Our analyses revealed that during late summer staging July-August and fall migration September-October , hatch year HY birds were more likely to be infected than after hatch year AHY birds, however there was no difference between age categories for the remainder of the year winter, spring migration, and breeding period , likely due to maturing immune systems and newly acquired immunity of HY birds. Probability of infection increased non-linearly with latitude, and was highest in late summer prior to fall migration when densities of birds and the proportion of susceptible HY birds in the population are highest.
In a few cases, bird flu has passed from one person to another. Only sporadic human cases have been reported since Health officials worry that a global outbreak could occur if a bird flu virus mutates into a form that transmits more easily from person to person. Researchers are working on vaccines to help protect people from bird flu. Signs and symptoms of bird flu may begin within two to seven days of infection, depending on the type.
In most cases, they resemble those of conventional influenza, including:. Some people also experience nausea, vomiting or diarrhea. And in a few cases, a mild eye infection conjunctivitis is the only indication of the disease.
See your doctor immediately if you develop a fever, cough and body aches and have recently traveled to a part of the world where bird flu occurs. Be sure to let your doctor know if you visited any farms or open-air markets.
Bird flu occurs naturally in wild waterfowl and can spread into domestic poultry, such as chickens, turkeys, ducks and geese. The disease is transmitted via contact with an infected bird's feces, or secretions from its nose, mouth or eyes.
Open-air markets, where eggs and birds are sold in crowded and unsanitary conditions, are hotbeds of infection and can spread the disease into the wider community. Undercooked poultry meat or eggs from infected birds can transmit bird flu. Poultry meat is safe to eat if it's been cooked to an internal temperature of F 74 C. Influenza A subtypes and B viruses are further classified by strains. The nomenclature for influenza virus isolates includes the influenza virus type A or B , host species omitted if human in origin , geographical site, serial number, year of isolation and, lastly, the H and N variants in brackets.
Influenza viruses have a single-stranded, negative-sense RNA genome and a pleiomorphic non-uniform envelope with a diameter of 50— nm. The influenza A and B virus genomes consist of 8 separate segments, each coding for 1 or several functionally important proteins required for virus entry, replication or virus structure.
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