Social networks influence how H1N1 influenza outbreaks spread across
schools, communities and households, researchers have found.
Using data collected during an H1N1 pandemic influenza outbreak at a
semirural Pennsylvania elementary school, researchers studied 370 students (81%
of the school’s enrollment) from 295 households. Data collected included
seating charts, bus and bell schedules, nurse logs, attendance records and
questionnaires regarding social network factors such as who the students’
playmates were. The information was interpreted using the Markov chain Monte
Carlo sampling and data augmentation techniques to create probability models
for how the virus spread.
In accordance with observed assortative mixing among boys and girls,
researchers found that boys were three times more likely to transmit influenza
to other boys than to girls; the same was true for the girl-to-girl
transmission. The rate of transmission between classmates was five times higher
than between children in the same grade but in different classrooms and 25
times higher than between students not in the same grade; however, sitting next
to an infected student in class did not significantly raise a student’s
risk of infection.
For more information:
- Cauchemez S. Proc Natl Acad Sci.
2011;doi:10.1073/pnas.1008895108.
Theodore C. Eickhoff
This is an interesting study, with results that should probably surprise
no one. Nonetheless, it’s nice to finally see some data on what has been
widely assumed to be the case. Nothing has been said about how influenza was
diagnosed; nonetheless, if the study was carried out during the pandemic in the
fall of 2009, and absenteeism in the school was so great that the school was
closed, it’s a safe bet that a substantial majority of the respiratory
illnesses were indeed pandemic H1N1 influenza.
Note that these were elementary school children, and hormones had not
yet started to flow in most of them. It would be interesting to see how these
transmission patterns changed as children got older and entered the
post-pubertal years.
It’s perhaps a bit surprising that sitting next to an infected
student did not apparently increase the risk of risk of infection. Some
assessment of “respiratory hygiene” among these children would have
been helpful in understanding and interpreting the results.
–Theodore C. Eickhoff
Infectious Disease News Editorial Board
member
Disclosure: Dr. Eickhoff reports no relevant financial
disclosures.