What is Surveillance, Anyway?

Published May 01, 2009 @ 01:39AM PT

One term that comes up a lot when we are talking about epidemics and pandemics is surveillance. The official definition of surveillance is "Disease surveillance is the detection, rapid verification and response to epidemic-prone and emerging disease threats." In its simplest form, surveillance is keeping track of where and when infectious diseases break out. That lets us know what infections are on the rise, and how they are travelling.

We can't, obviously, keep track of every infection that happens everywhere. For one thing, there are plenty of infections you don't go to the doctor for. The common cold, stomach flu, yeast infections. So we can only track infections that lead to contact with the health care system. That being said, we don't track every infection that requires a doctor visit, either. The time and effort of reporting and analyzing all that data wouldn't be worth what we learned from it. There would just be too much to process.

Instead, certain serious diseases are selected for reporting. In the US, these are the Nationally Notifiable Infectious Diseases. They include AIDS, anthrax, rabies, and smallpox. Health care providers in the United States are legally obligates to report any infections on the NNID list. The resulting data is then published in the Morbidity and Mortality Weekly Report. Nearly every country has a similar system of disease reporting, but not all publish the results. The US, like most other countries, then reports its infectious disease data to the World Health Organization in accordance with the International Health Regulations published by the WHO.

There are several places this system runs into trouble. As discussed, people don't always go to the doctor when they are sick. Health care providers may be sloppy about their reporting of infectious diseases, or they may misdiagnose illnesses. This is especially likely when the disease is fatal, and an autopsy is not performed. National governments are often reluctant to share information with WHO that might make them look bad, or they may lack the capacity to collect and report accurate data on an ongoing basis.

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Comments (1)

Thanks for touching on the biosurveillance subject. The current surveillance situation is a little broader than Notifiable Diseases and depends on the methodology used for the surveillance as well as the end purpose of the surveillance.

Most of what you've discussed would fall into a 'direct reporting' capacity used by the national health infrastructure. Separately, there have been attempts at indirect, Syndromic Surveillance - basically looking for indirect indicators of disease in the population. By and large, this has not proven to be effective. Other systems use a methodology of looking at social/societal disruption associated with an outbreak of disease - such things as cancellation of sporting events, festivals, or school closures. This methodology may not be 'disease specific'; however, it has proven to be fairly sensitive. A downside is that one must understand and take cultural perspectives, expectations, and practices into account.

Another point of debate in the biosurveillance community is that regarding purpose of the surveillance system. Traditional monitoring tends to lean toward a true epidemiological approach - it is slow, but you generally get a high degree of specificity. Alternatively, one can take the 'tip off' approach, effectively trading specificity of detection with much more rapid (and sensitive) indication. You might detect that something is happening and have vague descriptions of disease signs, but not a true clinical description.

Each methodology and purpose has it's strengths and weaknesses, and use of the various systems is not mutually exclusive. The questions become: How is each system's reporting used most effectively? How do we make decisions from the gathered data? How do we effectively communicate our conclusions? How do we integrate our surveillance and response methodologies?

Posted by Craig Kiebler on 05/01/2009 @ 11:24AM PT
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Author

Alanna Shaikh has spent the last ten years immersed in global health; she has worked for NGOs, companies, universities, and the US government on projects that ranged from preventing antibacterial resistance to improving maternal and child health.