faulker024

Based on illness onset dates from January through the end of November 2016, China officially reported about 115 human cases H7N9 infection. Over the course of several days in early January 2017, China notified the World Health Organization of more than 100 additional human cases of H7N9 presumably having been infected in December 2016. It appears that almost as many people were infected in December as all of the preceding months in 2016. The graph below shows the distribution of H7N9 cases by onset date where available and then by reporting date. The graph clearly shows the large increases in the number of infected individual reported recently. Should this increase be a cause for alarm? Increases in human cases of avian influenza always increase the risk for sustained human to human transmission of the disease. Reviewing the minimal data that is available for the 107 recent cases reported by China, some observations can be made. About 36% of these new cases are female and 67% are male...

In 2014, 366 human cases of avian influenza infection from four subtypes, A(H7N9), A(H5N1), A(H5N6) and A(H10N8) were reported from 7 countries, China, Egypt, Taiwan, Malaysia, Cambodia, Indonesia, and Vietnam. The case-fatality risk ranged from possibly as low as .22 to as high as .67 among these subtypes in 2014. There is no evidence among any of these subtypes of sustained human-to-human transmission. Influenza viruses that easily circulate among human populations are referred to as seasonal influenza viruses and can cause severe illness in 3 to 5 million individuals annually.[1] Avian influenza Type A viruses that cause infection in birds are referred to as avian influenza viruses. These viruses occur naturally among wild birds worldwide and can infect domestic poultry and other bird and animal species.[2] These avian influenza viruses circulating in bird populations do not usually infect humans. However, sometimes humans can become infected with avian influenza subtypes which hav...

It is well known that non-pandemic influenza has a seasonal repeating periodicity, especially in temperate climates [1]. The causes of seasonal cycles of influenza infections are not well understood. However, an analysis of seasonality of influenza around the world in a recent PLOS article indicates that cold-dry and humid-rainy conditions are associated with peaks in the frequency of seasonal influenza cases in different regions [2]. The authors in this article suggest that “these two distinct mechanisms account for influenza seasonality in temperate and tropical climates, perhaps due to changes in the dominant mode of transmission.” In the past decade there have been several outbreaks of novel influenza infections, including (A)H5N1, (A)H7N9, and (A)H10N8. Based on limited data, it does appear that novel influenza infections follow the same seasonal pattern as non-pandemic influenza. For example, H7N9 was first reported by the Republic of China to the World Health Organization (WHO) ...

The graph below shows the frequency of A(H7N9) cases by week number (based onset date) since week 47 in 2013.   The infection rate started to increase in the last week of December, 2013 and the first week of January 2014. The case count continued to climb and peak between weeks 4 through 6. Since then, the number of H7N9 cases has been declining perhaps signaling an end to the second wave of H7N9 infections in China.