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H7N9: Pandemic Potential?

Have you heard of H7N9? It’s a new avian influenza virus, and it has good reasons to be making people worried. Early last year, the virus was first found in people in China. There it’s been found in poultry (domestic birds like chickens, ducks, and geese) and is thought to be primarily spread through contact with these infected birds. Because it hasn’t been detected outside of China (yet), it’s received limited attention by the media in the rest of the world. But, concerningly, it may have some limited ability to be transmitted from person-to-person. And what’s causing even more alarm is its mortality rate – around one-third of people who become infected have died because of the infection.

H7N9 influenza A avian
The H7N9 influenza virus (as seen through an electron microscope). (Image credit: Centers for Disease Control and Prevention)

Last year, in the original outbreak there were 135 people total confirmed to have been infected with the H7N9 strain, and 44 of these people died. The infections, which began in March 2013, became less frequent as the year progressed, which is unsurprising because Chinese authorities took certain control measures (such as closing live bird markets) and avian influenza viruses (like the seasonal flu) have a seasonal pattern, circulating more in cold weather and less in warm weather. But, unfortunately, the number of cases (not unexpectedly) increased as the weather grew cold again, starting in October. Since the beginning of the new year, there have already been 40 new people confirmed to be infected with the virus, which the Centers for Disease Control and Prevention (CDC) is now saying has “pandemic potential.”

So what about the H7N9 virus makes it so unusual and dangerous? H7N9 has definitely been around before the 2013 outbreak in China, although before this it’s only been found in birds. To make matters more complicated, it’s hard to detect the virus in birds because not only do they not die from infection, but they don’t even show any visible symptoms – this makes tracking the virus, and coming up with effective control measures, very difficult. Also, people are rarely infected with this type of virus (H7 viruses) – there’s concern that this strain has developed some adaptations specifically for infecting mammals. Lastly, previously when people were infected with H7 viruses, the infections were usually mild, unlike the fatal respiratory infections and multiple organ failures seen with H7N9. The unusual behavior of this virus, with its unexpectedly high fatality rate, has experts puzzled and concerned.

While H7N9 has not been detected outside of China, the CDC warns that the virus may enter the U.S. at some point (likely from a traveler). Currently, H7N9 has spread mostly through contact with infected poultry, but because influenza viruses can change rapidly, there’s concern that H7N9 could change into a form that is more easily transmitted between people. If such a mutation takes place, this would greatly increase H7N9’s pandemic potential.

Currently, multiple different vaccines are at different stages of testing, but there is not a vaccine widely available yet. It’s also been seen that the H7N9 virus can rapidly develop resistance to antiviral medicine, and continue to cause life-threatening infections during the treatment. Taken together, this makes preventing and treating infection a real problem.

On top of all of this, the Chinese Lunar New Year (January 31) is fast approaching – it’s estimated that over 200 million people have already started traveling this week in preparation for the gigantic festival. There are concerns that travelers – especially anyone visiting live bird markets – may increase infection rates.

So while “out of sight, out of mind” might be an easy way to approach life, when thinking about H7N9 and other potential pandemics it’s good to remind ourselves that we can all affect – and infect — each other. And the world is becoming increasingly smaller as international travel becomes more commonplace.


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