Second wave of A(H7N9) cases in the People's Republic of China peaked in weeks 4-6, 2014

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.

Rate of sporadic human H7N9 infections appears to be declining

Earlier in February, I posted a chart showing the possible exponential growth of H7N9 cases in the People’s Republic of China (link). Exponential growth of infectious diseases among humans, however, can only occur if there is sustained human to human transmission. Although sporadic H7N9 cases have continued to be reported since early February, there has been no increase in number of family or local clusters that would signal sustained human to human transmission.  

Importantly, the number of sporadic H7N9 cases has recently started to decline as depicted by the 2-week moving average in the chart below.   Analysis of the data by reported onset dates indicates that the H7N9 infections started to decline about the middle of  Week 6,   about the same time that I posted the chart (link) with the projection of exponential growth of cases.