CDC releases plans for possible early-warning system for flu

Several million Americans suffer from flu each year. By no small coincidence, about half of those may be hospitalized because of their condition. What if we could predict someone’s likelihood of being hospitalized in advance and help them protect themselves or others against developing flu symptoms?

A new CDC report (PDF) lays out a broad preliminary plan for such a project — although it focuses mainly on a tool for identifying people who are already susceptible to severe influenza and need to be targeted with flu vaccines. The aim is to track the role of a single influenza virus in influenza outbreaks (currently, the link between infections and hospitalizations has not been completely cracked).

The question of how best to target those vulnerable individuals to flu vaccines is a particular interest to American health officials, who are in the process of sharpening vaccine targets based on its effectiveness against strains predicted to circulate in the winter of 2012-2013. With one-in-five Americans expected to be hospitalized because of a flu virus infection, better tools for predicting who might be susceptible to those strains could save lives and money.

“This report helps us begin to determine how new tools and techniques will enable us to predict, and hopefully prevent, influenza hospitalizations,” said Richard C. Besser, acting director of the CDC’s National Center for Immunization and Respiratory Diseases. “We expect these tools to be ready for use during the next influenza season.”

Most people who end up hospitalized for flu symptoms don’t actually fall into that exclusive group of being particularly vulnerable to flu; doctors want to know whether patients are suffering from the most common kinds of flu illnesses, such as the low-grade sinusitis, influenza-like illness, or pneumonia that can include the flu, pneumonia pneumonia, bronchitis and sinusitis that often accompanies the flu. (Dementia is one of the other top risk factors for hospitalization in patients treated for flu, although it doesn’t lead to more hospitalizations than other illnesses.) The CDC used health insurance claims data to assess the likelihood of hospitalization based on a wide variety of factors, including age, gender, race, education, ethnicity, smoking status, chronic conditions such as asthma and diabetes, the presence of a pneumococcal disease, heart disease and other chronic conditions, alcohol use, and other lifestyle factors that have not been part of any previous analyses. The analysis also considers factors that contribute to hospitalization — such as possible underlying health conditions and patient personal behavior — but does not necessarily account for those risks.

(Such factors also include the number of other people around the patient with the flu, their health, the length of time spent in the hospital and their ability to access treatment. Hospitals, for instance, are generally required to notify each other of a person they’ve admitted because of flu. In turn, this can help spread information about the patient’s illness.)

“In general, the more illness you have in your background, the greater your chance of being hospitalized,” lead author Dr. Kevin M. Shwed told CNN.

Each year, flu vaccines are difficult to make and provide limited protection against some flu strains. So improving forecasting methods about influenza outbreaks will be essential to helping government officials and medical providers better predict which flu viruses are likely to spread and which ones will be most dangerous.

Dr. Timothy C. Herendeen, chief medical officer of Truven Health Analytics, which provided the CDC data, said the largest audience may only be interested in the study’s results that may involve potentially “substantial impacts on patients’ lives.” But the progress of the CDC analysis “can have implications in predicting influenza-related hospitalizations and death that may have benefits for public health objectives over the long term,” he said.

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