Of the 73 pediatric patients who died of influenza-related causes in the United States during the 2006–2007 flu season, 35% had bacterial coinfection—a fivefold increase over the 2004–2005 season.
Most often, that bacteria was methicillin-resistant Staphylococcus aureus (MRSA).
“Physicians should consider treating children with suspected S. aureus pneumonia during influenza season with vancomycin or other antibiotics to treat MRSA when [the children] reside in areas where MRSA is prevalent” or when they have additional MRSA risk factors, including underlying conditions or a history of infection, wrote Lyn Finelli, of the National Center for Immunization and Respiratory Diseases, Atlanta, and colleagues (Pediatrics 2008;122;805–11).
Dr. Henry Bernstein, a pediatrician in Lebanon, N.H., and a member of the American Academy of Pediatrics' committee on infectious diseases, agreed.
“It's something that we as practicing pediatricians need to be aware of: When somebody gets the flu, we must evaluate whether in fact it's a typical, routine case of the flu or it's something more, if it's not following the course that we expect.”
But the most important lesson from this analysis is to get children vaccinated, Dr. Bernstein said in an interview. “Half of those [deaths] are in kids who could have gotten the flu vaccine, and potentially it could have been prevented. So that's tragic. These aren't just kids who have chronic health conditions. Many of these kids were healthy children. That's a shame,” said Dr. Bernstein, who was not involved in the study.
The researchers defined an influenza season as lasting from Oct. 1 to Sept. 30 of the following year, such that the 2006–2007 season lasted from Oct. 1, 2006, to Sept. 30, 2007. They also defined a child as being fully vaccinated when he or she had received the appropriate number of doses at least 14 days before illness onset.
In the first season looked at, 2004–2005, the rate of bacterial coinfection in the 47 pediatric influenza-related deaths was 6%. By the next season, it was 15%, and by 2006–2007, the rate was 35%. “Overall, S. aureus was isolated from a sterile site or endotracheal tube culture in 1 child in 2004–2005, 3 children in 2005–2006, and 22 children in 2006–2007,” wrote the authors. Of these 26 infections, 15 were MRSA, 6 were methicillin-susceptible S. aureus (MSSA) and 5 were S. aureus of unknown susceptibility.
The authors hypothesized that influenza might increase patient vulnerability to bacteria by damaging the epithelial layer of the tracheobronchial tree, “enhancing staphylococcal adherence,” or possibly suppressing the “respiratory burst response” and phagocytic activities that occur in a healthy immune system.
Regardless of the mechanism, they conceded that there is likely underreporting of bacterial coinfection in fatal influenza cases in the United States. Indeed, according to the authors, flu-related deaths may themselves be underreported: “Despite the availability … of influenza tests, influenza testing is not currently routinely incorporated into the diagnostic work-up of most children who are seen in primary care of emergency department settings with influenza-like illness.”
In all, 166 children in the United States died of influenza-related causes between Oct. 1, 2004, and Sept. 30, 2007. The ages of affected children ranged from 0 to 17 years. The median ages in the three cohorts ranged from 3 to 7 years.
Currently, all children aged 6 months to 18 years should be vaccinated, according to recommendations by the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices. Only 5% of those patients for whom vaccination was recommended had received the vaccine.
“Influenza is a serious disease,” said Dr. Bernstein. However, “There's no question that influenza is [also] vaccine preventable. You can't die from the flu if you don't get the flu.” And as the potential for coinfection with antibiotic-resistant bacteria increases from year to year, the need for vaccination is even more pressing, he said. And not just among patients.
“Health care personnel vaccination rates are somewhere around 50%, at most,” he said. “There's certainly room for improvement. Getting a flu vaccine every year ought to become a routine.”
The authors disclosed no conflicts of interest.