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.

Surveillance of outbreaks of waterborne infectious disease: categorizing levels of evidence.

Public health surveillance requires the monitoring of waterborne disease, but sensitive and specific detection of relevant incidents is difficult. The Communicable Disease Surveillance Centre receives information from various sources about clusters of cases of illness in England and Wales. The reporter may suspect that water consumption or recreational water exposure is the route of infection, or subsequent investigation may raise the hypothesis that water is associated with illness.

Note: development of an external quality assurance scheme for the detection and enumeration of Pseudomonas aeruginosa from water and comparison of results using modified King's A broth and a commercial agar.

Two trials of the isolation and enumeration of a given strain of Pseudomonas aeruginosa from water are reported. In each trial participants received concentrated samples from two batches, one with low and one with high counts, to be diluted to 500 ml in sterile distilled or deionized water and examined for Ps. aeruginosa by membrane filtration.

External quality assessment in water microbiology: statistical analysis of performance.

A UK-based scheme of water microbiology assessment requires participants to record counts of relevant organisms. Not every sample will contain the target number of organisms because of natural variation and therefore a range of results is acceptable. Results which are tail-end (i.

Improved survival from diagnosis of AIDS in adult cases in the United Kingdom and bias due to reporting delays.

Objective: To measure developments in survival patterns among United Kingdom adult AIDS cases.

Design: A follow-up survey of cases reported voluntarily to the national surveillance schemes was undertaken to obtain up-to-date information on vital status.

Methods: All reporting clinicians who had a current AIDS patient not known to have died whose AIDS-defining illness was diagnosed before the end of September 1990 were contacted.

Is risk of Kaposi's sarcoma in AIDS patients in Britain increased if sexual partners came from United States or Africa?

Objective: To determine whether the risk of Kaposi's sarcoma in patients with AIDS is increased by sexual contact with groups from abroad with a high incidence of Kaposi's sarcoma.

Design: Analysis of risk of Kaposi's sarcoma in patients with AIDS, according to country of origin of their sexual partners.

Setting: United Kingdom.

The Stafford outbreak of Legionnaires' disease.

A large outbreak of Legionnaires' disease was associated with Stafford District General Hospital. A total of 68 confirmed cases was treated in hospital and 22 of these patients died. A further 35 patients, 14 of whom were treated at home, were suspected cases of Legionnaires' disease.

A national outbreak of Salmonella typhimurium DT 124 caused by contaminated salami sticks.

An outbreak of Salmonella typhimurium DT 124 infection which affected 101 people in England in December 1987 and January 1988 was detected through surveillance of laboratory reports from medical microbiology laboratories of the NHS and PHLS. Within 1 week of noting the increase in reports, epidemiological and microbiological investigations identified a small German salami stick as the vehicle of infection and the product was withdrawn from sale. The epidemiological investigation highlighted the occurrence of a long incubation period, bloody diarrhoea.

Water quality control trials: statistical tables for direct comparison between membrane filtration bacterial counts and the multiple tube method with a description of the bacteriological method.

Experiments in the quality control of water samples are being conducted in the Public Health Laboratory Service and the water industry in the United Kingdom. The number of distributions which have been made is 7 and 92 laboratories are now participating. The methods used for preparing and distributing samples are described.

Routine surveillance data on AIDS and HIV infections in the UK: a description of the data available and their use for short-term planning.

In the UK surveillance of AIDS and HIV infection is based on routine reporting systems. Whilst attempts are made to ensure that AIDS data are as complete as possible, numbers of reports fluctuate from month to month for reasons which are described. In 1986 there was an increase in death certificates naming AIDS as a cause of death in patients who were not identifiable in the surveillance data.

Surveillance of AIDS in the United Kingdom.

The surveillance of cases of the acquired immune deficiency syndrome (AIDS) in the United Kingdom is described and a preliminary analysis made of the 1012 cases that were reported to the end of August 1987. Homosexuals were the largest risk group. For the first time it is possible to present cases by the date of diagnosis and by the regional health authority of residence.

Most probable numbers of organisms: revised tables for the multiple tube method.

Estimation of numbers of organisms is often made using dilution series, for example when examining water samples for coliform organisms. In this paper the most probable numbers (MPNs) are calculated for a 15-tube series consisting of five replicates at three consecutive tenfold dilutions. Exact conditional probabilities are computed to replace previous approximations.

Statistical analysis of case-control studies of communicable diseases.

At the Communicable Disease Surveillance Centre most outbreak investigations are carried out by questioning cases and unaffected 'controls' to look for associations with possible sources of infection. Illness rates are compared in those exposed with those not exposed to a possible risk factor, using statistical techniques appropriate to the survey design. Significance testing to obtain evidence of the source of transmission is made as quickly as possible so that action may be taken.

An outbreak of shingles?

7 of 101 staff within one department of a large office complex had shingles, as diagnosed by a general practitioner, within a three-month period. This incidence was significantly greater than that in the remaining workforce. Varicella-zoster-specific IgM antibody was detected in all 4 cases from whom early convalescent serum samples were obtained but in none of 22 controls.

Some problems in the prediction of future numbers of cases of the acquired immunodeficiency syndrome in the UK.

The outbreak of the acquired immunodeficiency syndrome in the UK has great implications for health services, and predictions of future numbers of cases have been requested. There is not enough information to make a good estimate of the future epidemic curve, but the trend in new cases can be extrapolated and leads to a predicted number of new cases in the range 460 to 7300 in 1988, with a possible 700 patients from earlier years still alive and needing care at the beginning of 1988.

Routine laboratory reports of patients with acute hepatitis B as indicators of incidence of the disease.

The published results of a 3 year population study of acute viral hepatitis provided an opportunity to assess the completeness of routine reports of laboratory confirmed acute hepatitis B and their validity as indicators of incidence. Similar incidence rates of acute hepatitis B were found in the survey of 1972-1975 in the three London boroughs included in the survey and between 1975 and 1980 in the two regions in which these boroughs are situated. Evidence of bias in the comparison was sought but was not found.

Milk-borne campylobacter enteritis in a rural area.

During November and December 1981 more than 50 residents in a village in Derbyshire had an acute gastrointestinal illness. One month later a second outbreak occurred affecting another 22 people. Campylobacter jejuni was isolated from 12 patients; no other gastrointestinal pathogens were identified.

Excess deaths attributable to influenza in England and Wales: age at death and certified cause.

The multiple regression statistical method has already been used to estimate excess deaths attributable to influenza in England and Wales by winter period. Now we report further studies of deaths by age group and certified cause of death. During the ten winters since the influenza A/Hong Kong (H3N2) virus first arrived (1968/69 to 1977/78) there have been about 120,000 excess deaths.