WHO offers standards to improve global flu surveillance

Robert Roos

Jul 19, 2012 (CIDRAP News) – Largely as a result of gaps in global influenza surveillance that were exposed during the 2009 pandemic, the World Health Organization (WHO) has released a set of standards designed to improve the collection and use of flu data around the world.

Historically, flu surveillance has focused chiefly on virologic monitoring and collecting specimens to guide selection of strains for vaccines, the WHO says. In contrast, the new standards focus mainly on the collection, reporting, and analysis of epidemiologic data on seasonal flu.

The WHO recently posted the 68-page draft document, titled WHO Interim Global Epidemiologic Surveillance Standards for Influenza, on its Web site. It is inviting comments on the guidelines until Oct 31, after which they will be revised and published in final form.

The report says recent years have brought a growing awareness of the need to gather more epidemiologic data to complement the virologic data collected by the WHO Global Influenza Surveillance and Response System through its 130-plus national influenza centers. The 2009 pandemic revealed specific surveillance deficiencies that hindered the assessment and monitoring of the event. In particular, it says:

The lack of surveillance for severe disease in most countries and the resulting absence of historical data limited governments' ability to gauge the pandemic's severity.
The lack of an existing international mechanism for sharing epidemiologic data created obstacles to understanding global patterns of transmission and disease.
Varied approaches to data collection and outbreak investigations early in the pandemic produced findings that were often incompletely understood outside their local context.

During the 2009 pandemic, the WHO was accused of exaggerating the severity of the situation. Critics mainly in Europe argued that pharmaceutical companies looking to profit from the sale of antivirals and vaccines unduly influenced the agency to declare the outbreak a pandemic. That controversy is not specifically mentioned in the new report, however.

The WHO says that standardizing flu data collection will "enable national policy makers to better understand risk factors for severe disease, the variation of influenza severity from season to season and its relationship to virus types or subtypes, the burden of disease related to influenza, and other factors critical to public health decision-making."

The basic underlying principle of the standards is that countries should monitor "both mild and severe disease related to influenza, using appropriate laboratory methods to confirm the presence of influenza," the document states, adding that using consistent case definitions is essential.

The report provides a list of 11 objectives or functions for which timely, high-quality flu data are needed. Some examples are:

Signaling the start and end of the flu season
Identifying and monitoring groups at high risk for severe disease
Establishing baseline levels of activity for flu and severe flu-related disease in order to measure the impact and severity of each flu season
Helping to develop an understanding of the relationship of virus strains to disease severity
Monitoring antiviral sensitivity
Facilitating vaccine strain selection

"Not all of these objectives will be accomplished by every system, particularly when resources are limited," the WHO says. "For example, not every system will describe the genetic makeup of circulating viruses or test for antiviral sensitivity, except when participating in regional and global networks."

The document presents standards for "a minimal basic respiratory disease surveillance system" for monitoring flu and provides a surveillance framework that governments can adapt to their own health resources. The guidelines do not "require countries to dramatically alter existing respiratory disease surveillance systems but rather to establish minimum standards for inpatient and outpatient respiratory disease surveillance reporting, data collection, and analysis."

The WHO takes pains in the report to explain that the recommended surveillance standards are not designed for rapid detection of novel flu strains or other novel respiratory diseases. It states, "Events that call for rapid response for containment or mitigation require detection at a very early stage when the event is geographically localized and involves a relatively small number of people. As such, they require a very sensitive detection system that uses methods different from those used in routine data collection."

The report includes chapters on, among other topics, case definitions, selection and location of sentinel sites, case selection and sampling strategy, lab testing, data collection and reporting, defining baselines and thresholds, using a routine surveillance system in a pandemic situation, and legal issues.

In addition, appendices offer sample data-collection forms, examples of weekly and annual surveillance reports, and other resources.

The standards are the product of a series of discussions and meetings that began in 2010 and included a global consultation in Geneva in March 2011, according to the report. The guidelines are based on a careful review of the available data and have undergone "limited field testing," the report states.