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Bird Flu – On the Move?

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In the last 11 months of 2013, there was a total of 144 confirmed cases of H7N9 infection in China, with 46 deaths. This case total was almost duplicated during one month — January of this year — during which 127 cases were reported. No evidence of sustained person-to-person spread of H7N9 has been found, though some evidence points to limited person-to-person spread in rare circumstances. No cases of H7N9 outside of China have been reported. The new H7N9 virus has not been detected in people or birds in the United States

Human cases of influenza due to the avian virus, H7N9, were first detected in February 2013 in China. During spring of that year, the World Health Organization (WHO) reported 132 human H7N9 infections, with 44 deaths, with most cases having illness onset during the month of April. The following month, however, the number of cases plummeted, likely as a result of both a change in seasons (like seasonal influenza, avian viruses circulate at higher levels in cold compared to warm weather) and control measures, including the closure of live bird markets. This respite was short-lived, with cases once again appearing in October and in January alone there was a total of 127 cases, with 44 deaths. These 127 cases were just 17 fewer than reported in all of 2013.

Contact with infected poultry accounts for almost all cases of infection, which can be asymptomatic. Serosurvey data from outbreak areas found no instances of seropositivity among 1129 general population subjects, while >6% of 396 poultry workers had a hemagglutination inhibition titer of ≥ 80. 1

Human-to-human transmission has occurred and an example is illustrated by a report of 15 cases from China received on February 7 and 9 of 2013. Thirteen had been exposed to live poultry. Of the 14...