Spatio-temporal data comparisons for global highly pathogenic avian influenza (HPAI) H5N1 outbreaks

Abstract

Highly pathogenic avian influenza subtype H5N1 is a zoonotic disease and control of the disease is one of the highest priority in global health. Disease surveillance systems are valuable data sources for various researches and management projects, but the data quality has not been paid much attention in previous studies. Based on data from two commonly used databases (Office International des Epizooties (OIE) and Food and Agriculture Organization of the United Nations (FAO)) of global HPAI H5N1 outbreaks during the period of 2003-2009, we examined and compared their patterns of temporal, spatial and spatio-temporal distributions for the first time. OIE and FAO data showed similar trends in temporal and spatial distributions if they were considered separately. However, more advanced approaches detected a significant difference in joint spatio-temporal distribution. Because of incompleteness for both OIE and FAO data, an integrated dataset would provide a more complete picture of global HPAI H5N1 outbreaks. We also displayed a mismatching profile of global HPAI H5N1 outbreaks and found that the degree of mismatching was related to the epidemic severity. The ideas and approaches used here to assess spatio-temporal data on the same disease from different sources are useful for other similar studies.

Figure 1. Time series plots of global HPAI H5N1 outbreaks.

Generally speaking, OIE and FAO reflect similar temporal patterns. But, the discrepancies are also obvious in the relatively detailed temporal pattern such as those places highlighted by arrows.

Figure 2. Spatial distribution of global HPAI H5N1 outbreaks.

A high degree of agreement on spatial pattern is obvious between OIE and FAO from a qualitative perspective. However, some minor differences can also be seen such as the middle part of the maps highlighted in arrows.

Figure 3. Spatial distributions of matched and unmatched H5N1 outbreaks for OIE and FAO data.

The spatial distributions of unmatched outbreaks are similar and they are also similar with the distribution of matched outbreaks. This prompts that the general spatial patterns captured by individual OIE and FAO are similar, but the quantitative information recorded by them are different.

Figure 4. Country-based mismatching profile of global HPAI H5N1 outbreaks.

In 2003/2004, the mismatching cases were only located in the Southeast Asia; in 2005 the mismatching outbreaks began to appear in Europe such as Ukraine and Romania; in 2006, the mismatching situations further spread to the Africa and reached a peak from the spatial perspective; in 2007 and thereafter, the mismatching situation began to mitigate gradually. This mismatching profile seems to be consistent with the global epidemic situation of HPAI H5N1 outbreaks.

Figure 5. Results of Spatial-Temporal K-function analysis.

OIE and FAO data have significantly different spatio-temporal distributions because the observed Dst statistic is outside the envelope of 95% confidence interval. When the observed distance is ≤4e+06m, the FAO data is more clustered than OIE data, but more regular than OIE data if the study scale is >4e+06m.