Protecting residential care facilities from pandemic influenza

Abstract

It is widely believed that protecting health care facilities against outbreaks of pandemic influenza requires pharmaceutical resources such as antivirals and vaccines. However, early in a pandemic, vaccines will not likely be available and antivirals will probably be of limited supply. The containment of pandemic influenza within acute-care hospitals anywhere is problematic because of open connections with communities. However, other health care institutions, especially those providing care for the disabled, can potentially control community access. We modeled a residential care facility by using a stochastic compartmental model to address the question of whether conditions exist under which nonpharmaceutical interventions (NPIs) alone might prevent the introduction of a pandemic virus. The model projected that with currently recommended staff-visitor interactions and social distancing practices, virus introductions are inevitable in all pandemics, accompanied by rapid internal propagation. The model identified staff reentry as the critical pathway of contagion, and provided estimates of the reduction in risk required to minimize the probability of a virus introduction. By using information on latency for historical and candidate pandemic viruses, we developed NPIs that simulated notions of protective isolation for staff away from the facility that reduced the probability of bringing the pandemic infection back to the facility to levels providing protection over a large range of projected pandemic severities. The proposed form of protective isolation was evaluated for social plausibility by collaborators who operate residential facilities. It appears unavoidable that NPI combinations effective against pandemics more severe than mild imply social disruption that increases with severity.nonpharmaceutical interventions ͉ SEIR stochastic model ͉ self-isolation periods ͉ social distancing ͉ visitor and staff restrictions

Global asymptotic properties of an SEIRS model with multiple infectious stages

“…The average incubation period of influenza is 1.9 days, so that 1 σ E = 1.9 days [5,6,14,[28][29][30]. Similarly, the average infectious period is 5 days [29,30].…”

“…Since the determinant of G is non-zero, it follows that system (26), which has the form of a system given in (30), can only have a unique solution Z =0 (which corresponds to the DFE, E 0 ).…”

“…Similarly, the average infectious period is 5 days [29,30]. Since the numerical simulations in this study are based on the model (2) with 3 infectious stages (i.e., m = 3), the infectious period ( 1 3) is distributed such that the sum 1 σ 1 + 1 σ 2 + 1 σ 3 equals the mean duration of 5 days.…”

“…2). The average mortality rates (δ i ; i = 1, 2, 3) range between 0.0062 to 0.035 per day [30]. Since the average mortality rate of any typical disease is expected to decrease with decreasing infectiousness [6], we choose δ 1 = 0.035, δ 2 = 0.015 and δ 3 = 0.0062 per day.…”

Pandemic Influenza Plans in Residential Care Facilities

“…8,9 RCFs are highly susceptible to virus outbreaks and rapid propagation in a pandemic. 10 Unlike nursing homes, RCFs are not federally regulated and infection prevention and control standards vary widely based on individual state regulations. 11 If community or state-level pandemic planning exists, RCFs are rarely included in these planning efforts.…”