Surveillance of measles in Scotland 1983-1991; a comparison of statutory notification and laboratory reporting

Stochastic modeling of empirical time series of childhood infectious diseases data before and after mass vaccination

The goal of this paper is to analyze the stochastic dynamics of childhood infectious disease time series. We present an univariate time series analysis of pertussis, mumps, measles and rubella based on Box-Jenkins or AutoRegressive Integrated Moving Average (ARIMA) modeling. The method, which enables the dependency structure embedded in time series data to be modeled, has potential research applications in studies of infectious disease dynamics. Canadian chronological series of pertussis, mumps, measles and rubella, before and after mass vaccination, are analyzed to characterize the statistical structure of these diseases. Despite the fact that these infectious diseases are biologically different, it is found that they are all represented by simple models with the same basic statistical structure. Aside from seasonal effects, the number of new cases is given by the incidence in the previous period and by periodically recurrent random factors. It is also shown that mass vaccination does not change this stochastic dependency. We conclude that the Box-Jenkins methodology does identify the collective pattern of the dynamics, but not the specifics of the diseases at the biological individual level.

[Measles, pertussis, rubella and mumps completeness of reporting. Literature review of estimates for industrialized countries]

BACKGROUND

Surveillance data for infectious diseases in industrialized countries have been providing useful epidemiological information for several years. However, surveillance is complex and notifications underestimate the true disease incidence. The goal of this paper is to determine the completeness of reporting of measles, pertussis, rubella and mumps through notification in industrialized countries.

METHODS

A thorough literature review of papers published (in French or English) on surveillance data of measles, pertussis, rubella and mumps was undertaken with PUBMED. The review was limited to studies conducted in industrialized countries that quantitatively assessed the completeness of the reporting of these diseases.

RESULTS

Fourteen studies published from the 1920s met the inclusion criteria. For measles, the studies suggest that 64-85% of symptomatic patients sought medical care, 13-57% of those were diagnosed with measles and 22-81% of the diagnosed cases were reported for a completeness of reporting ranging from 7% to 63% between 1920 and 1980 and 3% to 41% in recent years. For pertussis, it was estimated that 49-59% of symptomatic patients sought medical care, 12% of those were diagnosed and 19-47% of the diagnosed cases were reported for a completeness of reporting ranging from 5% to 25% between 1920 and 1980 and from 3% to 12% in recent years. Very few studies on rubella and mumps were found and none allowed the determination of the global completeness of reporting.

CONCLUSION

Reporting has been found to be considerably incomplete. Continued efforts to improve the recognition and reporting of these diseases are needed.

Scaling properties of childhood infectious diseases epidemics before and after mass vaccination in Canada

The goal of this paper is to analyse the scaling properties of childhood infectious disease time-series data. We present a scaling analysis of the distribution of epidemic sizes of measles, rubella, pertussis, and mumps outbreaks in Canada. This application provides a new approach in assessing infectious disease dynamics in a large vaccinated population. An inverse power-law (IPL) distribution function has been fit to the time series of epidemic sizes, and the results assessed against an exponential benchmark model. We have found that the rubella epidemic size distribution and that of measles in highly vaccinated periods follow an IPL. The IPL suggests the presence of a scale-invariant network for these diseases as a result of the heterogeneity of the individual contact rates. By contrast, it was found that pertussis and mumps were characterized by a uniform network of transmission of the exponential type, which suggests homogeneity in the contact rate or, more likely, boiled down heterogeneity by large intermixing in the population. We conclude that the topology of the network of infectious contacts depends on the disease type and its infection rate. It also appears that the socio-demographic structure of the population may play a part (e.g. pattern of contacts according to age) in the structuring of the topology of the network. The findings suggest that there is relevant information hidden in the variation of the common contagious disease time-series data, and that this information can have a bearing on the strategy of vaccination programs.