For the purposes of this discussion the current outbreak of H7N9 began November 1, 2016 and is still continuing. More than 460 human cases have been reported from China. Of these cases, 426 have symptom onset dates reported by the World Health Organization (WHO) for cases with onset before February 10, 2017.
Graphing the symptom onset dates for these H7N9 cases provides a count of new daily infections of H7N9. Also included in the graph are the remaining 37 cases based on their reporting date rather than symptom onset date which is not available at this time for cases reported after February 11. The graph, an epidemic curve, shows that the greatest number of H7N9 infections occurred on February 1, 2017, based on a five day moving average.
Even if The 37 cases for which symptom onset dates are not available are distributed over the 17 days following February 11, they are an insufficient number of new cases to exceed the five-day moving average which peaked above 10 cases per day on February 1, 2017. The number of human H7N9 infections in this outbreak now seems to be declining. The decline in human cases can be attributed to closing of some local poultry markets by Chinese authorities. Hopefully, the number of H7N9 infections will continue to decrease.
While there is little evidence of human-to-human transmission in this outbreak, every human H7N9 infection is a potential opportunity for the influenza virus to reassort and become transmissible between humans.