Legionella longbeachae detected in an industrial cooling tower linked to a legionellosis outbreak, New Zealand, 2015; possible waterborne transmission?

A legionellosis outbreak at an industrial site was investigated to identify and control the source. Cases were identified from disease notifications, workplace illness records, and from clinicians. Cases were interviewed for symptoms and risk factors and tested for legionellosis. Implicated environmental sources were sampled and tested for legionella. We identified six cases with Legionnaires' disease and seven with Pontiac fever; all had been exposed to aerosols from the cooling towers on the site. Nine cases had evidence of infection with either Legionella pneumophila serogroup (sg) 1 or Legionella longbeachae sg1; these organisms were also isolated from the cooling towers. There was 100% DNA sequence homology between cooling tower and clinical isolates of L. pneumophila sg1 using sequence-based typing analysis; no clinical L. longbeachae isolates were available to compare with environmental isolates. Routine monitoring of the towers prior to the outbreak failed to detect any legionella. Data from this outbreak indicate that L. pneumophila sg1 transmission occurred from the cooling towers; in addition, L. longbeachae transmission was suggested but remains unproven. L. longbeachae detection in cooling towers has not been previously reported in association with legionellosis outbreaks. Waterborne transmission should not be discounted in investigations for the source of L. longbeachae infection.

Epidemiological investigation of a Legionnaires' disease outbreak in Christchurch, New Zealand: the value of spatial methods for practical public health.

Between April and August 2005 Christchurch, New Zealand experienced an outbreak of Legionnaires' disease. There were 19 laboratory-confirmed case including three deaths. Legionella pneumophila serogroup 1 (Lpsg1) was identified as the causative agent for all cases. A case-control study indicated a geographical association between the cases but no specific common exposures. Rapid spatial epidemiological investigation confirmed the association and identified seven spatially significant case clusters. The clusters were all sourced in the same area and exhibited a clear anisotropic process (noticeable direction) revealing a plume effect consistent with aerosol dispersion from a prevailing southwesterly wind. Four out of five cases tested had indistinguishable allele profiles that also matched environmental isolates from a water cooling tower within the centre of the clusters. This tower was considered the most probable source for these clusters. The conclusion would suggest a maximum dispersal distance in this outbreak of 11·6 km. This work illustrated the value of geostatistical techniques for infectious disease epidemiology and for providing timely information during outbreak investigations.

Changing epidemiological trends of legionellosis in New Zealand, 1979-2009.

This study evaluated the spatio-temporal variation of Legionella spp. in New Zealand using notification and laboratory surveillance data from 1979 to 2009 and analysed the epidemiological trends. To achieve this we focused on changing incidence rates and occurrence of different species over this time. We also examined whether demographic characteristics such as ethnicity may be related to incidence. The annual incidence rate for laboratory-proven cases was 2·5/100,000 and 1·4/100,000 for notified cases. Incidence was highest in the European population and showed large geographical variations between 21 District Health Boards. An important finding of this study is that the predominant Legionella species causing disease in New Zealand differs from that found in other developed countries, with about 30-50% of cases due to L. longbeachae and a similar percentage due to L. pneumophila for any given year. The environmental risk exposure was identified in 420 (52%) cases, of which 58% were attributed to contact with compost; travel was much less significant as a risk factor (6·5%). This suggests that legionellosis has a distinctive epidemiological pattern in New Zealand.

An outbreak of Pontiac fever due to Legionella longbeachae serogroup 2 found in potting mix in a horticultural nursery in New Zealand.

Previous outbreaks of Pontiac fever have invariably been associated with water droplet spread of Legionella spp. In January 2007 three workers from a horticultural nursery were admitted to hospital with non-pneumonic legionellosis. Investigations showed that a working party of ten people had been exposed to aerosolized potting mix; nine of these workers met the case definition for Pontiac fever. The presence of genetically indistinguishable Legionella longbeachae serogroup 2 was demonstrated in clinical specimens from two hospitalized workers and in the potting mix to which they had been exposed. A further seven cases were diagnosed by serological tests. This is the first documented outbreak of Pontiac fever from L. longbeachae serogroup 2 confirmed from inhalation of potting mix. Pontiac fever is likely to be under-diagnosed. We advocate the introduction of an industry standard that ensures the use of face masks when handling potting mix and attaching masks and warning labels to potting mix bags sold to the public.

Evaluation of a home-delivery service for HIV-infected patients attending an inner London HIV treatment centre.

Home delivery (HD) of medication is a goal of the Department of Health's Pharmacy in the Future; Implementing the NHS Plan. We evaluated the safety and effectiveness of an HD service for antiretroviral therapy (ART). Patients on ART with stable viral load (VL) <50 were identified. Comparison was made between patients using HD and those using the clinic-based pharmacy (CP). The primary endpoint was HIV virological failure (VF) (HIV VL >400 copies/mL on two consecutive occasions). Secondary endpoints included frequency of outpatient attendances (OPA) and an incidence of adverse events. Cumulative incidences (CulmIn) for each outcome event were calculated. Incidence-rate ratios (IRR) were obtained using Poisson regression. Of 1663 patients identified; 450 received HD and 1213 used CP. CuImIn of VF was =4% in those using HD and =7% in those using CP (IRR [95% confidence intervals, CI] =0.53, 0.32-0.90). HD patients had fewer OPA, less frequent blood test monitoring and less frequent abnormal liver function results (IRR [95% CI]= 0.63 [0.59-0.67] and 0.59 [0.53-0.67], 0.68 [0.65-0.71] and 0.64 [0.53-0.78], respectively). Patients deemed stable enough on social, psychological and medical grounds to receive HD of ART had a lower risk of VF, fewer OPA and no increase in adverse events when compared with patients using CP.

Milk amyloid A: correlation with cellular indices of mammary inflammation in cows with normal and raised serum amyloid A.

This study compared concentrations of amyloid A in bovine milk with the cell-based indicators of intramammary inflammation, somatic cell count and California Mastitis Test. Mammary quarter data pertaining to 180 cows were categorised according to concentrations of serum amyloid A in the cow of origin. Ranked correlation, ranked regression and receiver operator characteristics all demonstrated acceptable agreement between milk amyloid A concentrations and cell-based indices. There were some indications of reduction in this agreement, in cows with raised concentrations of serum amyloid A. However, there were also indications that serum amyloid A did not significantly influence milk amyloid A. The results of the current study indicate that milk amyloid A exhibits good correlation with established cell-based indicators of intramammary inflammation.

Investigation of the prevalence of Legionella species in domestic hot water systems.

AIMS: To investigate the prevalence of Legionella spp. in the hot water systems of a representative sample of Wellington domestic residences with electrically heated hot water systems, and to investigate risk factors (eg water temperature, plumbing materials) for such contamination. METHOD: 100 households with electrically heated hot water systems in the Wellington area were investigated. Samples of hot water from several hot water outlets were collected, and characteristics of the plumbing system were recorded. Water samples and swabs were cultured and further examined by polymerase chain reaction (PCR) and direct fluorescence antibody (DFA) testing to identify Legionella spp. and serogroups. RESULTS: No Legionella spp. were isolated by culture. PCR tested positive for Legionella in specimens from twelve residences. Six of these were also positive by DFA testing. The only environmental factor found to be associated with the presence of Legionella was recent plumbing work on the hot water system. Five of the twelve PCR-positive residences, and four of the six DFA-confirmed residences had hot water delivery temperatures in excess of 60 degrees C. CONCLUSIONS: The results suggest that either Legionellae colonise domestic hot water reticulation systems and/or that the organisms are killed during passage through the hot water tank. Both possibilities may be correct. Further work to characterise the microbial ecology of Legionella-positive hot water distribution systems would be useful, as would the development of improved methods for culturing the organisms from potable water.

Cumulative incidence of hepatitis C seroconversion in a cohort of seronegative injecting drug users.

AIM: To measure the cumulative incidence of hepatitis C virus seroconversion over a two year period in a group of seronegative injecting drug users. METHODS: The study involved follow-up, in 1996, of a cohort (n=85) of injecting drug users identified as hepatitis C virus seronegative in 1994. Participants were interviewed about risk factors for hepatitis C. A blood sample was also taken for anti-hepatitis C virus antibody and hepatitis C virus RNA testing. RESULTS: Forty-four participants were interviewed and 39 gave blood for testing. Most (80%) were aged 29 years or under and two thirds (n=26) were male. Around half reported borrowing (49%) or lending (57%) needles and syringes since 1994 and both of these behaviours were associated with seroconversion. The majority (88%) also reported sharing other injecting equipment. Nine were anti-hepatitis C virus positive giving a seroconversion rate over two years of 23% (13 per 100 person years). Four out of the nine seropositive specimens tested were also hepatitis C virus RNA positive. CONCLUSIONS: This study demonstrates a high rate of recent hepatitis C virus seroconversion amongst a group of New Zealand injecting drug users. Transmission of hepatitis C virus appears to be unabated by current control measures. These findings confirm the need to develop more effective policy and practices to prevent further spread, not just of hepatitis C, but of other blood-borne viruses in injecting drug user populations.

Children's self-talk under conditions of mild anxiety.

Two studies are described which used think-aloud (Study 1) and verbal thought-listing (Studies 1 and 2) procedures to assess preadolescent children's self-talk under conditions of mild anxiety. The self-talk reported was coded into six theoretically meaningful categories and the relationship between self-talk type and anxiety (state and trait) examined. Increased levels of anxiety were associated with higher rates of negative self-talk, but not clearly associated with other types of self-talk. These results suggest negative self-talk plays a role in the generation or maintenance of anxiety in normal children. From the data, it is unclear to what extent perceived task difficulty contributes to the relationship between trait anxiety and negative self-talk. Assessment of self-regulation (Study 1) identified higher levels of anxiety in children reporting awareness of strategies for managing their anxiety.

The Grand Rapids dip revisited.

This analysis addresses an issue that has concerned road safety authorities for some 28 years: the celebrated "Grand Rapids Dip." This, most readers will recognise, is the below-baseline excursion, which occurs in the blood alcohol concentration (BAC) interval of .01%-.04%, of the relative risk curve for accident risk versus blood alcohol, derived from the 1964 Grand Rapids Study data. The present analysis has its starting place in the explanation advanced by Allsop, who noted that the case/control comparisons were biased due to the disproportionate representation of demographic subgroups in different blood alcohol concentration class intervals. Indeed, when relative-risk curves are derived separately for subgroups of differing drinking habits, the resulting separate risk curves all show monotonic increases at all blood alcohol concentration ranges. Such separate relative risk curves are unpopular, and most of the road safety community pays them little heed. Thus, the original concept of the "dip" remains with us. For this reason, we have derived, using a simple but realistic statistical model, a single relative-hazard curve from the Grand Rapids data, one that is free from the distortion introduced by unequal representation of different demographic subgroups in different blood alcohol concentration class intervals. This curve indicates that accident risk increases with increased blood alcohol concentration regardless of self-reported drinking frequency. However more frequent drinkers have less risk at all blood alcohol concentration levels, including zero, than less frequent drinkers at the times and places sampled.

The safety implications of some control changes at urban intersections.

Injury accident data for a sample of New Zealand urban intersections were analysed, looking for an increase or decrease which coincided with a change in control. Increases or decreases were also looked for in certain types of accidents and in accident severity. The control changes considered were from give way signs, stop signs and no control to signals and small roundabouts and also from no control to give way and stop signs.

Four variables affecting magnitude of dentrifice abrasiveness.

A five-factor study was done on human dentin abrasion that involved two abrasives, either alone or in dentifrice form, two brush brands, two brush hardnesses, two concentrations, and two temperatures of testing. The hard brushes caused 3.6 times as much wear as the soft brushes, a greater influence than the abrasives compared. A brush X hardness interaction indicated that there is a wide variation among the stiffness gradings of toothbrushes. Tests run at 37 C were 28% less abrasive than those at room temperature, suggesting a softening of bristles because of the warmer temperature. A highly significant abrasive X concentration interaction showed that dentifrices became more than twice as abrasive on dilution form 100 to 50%, but that abrasives alone did not show such changes on dilution. The second study included two hardnesses, two abrasives, three diluents, four concentrations, and two replicates. An interaction was found between abrasive and diluent, showing that glycerine inhibited abrasion by 88% in comparison with saliva and CMC. A hardness X concentration interaction showed that wear varied widely with concentration for the hard brush but scarcely at all for the soft brush. These findings suggest that abrasiveness of dentifrices depends strongly on testing conditions and that no single set of conditions is suitable for evaluating dentifrice abrasiveness.

Underestimation of length by subjects in motion.

To check a prior observation, in the present experiment, subjects made estimates of the lengths of both the guidelines and the spaces between guidelines on automotive highways so the magnitude of the illusion could be more accurately determined. Ten males and ten females were individually tested at 0 and 60 mph. At 60 mph, spaces were estimated with an error of 85%; lines were estimated with an error of 72%. Combining data for both stimuli, an error of 78% results, which corresponds to underestimation by a factor of 4.67. This illusory effect is considerably greater than that of the moon illusion, considered by many the most powerful of the classical illusions.

Effect of toothbrush variables on wear of dentin produced by four abrasives.

A study was conducted to explore the effect of brush brand, brush hardness, and the concentration of abrasive on the wear of human dentin by four dentifrice abrasives. The two hard brushes produced similar and high levels of abrasion, whereas the two medium brushes of the same brands gave dissimilar and lower levels of abrasion. Dilution changed the ranking of two of the four abrasives.