Neurologic Conditions Raise Flu Mortality Risk in Children

Nancy A. Melville

August 29, 2012

August 29, 2012 — Nearly two thirds of children who died from underlying conditions associated with the H1N1 influenza outbreak in 2009 had neurologic disorders, according to results of a study conducted by scientists with the Centers for Disease Control and Prevention (CDC).

The new report is published online August 29 in the journal Pediatrics.

The H1N1 virus took a high toll on children in general — the number of flu-related deaths among children younger than 18 years of age during the pandemic was as much as 5 times higher than the median number of pediatric deaths reported in the 5 previous flu seasons, the researchers noted.

Underlying conditions were present in 68% of children who died, and among 336 children for whom medical information on underlying conditions was available, 227 had one or more conditions that increased the risk for influenza complications.

Neurologic conditions were disproportionately high, representing the most common disorders. These conditions were reported in 146 (64%) patients with underlying conditions, and neurodevelopmental disorders and epilepsy were substantially more common than neuromuscular disorders.

A "Somber Reminder"

Among those with neurologic conditions, as many as 75% had other conditions that increased their risk for influenza complications, such as pulmonary disorder, metabolic disorder, or heart disease.

"We've known for some time that certain neurologic conditions can put children at high risk for serious complications from influenza," said Lyn Finelli, MD, chief of the surveillance and outbreak response team in CDC's Influenza Division, in a press statement.

"However, the high percentage of pediatric deaths associated with neurologic disorders that occurred during the 2009 H1N1 pandemic was a somber reminder of the harm that flu can cause to children with neurologic and neurodevelopmental disorders."

Influenza-associated pneumonia and acute respiratory distress syndrome (ARDS) represented the most common complications among children with neurologic disorders, and pulmonary disorders were common in the group.

"The finding that most children with neurologic disorders developed pneumonia or ARDS as an acute complication of influenza is not unexpected, given that these children might have difficulty with muscle function that compromises clearing of pulmonary secretions," the authors write.

Children with neurologic disorders generally were older (P = .02) and had a longer duration of illness (P < .01) compared with children without underlying medical conditions.

Among children with neurologic disorders for whom information on vaccination status was available, only 21 (23%) had received the seasonal influenza vaccine and 2 (3%) were fully vaccinated for 2009 H1N1.

Risk of Not Vaccinating

Several factors may explain the low vaccination numbers, including the fact that vaccination records were not available for some patients, and that the vaccine was not even available until after the flu had spread, co-author Georgina Peacock, MD, told Medscape Medical News.

"Some of the deaths may have occurred even before the vaccine became available, but regardless, I think this shows we still have work to do," said Dr. Peacock, a medical officer and developmental-behavioral pediatrician with the Prevention Research Branch of the CDC's National Center on Birth Defects and Developmental Disabilities, in Atlanta, Georgia.

We need to get the message out that these children need to be vaccinated because they are at a higher risk.

"We need to get the message out that these children need to be vaccinated because they are at a higher risk."

Parents of children with neurologic disorders may have heightened vaccination safety concerns, but the greater risks of not vaccinating should be emphasized, Dr. Peacock added.

"We do hear a lot of concerns among parents regarding vaccine safety, but it's important that they also know the risk [of not vaccinating], particularly for children with neurologic conditions. Vaccination is a first-line protection for these children."

The authors warned clinicians to be wary of the potential for false-negative results on rapid influenza diagnostic tests (RIDTs) when flu symptoms are apparent.

They noted that as many as 10% of respiratory specimens collected from pediatric H1N1 deaths had initially been negative for influenza on RIDT, but were later confirmed as positive with reverse transcription polymerase chain reaction (RT-PCR).

"A false-negative RIDT can result in a child having a delay in treatment, so the important message is if a doctor thinks a child has influenza, particularly one with a neurologic condition, they should begin antiviral treatment right away, regardless of the result of the rapid test," Dr. Peacock said.

The authors have disclosed no relevant financial relationships.

Pediatrics. 2012;130:390-396. Published online August 29, 2012. Abstract

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