**3. Transmission of species**

#### **3.1 Genes' transport of wild birds to poultry by antigenic shift**

As above, many avian influenza reasssortant viruses have emerged during viral transmission from wild birds (donor spices) to poultry (recipient species). LPAI viruses from wild birds have been reasserted with other influenza virus strains of poultry and changed virulence in poultry. If LPAI viruses could not adapt to new host of poultry, they would die out. LPAI viruses have been environmentally sustained by close contact to LPAI viruses among wild birds when avian influenza A virus infections happened in endemic countries. Host species barriers do not mean simply the biological barriers [7]. Biological barriers between wild birds and poultry are almost the same in concerning about influenza binding receptor in cell membrane (α2–3-linked sialic acids) and replication condition in host temperature [19, 53]. In addition to biological barriers, interspecific interactions between wild birds (donor) and poultry (recipient), interactions between avian influenza viruses and poultry (recipient), and interactions among individuals of poultry (recipient) are considered as environmental barriers [7]. In consequence of surmounting these barriers, LPAI viruses have been sustained by the successful onward adaptation to new hosts like H7N7 viruses, H9N2 viruses and H7N9 viruses in the present [47, 59, 64]. If humans have been in close contact to poultry affected with LPAI viruses, asymptomatic or mild illness of avian influenza A virus infections would appear in humans but rarely leads to fatal disease [45, 46]. LPAI viruses suddenly have changed virulence to HPAI viruses and caused severe disease and deaths among poultry like the emergence of H5N1 virus being in consequent to human epidemic [14]. Increased virulence from LPAI to HPAI following antigenic shift could not be predicted before the happening. Avian influenza A viruses need to acquire the abilities to transmit to new host species and replicate effectively in new host before an epidemic or pandemic [7]. Antigenic shift in avian viruses has transmitted the abilities of transferring from poultry to humans and replicating progeny in humans by accumulated mutations in HA, NA, PB2, NS1, etc. but has not transmitted the abilities of transferring from human to human [28–38].

#### **3.2 Possibility of intermediate hosts or mixing vessels for the generation for pandemic influenza viruses**

Avian has α2–3-linked sialic acids, human has α2–6-linked sialic acids, and swine has both types of receptor for HA of influenza A viruses [80]. These enable

**103**

HPAI viruses.

**Figure 1.**

**and pandemic infections**

*Adequate Monitor of Avian Influenza Viral Infections and Foresight About Possibilities of Its…*

pigs to be susceptible to both human and avian influenza viruses. If a human influenza A virus infection and an avian influenza A virus infection happened simultaneously in swine, antigenic shift may produce new pandemic viruses which can be transmitted easily from person to person among human population with little or no immune response to them. In China, avian-like H1N1 and novel reassortant H1N2 influenza viruses from pigs were reported [81]. The swine H1N1 virus (A/swine/Zhejiang/1/07) was close to avian-like H1N1 viruses which is seemed to be derived from the European swine H1N1 viruses, and the two H1N2 viruses (A/ swine/Shanghai/1/07 and A/swine/Guangxi/13/06) were novel reassortant H1N2 influenza viruses containing genes from the classical swine (HA, NP, M, and NS), human (NA and PB1), and avian (PB2 and PA) lineage, which indicated that the reassortment of influenza viruses happened among humans, avian, and swine and the generation of new viruses was produced in swine [81]. In the analysis of influenza virus H1N1 pdm in 2009, the main persistent pdm/09-origin reassortant forms had at least five pdm/09-origin internal genes, and their surface genes were primarily of European avian-like (EA) or human H3N2-like swine influenza virus [82] (**Figure 1**). The monitor for a new pandemic virus is necessary to monitor and survey the epidemic infection in swine, in addition to monitoring of endemic LPAI infections among wild birds and poultry, epidemic LPAI and HPAI infections among wilds birds and poultry, and the following human infections by LPAI and

**4. Systemic monitor and approach for a new information of epidemic** 

Avian influenza viral infections are wide ranges of mammalians, and it is not enough to monitor avian, swine, and humans for covering all types of avian influenza virus infection because of the rare case appearance of the LPAI outbreak in cats in the USA [74]. The World Health Organization (WHO) continuously monitors avian and other zoonotic influenza viruses closely through its Global Influenza Surveillance and Response System (GISRS) (http://www.who.int/influenza/ gisrslaboratory/en/). From this site, necessary information about occurrence of outbreaks, conditions, widespread of infections, etc. can be investigated and gathered. But insufficient monitor for zoonotic influenza infections as potential to

*DOI: http://dx.doi.org/10.5772/intechopen.86551*

*Reassortant H1N2 influenza viruses and H1N1 pdm 2009 in swine.*

*Adequate Monitor of Avian Influenza Viral Infections and Foresight About Possibilities of Its… DOI: http://dx.doi.org/10.5772/intechopen.86551*

**Figure 1.** *Reassortant H1N2 influenza viruses and H1N1 pdm 2009 in swine.*

pigs to be susceptible to both human and avian influenza viruses. If a human influenza A virus infection and an avian influenza A virus infection happened simultaneously in swine, antigenic shift may produce new pandemic viruses which can be transmitted easily from person to person among human population with little or no immune response to them. In China, avian-like H1N1 and novel reassortant H1N2 influenza viruses from pigs were reported [81]. The swine H1N1 virus (A/swine/Zhejiang/1/07) was close to avian-like H1N1 viruses which is seemed to be derived from the European swine H1N1 viruses, and the two H1N2 viruses (A/ swine/Shanghai/1/07 and A/swine/Guangxi/13/06) were novel reassortant H1N2 influenza viruses containing genes from the classical swine (HA, NP, M, and NS), human (NA and PB1), and avian (PB2 and PA) lineage, which indicated that the reassortment of influenza viruses happened among humans, avian, and swine and the generation of new viruses was produced in swine [81]. In the analysis of influenza virus H1N1 pdm in 2009, the main persistent pdm/09-origin reassortant forms had at least five pdm/09-origin internal genes, and their surface genes were primarily of European avian-like (EA) or human H3N2-like swine influenza virus [82] (**Figure 1**). The monitor for a new pandemic virus is necessary to monitor and survey the epidemic infection in swine, in addition to monitoring of endemic LPAI infections among wild birds and poultry, epidemic LPAI and HPAI infections among wilds birds and poultry, and the following human infections by LPAI and HPAI viruses.
