Sick switch can increase infections
Research suggests sending sick staff home could make things worse.
Policies that focus on replacing infected individuals with healthy ones, such as for teachers, may actually spread the disease more rapidly through a community during an epidemic, according to a paper by US and Spanish scientists.
The researchers show that replacing a sick person with a healthy one puts the healthy person at higher risk of getting the disease themselves, which can cause a disease to spread faster than predicted.
The standard practice follows clear logic: infected workers are incapacitated, and run the risk of infecting others.
However, standard models for understanding the dynamics of a spreading disease fail to incorporate the fact that these healthy substitutes are being introduced into a more dangerous situation than they were in previously.
By specifically factoring-in this increased risk, the researchers found that this policy of replacement — known as ‘relational exchange’ — can cause a disease at its peak to transmit at a rate faster than would be expected at the onset of the outbreak.
The authors tested their model using data from real-world influenza and dengue outbreaks.
Both diseases are subject to seasonal effects, but dengue, unlike influenza, features a delay between transmission and behaviour, and is expected to be less susceptible to the impact of relational exchange.
The authors found that their model was consistent with data for 17 influenza outbreaks in the United States at a national level, 25 years of influenza data at a state level, and 19 years of dengue virus data from Puerto Rico.
The team hopes its findings can better inform public health decision-making during outbreaks.