It’s one thing to measure such behaviour, but can this new
information help predict the shape of epidemics? At the start of this
book, we saw that during the 2009 influenza pandemic, there were
two outbreak peaks in the United Kingdom: one in the spring and one
in the autumn. To understand what caused this pattern, we simply
need to look at schools. These bring children together in an intensely
social environment, creating a potential mixing pot of infection; during
the school holidays, children have around 40 per cent fewer daily
social contacts on average. As you can see from the graph above,
the gap between the two pandemic peaks in 2009 coincided with the
school holiday. This lengthy drop in social contacts was large enough
to explain the summer lull in the pandemic. However, school holidays
can’t fully explain the second wave of infection. Although the first
peak was probably due to changes in social behaviour, the second
peak was mostly down to herd immunity.[16] The rise and fall of
infections during school terms and holidays can influence other health
conditions too. In many countries, asthma cases peak at the start of a
school term. These outbreaks can also have a knock-on effect in the
wider community, exacerbating asthma in adults.[17]
Dynamics of the 2009 influenza pandemic in the UK