by revere, cross-posted at Effect Measure

Every parent’s or grandparent’s nightmare is to have their darling little one suddenly carried off by illness. Flu isn’t on the radar screen of most parents but in recent years the public health community is taking notice. The first alarm occurred in the bad flu season of 2003 – 2004 when a retrospective tally showed over 150 pediatric deaths associated with flu. That was more than half again as much as we thought were occurring, although data was not very good. So a new pediatric surveillance system was put in place. One of the things it is showing is that methicillin resistant Staphylococcus aureaus (MRSA) is a surprisingly common accomplice in pediatric flu deaths. An excellent summary by Maryn McKenna at CIDRAP News gives some of the details. McKenna is an authority on MRSA and knows a lot about flu, so her piece is well worth reading, as is her blog, Superbug, which focuses on MRSA.

This is from her CIDRAP piece:

The number of children who have died from a combination of influenza infection and bacterial pneumonia–in many cases due to the superbug methicillin-resistant Staphylococcus aureus (MRSA)–has risen sharply over the past few years, federal epidemiologists say in a new report that urges flu shots as a preventative.[snip]

Staph pneumonia is not a new phenomenon; from 3% to 10% of pneumonias that begin outside hospitals have been attributed to staph, but those pneumonias tend to occur in the elderly and immune-impaired. And the severity of simultaneous staph and flu infections has been documented after each influenza pandemic, in which large numbers of deaths were attributed to bacterial pneumonia.

But the staph pneumonias recorded by the new reporting system represent an apparently new development, because they occurred in previously healthy children infected with a seasonal flu virus that presumably does less damage to the lungs and immune response than a novel pandemic one. And they appear to be occurring at the same time as a rapid rise in MRSA colonization in the United States, which doubled between 2001 and 2004. (Maryn McKenna, CIDRAP News)

 In the past secondary bacterial infections in flu were thought to be mainly Streptococcus pneumoniae (“Diploccus” or pneumococcus) or Haemophilus influenzae. As McKenna notes, Staph pneumonia was for the old, the immunocompromised and the chronically ill. But infection with influenza virus seems to have special abilities. A recent paper in Nature Medicine [Sun K, Metzger DW. Inhibition of pulmonary antibacterial defense by interferon during recovery from influenza infection. Nat Med 2008;14:558-64] suggests that the ability to clear bacterial invaders is inhibited early on during infection with influenza virus. The flu virus may be turning healthy children into immuno-compromised children (at least locally in the lung), accounting for the increasing MRSA super-infections, whose rate has been increasing year on year:

Bacterial infection superimposed on flu was not the only cause of death; children also died from seizures, encephalitis, and shock. But it played an important role: Coinfections were involved in 6%, 15%, and 34% in the three successive seasons, a fivefold increase. Almost all of that increase was due to S aureus: There were one staph infection in 2004-05, 3 in 2005-06, and 22 in 2006-07, and 64% of the staph infections were drug-resistant.

The relative absence of pneumococcal pneumonia may be related to availability of a vaccine against this bacterial agent. There is no vaccine for MRSA. But there is an influenza vaccine, and children 6 months and older have been added to the list of those for whom flu vaccination is recommended. At my recommendation my daughter had our grandchild vaccinated. I think it’s a good idea, maybe even a life saving one. The newest grandchild is too young to be vaccinated for this flu season. So I’ll have to use my usual coping mechanism for a grandpa’s chronic anxiety: worry.