroenteritis, were divided into five clusters consisting of two genogroups. Described by the year of outbreaks, the genogroup-1 (Norwalk-like virus group) was prevalent in 1988, 1989, and 1992, the genogroup-2 (snow mountain-like virus group) was detected in 1988, 1989, and 1993. Especially it was revealed that various strains of NLV were prevalent in the Kyushu district from 1988 to 1989. Epidemics of the Norwalk-like strain continued to be prevalent in 1992 (FP/7/92), and the strains very close to OSAP 18 continued to be prevalent in 1993 (FP/8/93, FP/9/93). Although the strains belonging to Norwalk virus (KY89) in the genogroup-1 and belonging to P1B (OSAP 18) in the genogroup-2 were detected for a prolonged period from 1988 to 1992/1993, the homology in these strains was very close, and this study shows that a high homogeneity was conserved in these strains. It was revealed that various strains of NLV were prevalent in the Kyushu district from 1988 to 1989.     

A prolonged outbreak of Norwalk-like calicivirus (NLV) gastroenteritis in a rehabilitation centre due to environmental contamination

An outbreak of Norwalk-like calicivirus (NLV) gastroenteritis occurred in a rehabilitation centre in southern Finland between December 1999 and February 2000. An epidemiological investigation was conducted to determine the source and extent of the outbreak. More than 300 guests and staff members became ill during the outbreak. No food or activity in the centre could be linked epidemiologically to illness. NLV genogroup II was detected by RT-PCR in stool samples of symptomatic guests and employees. All strains reacted similarly with the microplate hybridization probe panel and showed the same nucleotide sequence, indicating that they represented the same NLV strain. Food and water samples were negative for NLV, whereas NLV was detected in three environmental specimens. The strains from patients and environment were identical based on microplate hybridization probes, suggesting that environmental contamination may have been important for the spread of calicivirus and the protracted course of the outbreak.     

A large hotel outbreak of Norwalk-like virus gastroenteritis among three groups of guests and hotel employees in Virginia

A large outbreak of acute gastroenteritis occurred among three different groups of guests and the employees of a Virginia hotel within a 2-week period in November 2000. At least 76 of the hotel's guests and 40 hotel employees had acute gastroenteritis during this period. All tested ill persons were infected with the same strain of Norwalk-like virus, as shown by cloning and sequencing of virus detected in stool specimens from the three guest groups and the employees. Epidemiologic investigation suggested food as the probable source for the guests. Most of the employees, including those sick, did not eat in the hotel, suggesting that environmental contamination and person-to-person transmission could have contributed to the outbreak. The disease continued to spread in the hotel, passing from one guest group to another, by food, environmental contamination, and/or by person-to-person transmission through infected employees and guests. The study describes procedures implemented to control the outbreak and makes recommendations for future outbreak control.     

Evidence for insect transmission of rabbit haemorrhagic disease virus

The spread of rabbit haemorrhagic disease (RHD) virus from quarantine on Wardang Island to mainland Australia in 1995 suggested that insects could be potential vectors. Field observations and laboratory experiments were conducted to address aspects of this hypothesis. Firstly, the variation in insect populations on the island during the field trials was examined. There was approximately a 1,000-fold increase in the number of bushflies, Musca vetustissima, shortly before the spread of the virus. Secondly, M. vetustissima were tested in the laboratory as potential vectors of RHD virus, and it was demonstrated that disease could be transmitted between rabbits by flies. Finally, 13 of 16 insect samples, collected from Wardang Island and from several sites on the mainland following the spread of virus off the island, were positive for the presence of RHD virus by a specific polymerase chain reaction (PCR). Only one sample contained sufficient infectious virus to kill a susceptible rabbit. These data, combined with previously published information on fly biology, suggested that flies, particularly bushflies, may be involved in the transmission of RHD virus. Other possible routes of spread were not assessed in this study.     

Practical lessons from the management of an outbreak of small round structured virus (Norwalk-like virus) gastroenteritis

An outbreak of viral gastroenteritis caused illness in 92 people during October 2000. All the cases had an association with one hotel and 80% of cases identified had attended one of two buffet meals on 18th October 2000. Cohort analysis did not implicate any particular foodstuff in this outbreak. All bacteriological tests on food samples were negative. Small round structured virus (SRSV)/Norwalk-like virus (NLV) particles were seen by electron microscopy in 6 out of 27 stool samples submitted for analysis. This paper describes the outbreak and in particular the lessons learned from the management and control of it. These include practical points with regard to the outbreak control team, liaison with the microbiology laboratory, handling data, agreeing a case definition, and occupational health issues. All can be applied elsewhere by those responsible for managing outbreaks at a local level.     

Waterborne outbreak of Norwalk-like virus gastroenteritis at a tourist resort,Italy

In July 2000, an outbreak of gastroenteritis occurred at a tourist resort in the Gulf of Taranto in southern Italy. Illness in 344 people, 69 of whom were staff members, met the case definition. Norwalk-like virus (NLV) was found in 22 of 28 stool specimens tested. The source of illness was likely contaminated drinking water, as environmental inspection identified a breakdown in the resort water system and tap water samples were contaminated with fecal bacteria. Attack rates were increased (51.4%) in staff members involved in water sports. Relative risks were significant only for exposure to beach showers and consuming drinks with ice. Although Italy has no surveillance system for nonbacterial gastroenteritis, no outbreak caused by NLV has been described previously in the country.     

A foodborne outbreak of Norwalk virus gastroenteritis. Evidence for post-recovery transmission

From November 10-16, 1982, 220 (57%) of 383 attendees at eight banquets for which food had been prepared at a single hotel restaurant and the employees of the hotel had onset of Norwalk virus gastroenteritis. Epidemiologic investigation of the three largest banquets confirmed consumption of potato and fruit salads (banquet A), coleslaw (banquet B), and tossed salad (banquet C) to be significantly associated with illness. Between November 8-19, similar illness occurred in seven (54%) of 13 hotel kitchen employees. The foods implicated in banquets A and B were prepared by one salad worker during her acute illness and up to 48 hours following her recovery. A second salad worker prepared the implicated tossed salad for banquet C 24 hours following her recovery. To the authors' knowledge, this is the first foodborne outbreak investigation demonstrating Norwalk viral excretion and transmission by a food handler after recovery from illness and either person-to-person or vehicle-borne transmission between food handlers with subsequent transmission by more than one food handler to patrons.     

An outbreak of food-borne gastroenteritis in two hospitals associated with a Norwalk-like virus.

Two connected outbreaks of gastroenteritis in separate hospitals associated with a small round structured virus morphologically indistinguishable from the Norwalk virus are described. The virus was most probably introduced on chicken sandwiches prepared by a member of the kitchen staff who was incubating the disease.     

High time for a total ban on smoking in the hotel, restaurant and catering industry: the arguments are mounting

Active and passive smoking are well-known causes of disease, including respiratory and cardiovascular disease and cancer. In 2004 the Dutch government introduced new legislation to regulate smoking in the workplace. However, smoking is still allowed in hotels, bars and restaurants, despite the fact that two-thirds of the Dutch population support a total ban on smoking in public places. Several other European countries and American states have banned smoking in public places. Studies performed in these regions show that the new smoking regulations have had no negative economic effects. Moreover, various studies have shown that smoking bans have a positive impact on public health, even in the short-term, including a significant decrease in respiratory and cardiovascular disease. There is therefore no reason to continue to exclude hotels, bars and restaurants from the smoking ban in all public places in The Netherlands.     

25- to 30-nm virus particle associated with a hospital outbreak of acute gastroenteritis with evidence for airborne transmission

Between November 1 and 22, 1985, an outbreak of acute, nonbacterial gastroenteritis occurred in a 600-bed hospital in Toronto, Ontario, Canada. Illness in 635 of 2,379 (27%) staff was characterized by fatigue, nausea, diarrhea, and vomiting and had a median duration of 24-48 hours. The finding of virus-like particles measuring 25-30 nm in six stool specimens and low rates of seroresponse to Norwalk virus (3/39) and Snow Mountain agent (1/6) suggest that a Norwalk-like virus was responsible for the outbreak. The outbreak was of abrupt onset and high incidence, affecting 79 people in a single day. No common food or water exposure could be identified. The attack rate was greatest (69%) for staff who had worked in the Emergency Room. Of 100 patients and their companions who visited the Emergency Room on November 11-12 for unrelated problems, 33 (33%) developed gastroenteritis 24-48 hours after their visit, versus 0 of 18 who visited the Emergency Room on November 8 (p less than 0.001). An analysis of housekeepers who worked at least once during the period from November 9-13, which included those who became ill during the period of November 9-14, showed that the risk of becoming ill was four times greater for those who visited or walked through the Emergency Room than for those who did not (p = 0.028). These data are consistent with the possibility of the airborne spread of a virus.     

Influence of maternal human immunodeficiency virus (HIV) co-infection on vertical transmission of hepatitis C virus (HCV): a meta-analysis

BACKGROUND: Maternal co-infection with human immunodeficiency virus (HIV) has been implicated as a potentially important co-factor for enhanced vertical transmission of hepatitis C virus (HCV). In previous reports, however, methodological issues (notably small sample sizes) have limited accurate evaluation of the contribution of maternal co-infection with HIV on the risk of vertical transmission of HCV. METHODS: A systematic review and subsequent meta-analysis of current published and unpublished reports was performed. Odds ratios (OR) and 95% CI for individual studies were calculated with maternal HIV serostatus as the exposure measure and HCV vertical transmission as the outcome measure. Overall summary estimates were then calculated using a random effects model that estimates a weighted average of OR from individual studies. RESULTS: In total, 2382 infants from 10 studies were included in an analysis of HCV-infected mothers (defined by anti-HCV+ antibody assays) with and without concomitant HIV infection. The risk estimate (OR) of HCV vertical transmission was 2.82 (95% CI: 1.78-4.45; P = 0.00001) from anti-HCV+/HIV+ co-infected mothers compared with anti-HCV+/HIV- mothers. In a subanalysis of 1327 infants born to viraemic (HCV RNA+) mothers, the risk estimate of HCV vertical transmission was 1.97 (95% CI: 1.04-3.74; P = 0.04) from HCV viraemic/HIV+ co-infected mothers compared with HCV viraemic/HIV- mothers. CONCLUSIONS: Results from this meta-analysis of observational studies suggest that the risk of HCV vertical transmission is higher in infants born to HIV co-infected mothers.     

儿童诺瓦克样病毒感染临床特征及危险因素

目的了解儿童诺瓦克样病毒（Norwalk—like virus，NLVs）感染的临床特征及危险因素。方法收集临床诊断为病毒性腹泻患儿的粪便标本并填写调查表。对收集的标本分别采用ELISA检测轮状病毒（Rotavirus，RV）、RT-PCR检测NLVs。对调查表资料采用1：1配对病例（NLVs）一病例（RV）及1：1配对病例对照研究，分析NLVs感染的临床特点及危险因素。结果648份标本中检出RV339份（52．31％），NLVs80份（12．35％）。分析表明，NLVs所致腹泻的临床特征有别于RV腹泻。前者最早出现呕吐症状者居多（62．82％），并且有呕吐症状者多于后者。而RV腹泻患儿最早出现的症状以腹泻为主（65．38％）。发热、最高温度、发热天数、腹泻天数、是否输液治疗及就诊次数均为RV感染患儿高于NLVs感染患儿。对NLVs腹泻可能的危险因素进行单因素及多因素条件Logistic回归分析，最终筛选出4项危险因素。分别为吃生冷食品、与腹泻患者接触、吮手习惯及较少洗手。结论NLVs是导致儿童腹泻的重要病原体。其所致腹泻的临床特征不同于RV腹泻；RV腹泻临床症状较NLVs腹泻严重，但NLVs腹泻所造成的家庭经济负担不容忽视。