Systematic Review of Surveillance Systems for Emerging Zoonotic Diseases

The purpose of this review is to synthesize available evidence for public health practitioners, making decisions in the event of emerging zoonosis, by finding public health surveillance initiatives for emerging zoonosis and seeing what criteria have been used to evaluate these systems.

Emerging infectious diseases (EIDs) can be broadly defined as having newly appeared in a population or rapidly increasing in incidence or geographic range; numbers have increased globally over the past 50 years. Estimates of the proportion of EIDs that involve pathogens transmitted from animals to humans, or zoonosis, range from 60% to 75%.

There has been a proliferation of surveillance systems for various diseases over the past 50 years, with many more geared towards EIDs in the past decade. This includes “syndromic surveillance” which loosely refers to collection of “new” data types that are not diagnostic of a disease but might indicate the early stage of an outbreak. There are published recommendations for evaluating various types of surveillance systems available; minimal attention has been placed on whether or not EID surveillance requires a different set of criteria for design and evaluation.

Few surveillance systems (17) were evaluated in the peer-reviewed literature and only four of these used the results to examine the usefulness of their systems for detection of disease. Three of four evaluations concluded that the system was useful because it identified the chosen outbreak of disease; one concluded that it was not useful because it did not identify the chosen outbreak. Of six evaluations, “surveillance of health events” reported in the non-peer-reviewed literature as part of the Canadian Field Epidemiology Program (CFEP), only three featured true surveillance systems. All the CFEP reports contained evaluations of selected systems, often using multiple evaluation criteria which varied depending on system attributes, data availability, and specific objectives of each evaluation. The most common evaluation criterion was timeliness, followed by acceptability, utility, and relevance.

The term ‘surveillance’ is used differently in veterinary and human public health literature. Animal health surveillance is often much more passive, since the collection and reporting of animal disease and zoonotic disease in animals is not legally mandated to the same extent, particularly in wildlife. Although neither human nor animal agencies currently have a clear mandate to compare animal and human disease data in an integrated fashion, such a mandate would be instrumental in developing and sustaining these efforts. Surveillance for zoonosis is a multi-disciplinary endeavor, including environmental health and public health practice and policy. Collaboration of these fields is even more important for emerging zoonotic disease surveillance, as identification of new diseases draws on reports from various types of practitioners on the front lines, public health professionals, and researchers. Current trends are to integrate human and animal data in one surveillance initiative.

Recommendations: Government agencies and epidemiology training programs should encourage publication of surveillance evaluation reports in the peer-review literature; there should be further research in the science of surveillance, which needs to be studied, defined, and standardized; and systems should include evaluation. The role of public health inspectors in emerging zoonotic surveillance is unclear; those setting up such systems should contemplate their inclusion.