Why don’t migratory birds get flu?

  At the turn of autumn and winter every year, many birds in Europe and Asia will start to fly to the warm south and enjoy the sun in tropical Africa. When spring comes, they will return to the warming Paleobe (a division in zoogeography that includes Europe, northern Asia, and northern Africa), where they mate and raise their offspring. Researchers want to know why these long-distance flying birds will not be infected with the virus during the journey and contract diseases such as flu.
  ”When we go abroad for a holiday, we need to be vaccinated,” said Emily O’Connor, an ecologist at Lund University in Sweden. “But there is no way for birds to get drug protection. So we are confused, why we have difficulty coping with it. Can they handle things?”
  In order to find the answer, O’Connor and his colleagues classified more than 1,300 songbirds into migratory birds, African resident birds, and Paleobeian resident birds. For example, Meadow Pipit is a species that lives in the Gubei region. Resident bird. Then, the researchers captured 32 representative bird species and collected their blood samples for genetic analysis to find genes that encode MHC-I protein (a type of immune protein involved in identifying pathogens). O’Connor said that the greater the diversity of these genes, the more types of viruses that the animal immune system can detect.
  The test results show that the immune system of African resident birds is the strongest. Since most Palearctic birds originally originated in tropical regions and then spread northward, researchers speculated that the genetic diversity of MHC-I may be low in these Palearctic birds.
  ”Because of the need to travel between the two places, migratory birds have to deal with two different pathogens,” O’Connor said. “I originally expected their genetic diversity to be the highest among the three types of birds, so when it was discovered that their genetic diversity was comparable to that in Europe, I’m really surprised when the resident birds are very similar.”
  Young birds are most susceptible to pathogen infection when they just hatch. At the same time, the pressure of reproduction makes their parents more likely to get sick at this time. For these two reasons, O’Connor speculates that evolution will be biased towards selecting genes that help migratory birds fight against common pathogens in the north (that is, where they are born), at the cost of sacrificing genes that protect against tropical pathogens.
  Maybe. Migratory birds also have other forms of non-pathogen-specific (that is, independent of MHC-I protein) immunity. Camille Bono, an evolutionary biologist at the University of Exeter, UK, said: “We need to further explore whether migratory birds are better Use less specific immunity and more non-specific immunity.”