C.-H. von Bonsdorff

Analysis of Integrated Virological and Epidemiological Reports of Norovirus Outbreaks Collected within the Foodborne Viruses in Europe Network from 1 July 2001 to 30 June 2006

ABSTRACT The Foodborne Viruses in Europe network has developed integrated epidemiological and virological outbreak reporting with aggregation and sharing of data through a joint database. We analyzed data from reported outbreaks of norovirus (NoV)-caused gastroenteritis from 13 European countries (July 2001 to July 2006) for trends in time and indications of different epidemiology of genotypes and variants. Of the 13 countries participating in this surveillance network, 11 were capable of collecting integrated epidemiological and virological surveillance data and 10 countries reported outbreaks throughout the entire period. Large differences in the numbers and rates of reported outbreaks per country were observed, reflecting the differences in the focus and coverage of national surveillance systems. GII.4 strains predominated throughout the 5-year surveillance period, but the proportion of outbreaks associated with GII.4 rose remarkably during years in which NoV activity was particularly high. Spring and summer peaks indicated the emergence of genetically distinct variants within GII.4 across Europe and were followed by increased NoV activity during the 2002-2003 and 2004-2005 winter seasons. GII.4 viruses predominated in health care settings and in person-to-person transmission. The consecutive emergence of new GII.4 variants is highly indicative of immune-driven selection. Their predominance in health care settings suggests properties that facilitate transmission in settings with a high concentration of people such as higher virus loads in excreta or a higher incidence of vomiting. Understanding the mechanisms driving the changes in epidemiology and clinical impact of these rapidly evolving RNA viruses is essential to design effective intervention and prevention measures.

An outbreak of calicivirus associated with consumption of frozen raspberries

In April 1988, an outbreak of gastroenteritis occurred among employees in a large company in Helsinki, Finland. A retrospective cohort study, using a self-administered questionnaire, was carried out to ascertain the cause and extent of the outbreak. To meet the case definition, employees had to have had diarrhoea and/or vomiting since 2 April, 1998. A subanalysis was made in the biggest office, consisting of 360 employees, of whom 204 (57%) completed the questionnaire. Of these 108 (53%) met the case definition. Employees who had eaten raspberry dressing were more likely to meet the case definition than those who had not (Attack Rate (AR) 65% versus AR 18% Relative Risk, (RR) 3.7, 95%, Confidence Intervals (CI) 2.0-6.7). Four stool specimens obtained from affected kitchen staff who had all eaten the raspberry dressing and who had all become ill simultaneously with the employees were positive by polymerase chain reaction (PCR) for calicivirus. The data suggest that the primary source of the outbreak was imported frozen raspberries contaminated by calicivirus.

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.

Short sequences define genetic lineages: phylogenetic analysis of group A rotaviruses based on partial sequences of genome segments 4 and 9

Genetic diversity in strains of human group A rotaviruses was analysed by phylogenetic methods. The study material comprised 109 serotype G1 or G4 rotavirus samples isolated in Finland during 1986-1990. Parts of the coding regions of rotaviral genome segments 4 and 9, which encode proteins with serotype specificity, the spike protein VP4 (P serotype) and the outer capsid protein VP7 (G serotype), respectively, were sequenced. As determined by analysis of segment 4 sequences all G1 strains and all except one G4 strain showed P[8] specificity, the one being of P[6] specificity. The G1P[8] strains could be further differentiated into four groups based on segment 9 sequences, while G4P[8] strains formed only one group. Type P[8] (G1P[8] and G4P[8]) strains formed two main groups based on segment 4 sequences, suggesting free segregation of segment 4 between these G strains. Most global G1, G4 and P[8] strains in GenBank/EMBL originating from the 1970s to the present co-clustered with these groups, suggesting that the groups exist as relatively stable lineages. No linear accumulation of nucleotide substitutions was detected in strains of one serotype during the study period. Also, the deduced amino acids of the antigenic regions A, B and C of VP7 were nearly conserved within the phylogenetic lineages. Interestingly, only short amino acid sequences were necessary to divide the e-types correctly into phylogenetic lineages. These amino acid signature motifs were located in aa 29-68 of VP7 and aa 121-135 of VP4 of the G1 and P[8] lineages, respectively.

The spermatozoon flagella in Diphyllobothrium latum (fish tapeworm)

SummaryThe spermatozoon flagella of the fish tapeworm (Diphyllobothrium latum) is studied. The flagella consist of two axial filament complexes, which represent the unusual nine-plus-one pattern. The inside of the spermatozoon sheath is lined by single filaments. The mechanism of formation of this type of flagella is discussed. The spermatozoon flagella of the flatworms hitherto described seems to show some deviating features as compared with those in other species.

Wading pool water contaminated with both noroviruses and astroviruses as the source of a gastroenteritis outbreak

In July 2001, an outbreak of gastroenteritis occurred in Helsinki among children and adults after bathing in an outdoor wading pool. The epidemiological survey revealed that at least 242 persons were affected. Microbiological testing of both patient stool samples and of the pool water revealed the presence of two different gastroenteritis viruses: a norovirus (NV) and an astrovirus. Amplicon sequencing of the NV samples showed nucleotide sequence identity between the virus from patients and the water. After changing the pool water and the sand at the bottom of the pool followed by shock chlorination, no virus could be detected in the water. However, NV was continuously detected in the water outlet well as much as 8 months after the incident. Here we show how molecular methods aided in tracing the source of the epidemic and in finding the causative pathogens both in patients and in the environment.

Prolonged norovirus outbreak in a Finnish tertiary care hospital caused by GII.4-2006b subvariants

Norovirus outbreaks are difficult to control in hospitals. Cohorting and contact isolation, disinfective surface cleaning and hand hygiene are key elements in outbreak control. A new norovirus variant, GII.4.-2006b, spreading across many continents, caused an exceptionally long epidemic period in Finland, from November 2006 to June 2007. Here, we describe the clinical and molecular characteristics of a norovirus outbreak in a large tertiary care hospital in Finland. Altogether 240 (18%) patients and 205 (19%) healthcare workers fell ill in the 504 bedded main building of Helsinki University Central Hospital during December 2006 to May 2007. The epidemic curve had three peaks in January, February and April, and different wards were affected each time. During the outbreak, 502 patient stool specimens were tested for norovirus RNA, 181 (36%) of which were positive. Molecular analysis of 48 positive specimens revealed three main subvariants of GII.4.-2006b circulating temporally within distinct wards. Of all microbiologically confirmed cases, 121 (67%) were nosocomial and nine (5%) died within 30 days of diagnosis. Molecular analysis suggested that the three main GII.4-2006b subvariants entered the hospital with gastroenteritis patients, and the nosocomial spread within wards coincided with the epidemic peaks. Active control measures, including temporary closure of the wards, ultimately confined the single-ward outbreaks. A prolonged outbreak in the community was probably the source for the prolonged outbreak period in the hospital.

Growth of Rubella Virus in BHK 21 Cells: Electron Microscopy of Morphogenesis

Summary The growth of rubella virus in suspended BHK 21 cells was studied by electron microscopy under conditions of one-step growth. After a latent period of 15 hr the first new virus particles were found with their number increasing successively till about 25 hr. This corresponded well with the infectivity assays obtained from these samples. The virus is formed through two pathways; first, by budding into vesicles of the Golgi-apparatus which then are emptied outside the cells; second, to a lesser extent by budding directly from the marginal cell membrane. No accumulation of nucleoids in the cytoplasm is detected, but they are formed at the site of budding.

Purification of Rubella Virus Particles

Summary A procedure for the purification of rubella virus from infected suspensions of BHK 21 cells resulted in preparations containing 1 to 3 × 1010 p.f.u./ml. In sucrose gradient centrifugation the area of maximal infectivity (buoyant density of 1.175 g./ml.) coincided with peaks in haemagglutinating activity, and in E 260. It also coincided with presence of virus-like particles, and a sharp band visible by naked eye. Specific activities of the order 30 × 106 p.f.u./µg. protein, 106 HAU/µg. protein, and 5 to 10 × 105 p.f.u./HAU were achieved. Glutaraldehyde-fixed negatively stained rubella virus preparations showed round particles with rough surfaces measuring 50 to 73 nm. (average 61 nm.) in diameter. Unfixed viruses had a greater size variation, 55 to 89 nm. (average 74 nm.) in diameter, apparently due to deformability and fragility of the particles. Spontaneous and deoxycholate-induced breakdown of the particles showed rupture of the envelope but revealed no characteristic inner structure.

The flagellar structure of the flame cell in fish tapeworm (Diphyllobothrium latum)

SummaryThe flame cell of the fish tapeworm (Diphyllobothrium latum) is investigated. In cross-section the flagella originating from the flame cell are hexagonal, except the incomplete ones facing the tubular wall. The function, as regards this unusual structure, is discussed. The axial filament complexes in one flame cell are arranged in opposite directions to each other. Thus the flame cell flagella seem to show many deviating characteristics as compared with those hitherto described.