Emerging Influenza Viruses

”Avian influenza” is an ecological classification that does not correspond exactly to other classification schemes. outbreaks of influenza have been recognized in domestic poultry for many years. Avian influenza strains in domestic chickens and turkeys are classified according to disease severity, with two recognized forms: HPAI, also known as fowl plague, and LPAI. Avian influenza viruses that cause HPAI are highly virulent, and mortality rates in infected flocks often approach 100%. LPAI viruses are generally of lower virulence, but these viruses can serve as progenitors to HPAI viruses. All HPAI strains identified to date have involved H5 and H7 subtypes. Human infections caused by avian strains have been associated with both HPAI and LPAI strains. Evidence that HPAI strains arise from LPAI strains has led the World Organization for Animal Health (OIE) to classify all H5 or H7 strains as notifiable (OIE , 2005). Most hospitalized patients with AI H5N1 progress rapidly to ARDS, requiring ventilatory support within 24-48 hours of admission (Beigel et al., 2005)For patients who initially present with severe illness or whose condition begins to deteriorate, initiate oseltamivir as soon as possible. For patients with severe or deteriorating illness, treatment should be provided even if started later. where oseltamivir is unavailable or cannot be used for any reason, zanamivir may be given. This recommendation applies to all patient groups, including pregnant women, and all age groups, including young children and infants (WHO, 2009d).