Global capacity for emerging infectious disease detection

Abstract

The increasing number of emerging infectious disease events that have spread internationally, such as severe acute respiratory syndrome (SARS) and the 2009 pandemic A/H1N1, highlight the need for improvements in global outbreak surveillance. It is expected that the proliferation of Internet-based reports has resulted in greater communication and improved surveillance and reporting frameworks, especially with the revision of the World Health Organization's (WHO) International Health Regulations (IHR 2005), which went into force in 2007. However, there has been no global quantitative assessment of whether and how outbreak detection and communication processes have actually changed over time. In this study, we analyzed the entire WHO public record of Disease Outbreak News reports from 1996 to 2009 to characterize spatial-temporal trends in the timeliness of outbreak discovery and public communication about the outbreak relative to the estimated outbreak start date. Cox proportional hazards regression analyses show that overall, the timeliness of outbreak discovery improved by 7.3% [hazard ratio (HR) = 1.073, 95% CI (1.038; 1.110)] per year, and public communication improved by 6.2% [HR = 1.062, 95% CI (1.028; 1.096)] per year. However, the degree of improvement varied by geographic region; the only WHO region with statistically significant (α = 0.05) improvement in outbreak discovery was the Western Pacific region [HR = 1.102 per year, 95% CI (1.008; 1.205)], whereas the Eastern Mediterranean [HR = 1.201 per year, 95% CI (1.066; 1.353)] and Western Pacific regions [HR = 1.119 per year, 95% CI (1.025; 1.221)] showed improvement in public communication. These findings provide quantitative historical assessment of timeliness in infectious disease detection and public reporting of outbreaks.

Fig. 1.

Geographical distribution of a subset of outbreaks confirmed and reported by WHO, 1996–2009. Points mark the reported origin of the outbreak, or if unknown, where the highest reported morbidity and mortality rates were reported. (World borders dataset downloaded from http://thematicmapping.org/.)

Fig. 2.

Box plots of the median time between estimated outbreak start and various outbreak milestones for a subset of WHO-confirmed outbreaks, 1996–2009. Public communication refers to the earliest date of the public being informed about the existence of cases. WHO report refers to the date of WHO's Disease Outbreak News report about the outbreak. Some extreme outliers are not shown. n, sample size.

Fig. 3.

Box plots of the temporal trends in the yearly median time between estimated outbreak start and (A) outbreak discovery and (B) public communication about the outbreak for selected WHO-verified outbreaks, 1996–2009. The revised International Health Regulations (IHR 2005) went into effect in 2007.

Fig. 4.

Box plots of the median time difference from estimated outbreak start to outbreak discovery and public communication about the outbreak for selected WHO-verified outbreaks,1996–2009, across various WHO regions. Extreme outliers are not shown.

Fig. 5.

A sensitivity analysis where serial Cox proportional hazards regression analyses were performed to determine the hazard ratio comparing the hazard for (A) outbreak discovery and (B) public communication about the outbreak before and after a cutoff date that was sequentially changed to June 15 of each year from 1997 to 2008. WHO's revised International Health Regulations (IHR 2005) officially went into force on June 15, 2007.

Fig. 6.

The exclusion criteria applied in selecting a subset of WHO-confirmed outbreaks reported in Disease Outbreak News (1996–2009). A single report may describe more than one outbreak, and may fall under more than one exclusion criterion category.