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FluAid Special Edition: Questions and Answers

November 30, 2009, 12:00 PM ET

What is the difference between FluAid 2.0 and FluAid Special Edition software?

The national influenza pandemic plan (HHS Pandemic Influenza Plan) calls for each state to develop its own state-specific plan for dealing with an influenza pandemic, but to do so, public health planners need to have estimates of the potential impact of a pandemic in their state or locality. To determine these estimates, the Centers for Disease Control and Prevention (CDC) has developed two software programs—FluAid 2.0 and FluAid Special Edition—that can be used to estimate the impact of a flu pandemic before interventions are applied—that is, they illustrate what could happen without public health interventions and are intended solely as a guide to help plan and prepare for an influenza pandemic. Specifics of the two software programs follow.

FluAid 2.0 (http://www.cdc.gov/flu/tools/fluaid/) contains, as default values, data from the 1968 pandemic. Thus FluAid 2.0 provides estimates of the potential impact from a 1968-type pandemic. It is also possible, using a set of instructions available on the CDC Web site (http://www.cdc.gov/flu/pandemic/pdf/pandemic-impact-estimate-instructions.pdf), to use FluAid 2.0 to estimate the potential impact of a 1918-type pandemic.

FluAid Special Edition (http://www.cdc.gov/h1n1flu/tools/fluaidse) was developed to provide estimates of the potential impact of 2009 H1N1 in the 2009–10 influenza season. FluAid Special Edition provides a user with estimates of the probable total number of cases, and the number (as a range) of hospitalizations, deaths, and outpatient visits that could result from the 2009 H1N1 pandemic. FluAid Special Edition can also be used to estimate the percentage, by age group, of people with pre-existing chronic medical conditions* that could be impacted. The percentage of those with pre-existing chronic medical conditions is based on an analysis of data collected during the 2007 National Health Interview Survey (http://www.cdc.gov/nchs/nhis.htm).

* NOTE: Chronic medical conditions are those pre-existing medical conditions (e.g., emphysema, asthma, diabetes) such that, should a person with one or more of such conditions contract a clinical case of influenza, they are more likely to require a visit to a physician, be hospitalized, or die than somebody of similar age without such conditions. In this sense, "high risk" does not refer to risk of contracting H1N1 influenza. As best is known, those with high-risk conditions are no more or less likely to contract a case of influenza than those without such conditions. The term "high risk" therefore relates to what happens after a person becomes clinically ill from influenza.

Can FluAid Special Edition be used to accurately estimate the number of cases, hospitalizations, and deaths in the U.S. in fall/winter 2009–10 due to the novel H1N1 flu virus?

Numbers derived from FluAid Special Edition are estimates of the probable number of cases, hospitalizations, outpatient visits, and deaths prior to an intervention for a given scenario, so accuracy cannot be guaranteed. As such the estimates provided by FluAid Special Edition are illustrations of the potential impact and are suitable for planning and preparing a response to 2009 H1N1.

Why is a range of numbers sometimes used to express the potential impact of the novel H1N1 flu virus during 2009–10 influenza season in the U.S.?

Ranges indicate the uncertainty of any outbreak. The outcome—the number of cases, hospitalizations, outpatient visits, and deaths—of the 2009 H1N1 flu pandemic during the 2009–10 influenza season cannot be known in advance; however, data collected from the impact of 2009 H1N1 in the Spring of 2009 is used in FluAid Special Edition to determine the estimated number of cases and a probable range (i.e., minimum, maximum, and most-likely number) of resulting health outcomes. These numbers can be adjusted to reflect estimates for a mild, moderate, or severe outbreak, ranging, for example, from an attack rate of 7.5% to 20%.

During the Spring 2009 H1N1 flu outbreak in the U.S., data on the actual number of cases, hospitalizations, outpatient visits, and deaths was collected and evaluated. This data is relevant because it relates to the impact of H1N1 in humans and can be used as the basis for predicting future outcomes, using various gross attack rates. It is this data that is used as the basis for FluAid Special Edition. Provided the H1N1 virus does not change markedly, this program should result in illustrations of the probable number of cases, hospitalizations, outpatient visits, and deaths resulting from a low, moderate, or severe attack rate in 2009–10 influenza season.

Can FluAid Special Edition be used as a planning tool by non-governmental agencies, such as businesses and hospitals?

Yes, FluAid Special Edition can be used by non-governmental organizations to estimate how they might be impacted by the 2009 H1N1 flu pandemic.

Can FluAid Special Edition be used to estimate the impact of the 2009 H1N1 flu virus in long-term care and pediatric care facilities?

Yes, FluAid Special Edition can be used to some degree to illustrate the probable impact of 2009 pandemic influenza A (H1N1) in such facilities. However, in FluAid Special Edition, health outcome rates are averaged over age groups; that is, estimates for the probable impact among children are averaged for all children 0–17 years old, and estimates for adults are averaged for people 18–64 years of age and for those 65+ years of age. If these age groupings do not fit your situation, you may need to alter the rates of health outcomes. The age groups can be altered to some small degree (e.g., 0–14 years instead of 0–18 years). This may be done by accurately tracking how you are grouping your population data (i.e., what are your specific age groups?).

Can FluAid Special Edition be used to illustrate how or when people will become ill or how the 2009 H1N1 flu pandemic might spread over time?

No, the software model is not an epidemiologic model and, thus, cannot describe how or when people will become ill or how the pandemic might spread through a geographic region over time.