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Biomedical subjects

A D Cliff

Publications and source records attributed to A D Cliff.

14 recordsLinked to original sources
PubMed1999

Spatial and temporal patterns in final amendments to provisional disease counts.

This article examines temporal and spatial patterns in the relationship between provisional and amended reports for Hepatitis A and Hepatitis B received from each state by the Centers for Disease Control and Prevention through the U.S. National Notifiable Diseases Surveillance System from 1980 to 1992. It demonstrates that, as the 1980s unfolded, the preliminary disease reports became less representative markers of final disease counts. Practitioners at the state and community levels need to be aware of the temporal and spatial instabilities in such provisional data if they are used to provide early warning of contemporary health aberrations.

Centers for Disease Control and Prevention, U.S.↗
PubMed1997

The importance of long-term records in public health surveillance: the US weekly sanitary reports, 1888-1912, revisited.

BACKGROUND: This paper outlines the ways in which a little-used archive of early public health records may throw light on longer-term trends in international epidemic behaviour and serve as a major source of epidemiological information for historians of urbanization and public health. The Weekly Abstract of Sanitary Reports was the official disease surveillance report of the US Public Health Service and its predecessors, and began to publish urban mortality statistics on a regular basis in 1888. Here, the authors describe the first 25 years of continuous reporting (1888-1912), when the Reports contained not only disease data for US cities, but also records sent back by US consuls based in some 250 cities in many parts of the world. METHODS: The content of the weekly editions of the Reports was systematically sampled and analysed using graphical techniques and the simple statistical method of running means. RESULTS: Relatively complete weekly series of mortality from all causes, and six infectious diseases (diphtheria, enteric or typhoid fever, measles, scarlet fever, tuberculosis and whooping cough) were identified for a total of 100 cities world-wide. CONCLUSION: Reporting coverage for these cities is sufficiently complete that multivariate analysis should be possible to obtain a comparative picture of mortality for many parts of the world. Despite limitations of the data, sources of the type described in this paper form an important comparative database for studying international patterns of mortality.

Communicable Diseases↗
PubMed1995

The application of multidimensional scaling methods to epidemiological data.

This paper illustrates the use of multidimensional scaling methods (MDS) to examine space-time patterns in epidemic data. The paper begins by outlining the principles of MDS. The model is then formally specified and illustrated by application to two data sets. The first is partly a tutorial example. It uses monthly reported measles morbidity data for the 31-year period from January 1960 to December 1990, collected for the 50 states of the USA, plus New York City and the District of Columbia. These data are used to explore the various ways in which MDS may be used to identify changing spatial patterns in geographically-coded data. In addition to their tutorial use, the data are also employed to search for any substantive changes in the geographical structure of measles epidemics in the USA that may have followed the introduction of mass vaccination in 1965. New England appears to have developed an epidemic profile distinct from the rest of the USA, and there is tentative evidence of an urban-rural split in epidemic characteristics. The second data set takes annual reported measles mortality data for New Zealand and the states of Australia from 1860 to 1949. MDS is used to show how the spatial relationships among these geographical units have changed over time in response to changes in the sizes of local susceptible populations.

Australia↗
PubMed1993

Statistical modelling of measles and influenza outbreaks.

This paper reviews the application of statistical models to outbreaks of two common respiratory viral diseases, measles and influenza. For each disease, we look first at its epidemiological characteristics and assess the extent to which these either aid or hinder modelling. We then turn to the models that have been developed to simulate geographical spread. For measles, a distinction is drawn between process-based and time series models; for influenza, it is the scale of the communities (from small groups to global populations) which primarily determines modelling style. Applications are provided from work by the authors, largely using Icelandic data. Finally we consider the forecasting potential of the models described.

Adolescent↗
PubMed1992

The geographic structure of measles epidemics in the northeastern United States.

The incidence of disease across geographic space often produces distinctive regional patterns. In this paper, a modeling approach to the identification of the factors that shape the patterns is presented, and a procedure for fitting the model to observed data is given. The methodology is illustrated by an application to the geographic structure of measles epidemics among 22 states of the northeastern United States, New York City, and Washington, D.C., from 1962 to 1988. The patterns identified are interpreted in terms of the spatial behavior of measles epidemics in the region, and the implications of the methodology for surveillance and control are considered.

Humans↗
PubMed1992

The changing geographical coherence of measles morbidity in the United States, 1962-88.

Geographical coherence may be defined as the degree to which the behaviour of a time series in one geographical area corresponds with the time series behaviour in another. This paper illustrates the concept using the epidemiological time series of reported monthly measles morbidity for the states of the United States for the 27 years from January 1962 to December 1988. Over this period, as measles morbidity has declined in response to vaccination campaigns, and as the seasonal peaking of the disease in late spring has become less pronounced, the geographical coherence has altered at the national, divisional, regional and state levels. There was a steady decline in coherence from 1962 to 1980. In 1981, a dramatic reduction occurred, but there has been some recovery since. The implications for spatial forecasting models of these reducing levels of coherence are discussed.

Cross-Sectional Studies↗
PubMed1992

Seasonality in tropical AIDS: a geographical analysis.

This paper presents evidence that the growth rate of the AIDS epidemic at the district level in Uganda, Central Africa, displays a seasonally recurring geographical pattern, with epidemic acceleration in some areas of the country in the first 8 months of each year. The spatial and temporal variations in acceleration appear to be correlated with the predominant agricultural systems in different parts of Uganda. Based upon the frequently hypothesized relationship between malnourishment and the progression to clinical AIDS in HIV-infected people, it is suggested that the variations in epidemic speed reflect the seasonal patterns of nutritional deficiency which occur under some tropical agricultural systems. These preliminary findings require further verification since they have important implications for directing nutrition-related remedial responses to the AIDS epidemic in tropical countries where malnutrition and endemic HIV infection coincide.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Civil war and the spread of AIDS in Central Africa.

Using ordinary least squares regression techniques this paper demonstrates, for the first time, that the classic association of war and disease substantially accounts for the presently observed geographical distribution of reported clinical AIDS cases in Uganda. Both the spread of HIV 1 infection in the 1980s, and the subsequent development of AIDS to its 1990 spatial pattern, are shown to be significantly and positively correlated with ethnic patterns of recruitment into the Ugandan National Liberation Army (UNLA) after the overthrow of Idi Amin some 10 years earlier in 1979. This correlation reflects the estimated mean incubation period of 8-10 years for HIV 1 and underlines the need for cognizance of historical factors which may have influenced current patterns of AIDS seen in Central Africa. The findings may have important implications for AIDS forecasting and control in African countries which have recently experienced war. The results are compared with parallel analyses of other HIV hypotheses advanced to account for the reported geographical distribution of AIDS in Uganda.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Forecasting epidemic pathways for measles in Iceland: the use of simultaneous equation and logit models.

Six measles transmission chains between pairs and triplets of medical districts in Iceland are identified using monthly data for the 26 years from 1945 to 1970. The years studied are divided into two halves, a calibration period (1945-1957) and a forecast period (1958-1970). Some simultaneous equation models of the chains are developed and fitted using three-stage least squares. The resulting one month ahead forecasts are presented in terms of the expected case levels and as the probability of epidemics occurring. A single equation probability model using a logistic transformation is then formulated and compared with the simultaneous equation approach. The results obtained from the Icelandic study confirm in practice the advantages theoretically expected from setting up forecasting models containing geographically based chain transmission components.

Disease Outbreaks↗
PubMed1980

Changes in the seasonal incidence of measles in Iceland, 1896--1974.

The changing seasonal patterns of reported measles cases in Iceland during this century are analysed. These changes are related to increased population mobility following the development of external and internal transport links, particularly since 1945. The forging of such links has resulted in a shift in the seasonal distribution of cases from one peculiar to the local social and economic conditions in Iceland to one broadly similar to that in other countries of northern temperate latitudes.

Humans↗