the different sites of infection (shown in red) of seasonal h1n1 versus avian h5n1 influences lethality , ability spread.
in general, humans catch humanized influenza virus (a human flu virus of type a) have symptoms include fever, cough, sore throat, muscle aches, conjunctivitis, and, in severe cases, breathing problems , pneumonia may fatal. severity of infection depends in large part on state of infected persons immune systems , whether had been exposed strain before (in case partially immune). no 1 knows if these or other symptoms symptoms of humanized h5n1 flu.
the avian influenza hemagglutinin binds alpha 2-3 sialic acid receptors, while human influenza hemagglutinins bind alpha 2-6 sialic acid receptors. means when h5n1 strain infects humans, replicate in lower respiratory tract, , consequently cause viral pneumonia. there yet no human form of h5n1, humans have caught far have caught avian h5n1.
the reported mortality rate of highly pathogenic h5n1 avian influenza in human high; data indicate 60% of cases classified h5n1 resulted in death. however, there evidence actual mortality rate of avian flu lower, there may many people milder symptoms not seek treatment , not counted.
in 1 case, boy h5n1 experienced diarrhea followed rapidly coma without developing respiratory or flu-like symptoms. there have been studies of levels of cytokines in humans infected h5n1 flu virus. of particular concern elevated levels of tumor necrosis factor-alpha, protein associated tissue destruction @ sites of infection , increased production of other cytokines. flu virus-induced increases in level of cytokines associated flu symptoms, including fever, chills, vomiting , headache. tissue damage associated pathogenic flu virus infection can result in death. inflammatory cascade triggered h5n1 has been called cytokine storm some, because of seems positive feedback process of damage body resulting immune system stimulation. h5n1 induces higher levels of cytokines more common flu virus types.
in birds
clinical signs of h5n1 in birds range mild - decrease in egg production, nasal discharge, coughing , sneezing - severe, including loss of coordination, energy, , appetite; soft-shelled or misshapen eggs; purple discoloration of wattles, head, eyelids, combs, , hocks; , diarrhea. first noticeable sign sudden death.
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