Vaccination of influenza a virus decreases transmission rates in pigs

Romagosa, Anna; Allerson, Matt; Gramer, Marie; Joo, Han Soo; Deen, John; Detmer, Susan; Torremorell, Montserrat

From the deterministic models, R 0 estimates for the NV replicates ranged from 8.51 to 19.81. Therefore, following the introduction of one typical infected pig into a completely susceptible population, 9 to 20 secondary cases can be expected due to the typical infectious pig during its entire infectious period. The NV stochastic models reiterate this estimate by showing that major influenza virus outbreaks are likely to occur in small naïve populations following the introduction of one infected pig. The distribution of new cases was also similar across replicates for the NV group with either small or large outbreaks occurring. Once the initial infected pig transmitted the infection to a susceptible pig, the infection chain proceeded until all or nearly all animals were infected. These simulations likely describe high morbidity rates observed in field settings with susceptible animals. The NV stochastic models also clearly show that no new cases or minor outbreaks can also occur, albeit at low frequency, in a similar population even if R 0 values are high.