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. Of these about 82% were estimated to be in those aged 65+ years, 17% in the 40-64 year age group and 1% in younger adults. Sixty-seven per cent were certified as due to respiratory disease and 31% due to circulatory system disease. Respiratory deaths increased in all age groups during an epidemic, but of the deaths certified as due to circulatory disease, cerebrovascular deaths were mostly in the 65+ age group and ischaemic heart disease deaths in the 40-64 year age group. In this 40-64 year age group there was evidence that the effects of cold weather and epidemic influenza were multiplicative rather than additive. During the worst influenza winter of 1969/70 respiratory deaths increased by approximately 55% and circulatory system deaths by 4%. Deaths in the elderly increased by 10%, in those aged 40-60 years by 8% and in younger adults by 4%. There was no evidence that excess deaths are followed by a deficit during the following year.
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. It is difficult to prove beyond reasonable doubt that such a hypothesis is correct. Water samples from the time of exposure are seldom available, some organisms are difficult to detect and almost everyone has some exposure to water. Therefore, we have developed a method of categorizing the degree of evidence used to implicate water. The categories take into account the epidemiology, microbiology and water quality information. Thus outbreaks are classified as being associated with water either 'strongly', 'probably' or 'possibly'. This system allows a broad database for monitoring possible effects of water and is not confined to the few outbreaks which have been intensively investigated or have positive environmental microbiology. Thus, for reported incidents, the sensitivity of classifying it as water associated should be high but this may be at the expense of specificity, especially with the 'possible' association.
SUMMARYA 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. All these patients had visited the hospital during April 1985. Epidemiological investigations demonstrated that there had been a high risk of acquiring the disease in the out patient department (OPD), but no risk in other parts of the hospital. The epidemic strain ofLegionella pneumophila, serogroup 1, subgroup Pontiac la was isolated from the cooling water system of one of the air conditioning plants. This plant served several departments of the hospital including the OPD. The water in the cooling tower and a chiller unit which cooled the air entering the OPD were contaminated with legionellae. Bacteriological and engineering investigations showed how the chiller unit could have been contaminated and how an aerosol containing legionellae could have been generated in the U–trap below the chiller unit. These results, together with the epidemiological evidence, suggest that the chiller unit was most likely to have been the major source of the outbreak.Nearly one third of hospital staff had legionella antibodies. These staff were likely to have worked in areas of the hospital ventilated by the contaminated air conditioning plant, but not necessarily the OPD. There was evidence that a small proportion of these staff had a mild legionellosis and that these ‘influenza–like’ illnesses had been spread over a 5–month period. A possible explanation of this finding is that small amounts of aerosol from cooling tower sources could have entered the air–intake and been distributed throughout the areas of the hospital served by this ventilation system. Legionellae, subsequently found to be of the epidemic strain, had been found in the cooling tower pond in November 1984 and thus it is possible that staff were exposed to low doses of contaminated aerosol over several months.Control measures are described, but it was later apparent that the outbreak had ended before these interventions were introduced. The investigations revealed faults in the design of the ventilation system.
SUMMARYAn outbreak ofSalmonella typhimuriumDT 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. Prompt recognition and investigation of the outbreak prevented further cases of severe infection.
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