Transmissibility of swine flu at Fort Dix, 1976

Abstract

The 1976 outbreak of A/New Jersey/76 influenza in Fort Dix is a rare example of an influenza virus with documented human to human transmission that failed to spread widely. Despite extensive epidemiological investigation, no attempt has been made to quantify the transmissibility of this virus. The World Health Organization and the United States Government view containment of emerging influenza strains as central to combating pandemic influenza. Computational models predict that it may be possible to contain an emergent pandemic influenza if virus transmissibility is low. The A/New Jersey/76 outbreak at the United States Army Training Center at Fort Dix, New Jersey in January 1976 caused 13 hospitalizations, 1 death and an estimated 230 cases. To characterize viral transmission in this epidemic, we estimated the basic reproductive number and serial interval using deterministic epidemic models and stochastic simulations. We estimated the basic reproductive number for this outbreak to be 1.2 (supported interval 1.1-1.4), the serial interval to be 1.9 days (supported interval 1.6-3.8 days), and that the virus had at least six serial human to human transmissions. This places the transmissibility of A/New Jersey/76 virus at the lower end of circulating flu strains, well below the threshold for control.

Does homologous reinfection drive multiple-wave influenza outbreaks? Accounting for immunodynamics in epidemiological models

“…6 (upper panels) shows the expected fraction of individuals infected at least once by a mutant during the first post-pandemic season ( F I . post-pdm) as a function of the immune escape σ and the relative increase in transmissibility Δ R 0 / R 0 , for five different values of R 0 in agreement with pandemic scenarios in large populations (Lessler et al, 2007). As R 0 increases the pandemic becomes more and more severe so that the expected fraction of protected individuals at the beginning of the post-pandemic season ($\overline{H}$) increases.…”

“…Indeed, R 0 has been estimated around 2 (Lessler et al, 2007) which is below the HR threshold $R_0^{*}$. In these cases, HR would have only increased the force of infection, and thus the number of infected hosts, by a few percent.…”

Pathogenesis of Pandemic Influenza A (H1N1) and Triple-Reassortant Swine Influenza A (H1) Viruses in Mice

“…Prior to 2009, the largest cluster of H1N1 swine influenza cases occurred during an outbreak in 1976 which resulted in the infection of up to 230 soldiers at Fort Dix, NJ, with 13 severe cases and one fatality (12). The outbreak was limited to Fort Dix, possibly due to the poor transmissibility of this virus (21). Triple-reassortant swine H1N1 influenza viruses (containing avian, human, and swine genes) have additionally been associated with human infection since 2005 (11,37).…”

Pandemic Influenza Vaccines

“…In 1946 an H1N1 virus that was first seen in Japan and Korea spread to military bases in the USA (Lessler et al 2007). Further spread was not observed.…”