Each year, the influenza virus seems to be advancing. And every year, public health officials try to predict what the novel strain will be and how it will affect the population in order to best combat it.
A latest study may make the health officials task a little easier. The study is believed to break ground by working across scales and linking sub-molecular changes in the influenza virus to the possibility of influenza outbreaks. More so, this study appears to show the relationship between the evolution of the virus and immunization rates needed in order to prevent an epidemic in the population.
The study revealed that by means of earlier vaccinations or infections with earlier strains of the influenza virus, many individuals already seem to have some level of immunity. However, the influenza virus apparently is constantly evolving. By substituting different amino acids at key molecular points, the virus may increase its probability of evading the immune system’s defenses thereby allowing it to reproduce and spread.
“Public health officials will be able to assess the usefulness of a vaccine based upon its relationship to the current influenza strain and the population’s immunity level,†says lead author of the study, and an assistant professor Andrew W. Park, who holds a joint appointment in the University of Georgia Odum School of Ecology and in the College of Veterinary Medicine.
Park was of the opinion that as the number of amino acid differences between a novel strain and the strain an individual was vaccinated against increases, the chances of becoming infected appears to rise as does the possibility of becoming infectious and the length of time they will remain infectious.
Supposedly, these factors combine to increase the likelihood of an outbreak in a population. Working with equine influenza, the team of experts examined the chances of an influenza outbreak in a population that had all been vaccinated with the same strain of the virus.
The findings of the study revealed that outbreaks seem to have begun taking place when there were two or more amino acid differences. Furthermore, the size of the outbreak appears to have increased with the number of amino acid differences.
The findings also revealed that large outbreaks seem to be more likely to occur if the virus and the vaccine were from different antigenic clusters which signify that a host’s immune system perceives the two strains as different. Comparing these results with a previous human influenza study was believed to have discovered similar trends.
However, an added key factor in determining the risk of an outbreak in real populations may be the individual variation of immunity in the population. Since the virus keeps changing, so do the vaccines used against it.
This seems to cause the immunity of the population to be heterogeneous wherein some individuals have been infected with or vaccinated against previous year’s influenza strain, some against strains from earlier years, and some have no immunity at all. Park along with his colleagues found that the degree of variability of immunity in the population appears to play a crucial role in determining the possibility of an outbreak.
He added that in measuring for the foremost time how the difference between the population’s immunity status and a latest virus strain influences the risk of an epidemic, the team seems to have taken a critical step towards linking these relationships with the dynamics of epidemics.
Also, it may not only be for influenza but also for a wide range of infectious diseases. He claimed that these findings could possibly assist in informing efforts to prevent future outbreaks.
The findings of the study have been published in the journal, Science.