As information about this year's unusually active (and early) H7N9 epidemic continues to trickle out of China we've seen updates, advisories, and statements coming from a variety of public health agencies around the world. This week alone we've seen:
To this expanding list we can add our own CDC, which posted the following assessment this afternoon. While we haven't seen evidence of efficient human-to-human transmission of this virus, the CDC is quite frank about H7N9's pandemic potential.
First today's statement, then I'll return with a bit more.
Human infections with a new avian influenza A (H7N9) virus (“H7N9”) were first reported in China in March 2013. Annual epidemics of human infections with H7N9 viruses in China have been reported since that time. Studies indicate that avian influenza viruses, like seasonal influenza viruses, have a seasonal pattern: they circulate at higher levels in cold weather and at lower levels in warm weather. As of January 16, 2017[PDF - 382 KB, 9 pages], cumulative reported human infections with H7N9 totaled 918 with 359 deaths.
Most human infections with H7N9 have occurred after exposure to poultry; H7N9 viruses continue to circulate in poultry in China. Most reported patients have had severe respiratory illness; about one-third of patients have died. Rare, limited person-to-person spread of this virus has been identified in China, but there is no evidence of sustained person-to-person spread of H7N9. Some cases of H7N9 have been reported outside of mainland China but most of these infections have occurred among people who had traveled to China before becoming ill. H7N9 viruses have not been detected in people or birds in the United States.
It’s likely that sporadic human infections with H7N9 associated with poultry exposure will continue to occur in China. It's also possible that H7N9 may spread to poultry in neighboring countries and that human cases associated with poultry exposure may be detected in neighboring countries. It’s also possible that H7N9 cases may continue to be detected among travelers returning from H7N9-affected countries, even possibly in the United States. However, as long as there is no evidence of ongoing, sustained person-to-person spread of H7N9, the public health risk assessment would not change substantially.
Most concerning about this situation is the pandemic potential of this virus. Influenza viruses constantly change and it’s possible that this virus could gain the ability to spread easily and sustainably among people, triggering a global outbreak of disease (pandemic).
Click here for Influenza Risk Assessment Tool Results for H7N9 »In fact, of the influenza viruses rated by the Influenza Risk Assessment Tool (IRAT), H7N9 is ranked as having the greatest potential to cause a pandemic, as well as potentially posing the greatest risk to severely impact public health.
The U.S. Government supports international surveillance for H7N9 and other influenza viruses with pandemic potential. CDC is following the H7N9 situation closely and coordinating with domestic and international partners. Most important, CDC takes routine preparedness actions whenever a new virus with pandemic potential is identified, including developing candidate vaccine viruses to use for vaccine production in case vaccine is needed. Those preparedness measures continue. CDC also has issued guidance to clinicians and public health authorities in the United States, as well as provided information for people traveling to China. CDC will provide updated information as it becomes available.
Between the inevitable delays and barriers to reporting brought on by this weekend's Chinese New Year's celebration, and some built in reluctance on the part of the Chinese to release timely information, our ability to track this epidemic is limited.
For now, our best gauge is probably the alert level maintained by Hong Kong's CHP. If they should start reporting a surge in imported cases, or suddenly raise their pandemic alert level, we should begin to pay very close attention.With influenza, there is no script for the virus to follow, and no predictable curve for us to plot. It does whatever it does, when it does it. And we always find out after the fact.
All I'll predict is that between H7N9 in China, and multiple flavors of HPAI H5 spreading around the world, the next few months are going to be busy ones.