Child flu deaths may be linked to CA-MRSA

Fujian strain eludes vaccine to some degree

While the cases remain under investigation, the deaths of some children due to influenza this year may be linked to underlying infections with community-acquired methicillin-resistant staphylococcus aureus (CA-MRSA), the director of the Centers for Disease Control and Prevention (CDC) conceded.

"Staphylococcal organisms, in general, are often seen in association with influenza," Julie Gerberding, MD, said at a recent press conference. "And when a Methicillin-resistant or a drug-resistant staph infection is common in the patient population or common in the community, it’s not surprising that that would be the kind of staph that would complicate influenza."

Emerging in independent strains from its nosocomial cousins, CA-MRSA has been linked to an increasing number of community infections over the last few years. A coinfection with the bug could complicate and worsen the course of influenza, but nothing has been confirmed at the CDC.

"There are some reports," she said. "I don’t have documentation of that. I’m not aware that we have the organisms here at CDC. But it would not be at all surprising to see a drug-resistant staph infection complicate either a child or an adult with influenza. So not a surprise, but something that just adds an additional complexity to the treatment."

A common cause of more severe illness and death is bacterial infection that can complicate the viral influenza illness. "Some of the children who have died have had complicating bacterial infections," Gerberding said. As of early December, six children (ranging from 21 months to 15 years old) had died of influenza in Colorado. Other reports have come in as well.

"There are reports of children with serious influenza and deaths among children from influenza," Gerberding said.

"And that is something that is very sad and also something that we’re evaluating very carefully to determine whether or not there’s anything about this particular flu strain that’s preferentially affecting children or causing more severe disease in children. We don’t know the answer to the question yet. It is common for children to develop severe influenza and for deaths to occur in every flu season, unfortunately, so it will take us some time to figure that out," she added.

A Fujian fly in the ointment

There are signs that a particularly vicious flu season could be afoot, given its early start and the presence of a circulating virus not specifically covered by the vaccine — H3N2, the so-called Fujian strain.

"Part of the reason why this year’s vaccine does not contain the Fujian strain [is] because it came up late in the season, we had trouble growing it in eggs, and so it couldn’t be produced in time to make it into the vaccine that we’re distributing right now," Gerberding said. "Viruses are finicky. They don’t always grow well in eggs. For example, some avian influenza viruses — which, you know, are lethal in chickens — have a terrible time growing in chicken eggs because they kill the cells that they’re trying to grow in. So this is just a complication of this particular vaccine methodology."

The Fujian strain eventually was grown for vaccine use, but national and international health officials feared the whole vaccine program would be delayed if they tried to add the strain to the current vaccine. "They made the decision that it would not be prudent to try to race to get the Fujian strain in this year because it could jeopardize the whole vaccine production and we would end up starting the year with no vaccine at all, she said.

Fortunately, the vaccine does contain the H3N2 Panama strain, a very close match to the Fujian strain. "Our experience so far has been that the vaccine will still offer protection, although we won’t know for several weeks or months exactly how close that cross-protection is," she said. "We are initiating some studies to make sure that we’ll have an answer to that question as we go forward."

With vaccine supplies running short, the government is seeking additional vaccine from other countries, she said. In the interim, the highest priority for vaccination is for people who are at highest risk of influenza complications. "Let me stress that those are people older than 65 years old who have the highest risk, as well as people with chronic medical conditions, and children between the ages of 6 months and 23 months," Gerberding said.

While few doses of the standard killed virus remain, there are some 4 million doses left of the new live attenuated nasal vaccine FluMist. "Unfortunately, it’s not licensed for children under 5 or for people older than 49 years of age this year, although possibly that would happen sometime in the future," she said. "We are still encouraging people to be immunized and to be persistent about locating vaccine. We are recommending that the priority be given to people at the highest risk for complications."