Quote from Effect Measure - A blog by US Public Health Officials:
Pediatric complications and deaths with swine flu
Category: Swine flu
Posted on: July 24, 2009 7:54 AM, by revere
Yesterday CDC's Morbidity and Mortality Weekly Report (MMWR) carried an a note about neurologic complications in children with swine flu. Central nervous system effects -- seizures, encephalitis, encephalopathy, Reye syndrome, and other neurologic disorders -- are known to occur with seasonal influenza in children, but whether they are more or less common with the swine flu variant is unknown at the moment. The MMWR reports four cases from Dallas County, more as a reminder that these kinds of complications can occur and should be considered whenever a child with influenza-like illness (ILI) presents with unexplained seizure or mental status changes. It's also a reminder of something else. That influenza, whether seasonal or pandemic varieties, presents different clinical pictures in different age groups, but pandemic flu shifts the age distribution of ill cases towards the younger age groups. The difference is not necessarily a clinical difference but an epidemiological one. First, the clinical picture:
This is the first report describing patients with neurologic complications associated with novel influenza A (H1N1) virus infection. The severity of the neurologic disease in the four patients described in this report was less than the typical disease described in two studies of neurologic complications associated with seasonal influenza (1--2), which included reports of severe static encephalopathy and death. Only two of the four patients described in this report had seizures, and none died or had neurologic sequelae at discharge. Considering that clusters of influenza-associated encephalopathy in children have been reported during previous community outbreaks of seasonal influenza and that children appear to be infected with novel influenza A (H1N1) virus more frequently than adults, additional neurologic complications in children are likely to be reported as the pandemic continues. Clinicians should consider influenza associated encephalopathy in the differential diagnosis of children with ILI and seizures or mental status changes, and remain aware of the potential for severe neurologic sequelae associated with seasonal or novel influenza A (H1N1) virus infection. (MMWR, CDC [cites omitted])
If that sounds vague reassuring, it is important to remember that influenza infection is always potentially dangerous. Seasonal flu kills mainly those over 65, but pandemic flu targets the young, and while most "just have a case of flu" (in itself potentially nasty as the cases reported above show), every year children die and this year's flu season was no exception. For several years CDC has been trying to keep track of pediatric flu mortality and the striking thing about this year is the appearance of pediatric swine flu as a distinct second season. Here is a chart from last week's CDC surveillance report where it is easy to see that this year's pediatric mortality from seasonal flu looks very much like the three previous years (although last year was a very bad flu year), but that in addition pediatric deaths are occurring this year during weeks when there are no, or almost no, pediatric deaths in the previous seasons. This is another key marker of an influenza pandemic:
IPD27.jpg
Source: CDC, Influenza-associated pediatric mortality
Of the 90 pediatric deaths this year (there were 88 last year), 23 are from swine flu. Not all of the children had specimens collected, but of the 40 that did (all deaths, not just swine flu), about a third (15) had bacterial co-infections that contributed to their deaths, and Staph aureus was the organism in 9 of them (60%). Of these 9, 5 were MRSA, i.e., antibiotic resistant (see our post of the other day). This year, as in past years, the children with bacterial co-infections have been the older ones, most over 5 and two-thrids over 12 years old. Of the 9 swine flu fatal cases in children where specimens from normally sterile sites were obtained to see if there was bacterial co-infection, only one had a positive bacterial culture. It is still too early to say if this difference is a real difference in the likelihood of bacterial co-infection because no specimens were obtained from the majority (14 of 23) of the fatal swine flu cases.
The swine flu pandemic continues to be described in some quarters as "mild." In our view, "mild" is not a word that should be used in connection with influenza outbreaks, whether seasonal or pandemic.