Encouraging people to stay home instead of going out, along with other “non-pharmaceutical interventions” such as handwashing and wearing facemasks, can limit the spread of influenza virus during an outbreak according to a new study published in the open access journal BMC Infectious Diseases.
The article by researchers at UC Davis, Arizona State University, Georgia State University and Yale University provides evidence that the novel A/H1N1 influenza outbreak that hit Mexico City in April 2009 could have been worse, but spread of the virus was reduced by people’s behavioral response of distancing themselves from each other.
In April 2009 the Mexican federal government closed public schools in Mexico City and ‘social distancing’ measures were put in place. The researchers used home television viewing in Central Mexico as an indicator of behavioral response during the 2009 A/H1N1 pandemic.
Television ratings data are consistently and widely available and “highly correlated with time spent in the home,” said UC Davis economist Michael Springborn, lead author of the study. These data provide a good indicator for the level of social interaction, because time spent watching television generally increases with time spent at home. And when people are home, they are limiting the number of contacts they make.
“We found that the behavioral response to the outbreak was initially strong but waned sooner than expected,” said Springborn. This dynamic is interpreted as a “rebound effect”. At the onset of a flu outbreak, the public responds strongly to the directed control policies. But over time, there was evidence that people began to spend less time in the confines of their homes. This happened even through the true risk had not fully waned.
“This suggests that efforts to utilize social distancing to mitigate disease spread may have a limited window of efficacy, i.e. before pent up-demand for activities outside the home takes precedence,” Springborn said.
There is historical evidence for this behavior. Observations from the 1918 influenza pandemic in Australia showed that when the perceived risk decreased the public reverted back to normal behavior.
Certain age groups and socio-economic groups responded more strongly than others. The researchers found that the increase in TV watching was more pronounced for children and wealthier groups. The authors speculate that those from poorer backgrounds may face greater difficulty in taking self-protective actions like social distancing, for example due to less flexibility with working hours. These differences between demographic groups could have public health policy implications for directing outbreak response assistance to those with lower financial means or increasing access to paid sick-leave for low-wage workers.
The findings also provide insight for selection of the duration and strength of major interventions (closing of businesses and cancelling public events) versus other forms of assistance, such as distributing masks.
The study drew on the combined disciplinary strengths of epidemiology and economics to create a new model that incorporates behavioral responses into existing models of disease spread.
Social distancing policies may be effective against pandemic influenza. However, people don’t need to wait. It is important to remember that other behaviors, such as washing hands and wearing facemasks, could contribute and should be routine in order to reduce transmission.
Adapted from a BioMed Central news release.