Kenneth W Cross

Mortality in children from influenza and respiratory syncytial virus

Study objective: To quantify mortality attributable to influenza and respiratory syncytial virus (RSV) infection in children. Design and methods: Comparison of death rates (all cause and certified respiratory) in England over winters 1989/90 to 1999/00 during and outside influenza and RSV circulation periods. Virus active weeks were defined from clinical and virological surveillance data. Excess deaths associated with weeks of either influenza or RSV activity over virus non-active weeks were estimated in each winter for age groups 1–12 months, 1–4, 5–9, and 10–14 years. The estimate obtained was allotted to influenza and RSV in the proportion derived from independent separate calculations for each virus. Main results: Average winter respiratory deaths attributed to influenza in children 1 month–14 years were 22 and to RSV 28; and all cause deaths to influenza 78 and to RSV 79. All cause RSV attributed deaths in infants 1–12 months exceeded those for influenza every year except 1989/90; the average RSV and influenza attributed death rates were 8.4 and 6.7 per 100 000 population respectively. Corresponding rates for children 1–4 years were 0.9 and 0.8 and for older children all rates were 0.2 or less, except for an influenza rate of 0.4 in children 10–14 years. Conclusions: Influenza and RSV account for similar numbers of deaths in children. The impact varies by winter and between age groups and is considerably underestimated if analysis is restricted to respiratory certified deaths. Summing the impact over the 11 winters studied, compared with influenza RSV is associated with more deaths in infants less than 12 months, almost equal numbers in children 1–4 years, and fewer in older children. Improved information systems are needed to investigate paediatric deaths.

Gender difference in the incidence of shingles.

We investigated age- and gender-specific incidence of shingles reported in a large sentinel practice network monitoring a defined population over the years 1994-2001. In total, 5915 male and 8617 female incident cases were studied. For each age group, we calculated the relative risk of females to males presenting with shingles. Incidence rates of chickenpox and herpes simplex were examined similarly. Shingles incidence was greater in females in each age group (except for 15-24 years). Relative risks (female to male) were greatest in age groups 45-64 years (1.48) and 0-14 years (1.43). There were no gender differences in the incidence of chickenpox except in the 15-24 years age group (female excess): for herpes simplex there were female excesses in all age groups. Gender-specific age-standardized incidence rates of shingles were calculated for each year and showed a consistent female excess in each of the 8 years (average annual excess 28%).

The incidence of shingles and its implications for vaccination policy

A vaccine is now available to prevent varicella-zoster infection, but its place in routine preventive care is not yet determined. The age specific incidence of shingles was examined separately by gender and age groups (15-24, 25-44, 45-64, 65-74 and 75 years and more) over the years 1994-2001. These incidence data were applied to national available data for the UK on current life expectancy to calculate the risk of shingles infections at varying ages. The potential benefit of an effective vaccine was estimated using three models of vaccine efficacy applied separately to males and females at ages 50, 60 and 65 years and assuming vaccination at a single age. Similar calculations were made using a two dose strategy at age 45 and 65 years and at age 50 and 70 years. The cost per case saved was estimated from a vaccination cost of pound 40 per dose. The probability of having had an attack of shingles before age 45 years is 8.6% for males and 10.5% for females, The risk of acquiring shingles over an expected lifetime (assuming no preventive vaccination) for males aged 45 years is 22% and for females 32%. Whichever vaccine efficacy model was chosen, a single vaccination policy at age 65 years was the most favourable option in both males and females. A two age vaccination policy was estimated to increase the cost per case saved by 30% over a single age policy but administration at age 50 and 70 years substantially increased the number of cases saved as compared with a single age policy and was potentially better than vaccination at 45 and 65 years.

Seasonality and trends in the incidence and prevalence of gout in England and Wales 1994–2007

Objectives: To examine seasonality and long-term trends in the incidence and prevalence of gout. Methods: A retrospective study (1994–2007) using routinely collected surveillance data from the Royal College of General Practitioners Weekly Returns Service sentinel general practice network in England and Wales. New cases and acute attacks of gout per 10 000 population were calculated for age groups 0–44, 45–64, 65–74 and ⩾75 years. Long-term trends of annual incidence were assessed by regression analysis. Seasonality indices were calculated using 4-weekly data, and the relative risk of gout incidence during the summer was estimated. Annual prevalence was estimated from the consulting patient population (2001–7) and from prescribing data on defined daily doses (DDD) of allopurinol (2003–7). Results: The annual incidence rate of new gout cases was stable over the period 1998–2007; acute attacks decreased on average 4% per annum. New gout cases and acute attacks combined into 4-weekly incidence rates peaked during the “summer” period of each year. There was an increased risk of gout diagnosis during summer months (late April to mid-September; odds ratio 1.22, 95% CI 1.18 to 1.26). The annual prevalence of gout in 2001–7 was 0.46%, with highest rates in men ⩾75 years (2.57%). Estimated prevalence based on a DDD of 400 mg allopurinol was 0.37%. Conclusion: The incidence of gout is seasonal. This has implications for the management of patients who currently have gout, and for those who are at risk of future attacks. The decreasing trend in the incidence of acute attacks suggests that patient management is improving.

Influenza and its relationship to circulatory disorders

Three sources of data (general practice episode data from the Weekly Returns Service of the Royal College of General Practitioners, national hospital admission data for England and national mortality data by date of death) were examined separately in each winter (1994/1995 to 1999/2000) to investigate the impact of influenza on circulatory disease. Weekly data on incidence (clinical new episodes) hospital emergency admissions and deaths certified to circulatory disorders and to respiratory diseases (chapters VII and VIII of ICD9) during influenza epidemic periods (defined from combined clinical/virological surveillance) were examined in age groups 45-64, 65-74 and > or =75 years. Data collected in the four winters in which there were substantial influenza A epidemics were consolidated for the period 6 weeks before to 6 weeks after each peak of the epidemic, and associations between the variables at different time lags examined by calculating cross-correlation coefficients. We also examined deaths due to ischaemic heart disease (IHD) as a proportion of all circulatory deaths and deaths due to influenza/pneumonia as a proportion of all respiratory deaths. There were no increases of GP episodes nor of emergency admissions for circulatory disorders in any of the three age groups during epidemic periods. Increased circulatory deaths occurred in all age groups and particularly in the oldest group. The large cross-correlation coefficients of deaths (circulatory and respiratory) with GP respiratory episodes at weekly lags of 0, -1 and 1 were evidence that the deaths and episode distributions were contemporaneous. The ratios of excess circulatory deaths relative to excess respiratory deaths during epidemic periods were 0.74 (age 45-64), 0.72 (65-74) and 0.57 (> or =75 years). Increased circulatory deaths contemporary with new incident cases of respiratory episodes but with no concomitant increase in admissions suggests rapid death during the acute phase of illness. Influenza contingency planning needs to take account of these deaths in determining policy for prophylaxis and in providing facilities for cardio-respiratory resuscitation.

The incidence of molluscum contagiosum, scabies and lichen planus.

We aimed to describe the incidence of new episodes of molluscum contagiosum, scabies and lichen planus presenting to general practitioners in England and Wales. We examined data collected in a sentinel practice network (the Weekly Returns Service of the Royal College of General Practitioners) in which about half a million persons were observed each year over the period 1994-2003. The incidence of molluscum contagiosum in males was 243/100,000 person-years and in females 231; of scabies, males 351, females 437; of lichen planus, males 32, females 37. Incidence varied by year and age. Ninety per cent of molluscum contagiosum episodes were reported in children aged 0-14 years, where incidence in 2000 (midpoint of a 6-year period of stable incidence) was 1265/100,000 (95% CI 1240-1290). Scabies affected all ages and annual incidence ranged between 233 (95% CI 220-246) in 2003 and 470 (95% CI 452-488) in 2000. Lichen planus occurred chiefly in persons aged over 45 years: incidence (all ages) ranged between 27 (95% CI 23-31) in 2003 and 43 (95% CI 37-49) in 1998. The relative risk of female to male incidence (all ages) of molluscum contagiosum was 0.95 (95% CI 0.91-0.99); of scabies 1.25 (95% CI 1.21-1.28); and of lichen planus 1.19 (95% CI 1.08-1.13).

Morbidity profiles of patients consulting during influenza and respiratory syncytial virus active periods

We compared the burden of illness due to a spectrum of respiratory diagnostic categories among persons presenting in a sentinel general practice network in England and Wales during periods of influenza and of respiratory syncytial virus (RSV) activity. During all periods of viral activity, incidence rates of influenza-like illness, bronchitis and common cold were elevated compared to those in baseline periods. Excess rates per 100,000 of acute bronchitis were greater in children aged <1 year (median difference 2702, 95% CI 929-4867) and in children aged 1-4 years (994, 95% CI 338-1747) during RSV active periods rather than influenza; estimates for the two viruses were similar in other age groups. Excess rates of influenza-like illness in all age groups were clearly associated with influenza virus activity. For common cold the estimates of median excess rates were significantly higher in RSV active periods for the age groups <1 year (3728, 95% CI 632-5867) and 5-14 years (339, 95% CI 59-768); estimates were similar in other age groups for the two viruses. The clinical burden of disease associated with RSV is as great if not greater than influenza in patients of all ages presenting to general practitioners.

Acute respiratory infections and winter pressures on hospital admissions in England and Wales 1990–2005

BACKGROUND Hospitals experience winter surges in admissions due to respiratory infections. The roles of acute bronchitis and influenza-like illness (ILI) in the timing and severity of these surges are examined over the years 1990-91 to 2004-05. METHODS Respiratory admissions of persons aged > or =65 years in England and Wales were analysed in relation to patients with ILI or acute bronchitis diagnosed by community-based general practitioners from a sentinel surveillance network. RESULTS Acute bronchitis and ILI accounted for 46 and 7% of the variation in respiratory admissions, respectively: when admissions were lagged by 1 week, these estimates were 20 and 14%, respectively. Admissions peaked in weeks 52, 01 or 02 (late December to early January) in 14 of the 15 winters. Acute bronchitis peaked during weeks 01 or 02; ILI exhibited greater variability and peaks ranged from weeks 46 (mid-November) to 07 (mid-February). During winters where acute bronchitis and ILI peaked concurrently, surges on hospitals were most severe. CONCLUSIONS During each winter acute bronchitis provides a consistent and major contribution to the winter admissions surge in the elderly. The variable incidence of ILI can increase the surge in admissions, especially when ILI and acute bronchitis peak together.

The problem of diagnostic variability in general practice.

STUDY OBJECTIVE--The aim was to examine the scale, source, and relevance of variation between general practices in respect of the rates with which patients consulted with illnesses falling in each of several diagnostic groups. DESIGN--This study involved a general practice morbidity survey conducted over two years, 1970-72. All patients who consulted their general practitioners were identified and the number of these who consulted with diagnoses attributable to each of the 18 main chapters of the International classification of diseases were counted. Patients who consulted for more than one diagnosis within a chapter were counted once only; those who consulted for one or more diagnoses in each of several chapters were counted once for each chapter. SETTING--This was a national survey involving general practitioners in England and Wales. SUBJECTS--The study involved 214,524 patients from 53 selected general practices (115 doctors) who were registered with their general practitioners for the whole of the year 1970-71 and for whom their morbidity data had been linked with their social data from the 1971 census. MEASUREMENTS AND MAIN RESULTS--Using the numbers of patients on the practice lists as denominators, practice patient consulting rates (PPCR) were calculated for each practice and for each ICD chapter. Variability in chapter PPCR was examined by calculating coefficients of variation and, after allowance for random variation, coefficients of residual variation. There were large interpractice (doctor) variations in all chapter rates. These variations were only marginally attributable to: chance; different age, sex and social class mixes of practice populations; geographical locations; and practice organisation. The rates were, however, consistent from one year to the next for any one practice. Approximately half of the interpractice (doctor) diagnostic variability was associated with overall patient consulting behaviour. When the effects of this behaviour were discounted, any major residual diagnostic variability was confined largely to ICD chapters I-V, XVI, and XVII, ie, those chapters where aetiology forms the basis of classification. CONCLUSION--Variations in recorded diagnostic rates are mainly due to the consistent but idiosyncratic and selective exclusion by practitioners of some components from the total set which often coexist in a new diagnosis. Because of the scale of interpractice diagnostic variability, the use of algorithms and information technology is largely precluded from outcome studies, auditing procedures, and studies of practice work loads in general. However, (1) the consistency of any individual doctors pattern of diagnostic recording from one year to another permits studies of trends; and (2) given a reasonable number of recording practices, the population mean practice consulting rates can be estimated with sufficient accuracy for many epidemiological research and administrative uses.

The consistency of shingles and its significance for health monitoring

Accurate estimation of monitored populations is essential for epidemiological study. Many countries do not have systems of patient registration and routine disease surveillance is thereby hindered. We studied the incidence of shingles over time and investigated the hypothesis that the incidence is consistent and could be used as a proxy for estimating the monitored population. Annual incidence rates of shingles reported in the Weekly Returns Service (WRS) since 1970 and in the Dutch Sentinel Network (DSN) over the period 1998–2001 were studied. Gender specific annual rates (1998–2001) were compared after standardising for age. The population in the DSN was estimated by applying the WRS incidence rates to the numbers of DSN incident cases. The incidence of shingles was annually and seasonally consistent. Incidence in males was similar in both networks and in females approximately 18% greater in the WRS: in age groups 15–64 years, incidence was similar in both networks, but in children 0–14 years and in persons 65 years and over, it was higher in the WRS. The total populations in the DSN estimated from average age/gender specific rates in the WRS were within 12% of the observed in each of the 4 years surveyed. The incidence of shingles in the two countries was sufficiently close to estimate the surveyed population aged 15–64 years from knowledge of incident cases in the community. Routine monitoring of shingles in sentinel practice networks is commended as a method of assuring recording quality and as a means of estimating the survey population where the registered population is not known.