The number of swine influenza cases as well as the diversity of circulating flu viruses have increased in the past several years, based on experience at Iowa State’s Veterinary Diagnostic Laboratory, Phillip Gauger, DVM, associate professor at the university, told Pig Health Today.Swine influenza is an RNA virus, which makes it prone to constant change in one of two ways. The virus either undergoes antigenic drift — natural mutations — or antigenic shift, which occurs when segments from two different viruses come together to form a new genome, Gauger explained.Both processes contribute significantly to the antigenic diversity seen in the field and make swine flu harder to control. Each of the two major subtypes of swine flu — H1 and H3 — have different genetic “clades” or groups. It’s important to know which clade is circulating on a farm so the best decisions can be made regarding vaccination, he said, noting that more veterinarians are obtaining genetic sequencing of flu viruses.

　　兽医学博士、大学副教授Phillip Gauger告诉《今日猪健康》，根据美国爱荷华州兽医诊断实验室的经验，在过去的几年中，猪流感病例的数目在不断增长，而当下正在传播的流感病毒的多样性也在不断增加。Gauger博士解释说：“猪流感是一种核糖核酸(RNA)病毒，很容易通过两种突变方式进行不断变化。病毒要么进行抗原漂移-自然突变，要么就是通过抗原性非连续变异。后者产生的原因是，来自两种不同病毒的基因片段整合到一起，形成了一种新基因，此时就会发生抗原性非连续变异。”这两种过程都会对感染现场看到的抗原多样性产生重大影响，让猪流感更难被控制。猪流感的两种主要子类型分H1型与H3型，每一种都有不同的基因演化或基因组，对于感染猪流感的农场，只有了解是哪一种基因演变过程，才能做出最佳的决定，研制相关的疫苗。越来越多的兽医都在试图获取流感病毒的基因序列。