The spread of awareness and its impact on epidemic outbreaks

Abstract

When a disease breaks out in a human population, changes in behavior in response to the outbreak can alter the progression of the infectious agent. In particular, people aware of a disease in their proximity can take measures to reduce their susceptibility. Even if no centralized information is provided about the presence of a disease, such awareness can arise through first-hand observation and word of mouth. To understand the effects this can have on the spread of a disease, we formulate and analyze a mathematical model for the spread of awareness in a host population, and then link this to an epidemiological model by having more informed hosts reduce their susceptibility. We find that, in a well-mixed population, this can result in a lower size of the outbreak, but does not affect the epidemic threshold. If, however, the behavioral response is treated as a local effect arising in the proximity of an outbreak, it can completely stop a disease from spreading, although only if the infection rate is below a threshold. We show that the impact of locally spreading awareness is amplified if the social network of potential infection events and the network over which individuals communicate overlap, especially so if the networks have a high level of clustering. These findings suggest that care needs to be taken both in the interpretation of disease parameters, as well as in the prediction of the fate of future outbreaks. mathematical model | rumor spread | behavioral response | social networks H uman reactions to the presence of disease abound, yet they have rarely been systematically investigated (1). Such reactions can range from avoiding social contact with infected individuals (social distancing) to wearing protective masks, vaccination, or more creative precautions. It has been shown, for instance, that local measles outbreaks are correlated with the demand for measles, mumps, and rubella vaccines (2). Similarly, the demand for condoms rises in areas where AIDS is prevalent (3), and condom use has been linked to the knowledge of someone who has died of AIDS (4).Behavior that is responsive to the presence of a disease can potentially reduce the size of an epidemic outbreak. On closer inspection, it is not so much the presence of the disease itself that will prompt humans to change their behavior, as awareness of the presence of the disease. A change in behavior can be prompted without witnessing the disease first hand, but by being informed about it through others. This information in itself will spread through the population and have its own dynamic. For example, according to the Chinese Southern Weekend newspaper, the text message "There is a fatal flu in Guangzhou" was sent 126 million times in Guangzhou alone during the 2003 severe acute respiratory syndrome (SARS) outbreak (5), causing people to stay home or wear face masks when going outside. This figure stands in stark contrast to the comparatively low number of 5,327 cases recorded in the whole of China (6). It is not clear how much the individual behaviora...

Endemic disease, awareness, and local behavioural response

“…A longer duration of immunity of aware recovered individuals, on the other hand, lowers the disease prevalence in the endemic equilibrium, however it does not change the invasion conditions. As we have shown previously, such effects on the invasion threshold can be observed in a well-mixed population only if awareness does not deteriorate as it spreads through the population [7].…”

“…While we did extended the methods devised by Keeling [11] for pair approximations on clustered networks to our more complex system, these failed to generate convincing results or capture any of the effects we previously showed to operate when disease and awareness interact on clustered networks [7]. In fact, we found that the sheer complexity of the system of equations resulting from the pair approximation we derived made it difficult to go beyond the simple observations presented here.…”

“…We recently presented a model for the spread of awareness in response to an epidemic outbreak and analysed the effect this can have on the outbreak [7]. Here, we expand on that idea to study a simplified model of the interaction between local behavioural response and endemic disease.…”

New Influenza A/H1N1 (“Swine Flu”): information needs of airport passengers and staff

“…It was hoped that this would enable and encourage travellers to protect themselves and to prevent the spread of infection by promoting the uptake of hygiene measures such as hand washing and tissue use. In the absence of specific prophylaxis, using communication to increase hygiene behaviours may be the most effective strategy to interrupt the chain of infection among members of the public 3 , 4 . At the same, providing airport passengers and staff with relevant information about the outbreak might also be expected to reduce levels of concern, 5 by reducing levels of uncertainty about the nature, prevention or treatment of swine flu 6 …”

Modelling behavioural contagion

“…Modelling techniques have so far typically involved either explicit stochastic simulation [3 -6], or else application of mathematical models originally developed for other applications, such as the Susceptible-Infectious-Susceptible (SIS) epidemic model considered by Kiss et al [7] and Funk et al [8]. An alternative is to use a discrete-time formalism [9,10], next-generation arguments [5] or methods from statistical physics [11,12] to obtain results about asymptotic behaviour of socially motivated models, although typically calculating transient features of system dynamics requires Monte Carlo simulation.…”