Credit CDC
# 7368
From the Annals of Internal Medicine we get a letter – published June 4th - from researchers at the Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, China that looks at the characteristics of 24 recent H7N9 fatalities in China.
The letter is freely available, and I’ve only excerpted a small portion below.
The authors found that most deaths occurred in patients over the age of 60, suggesting this is a risk factor. They find the virus isn’t easily transmitted, but that once a person is infected, the clinical course progresses rapidly.
Follow the link to read:
Deaths Associated with Avian Influenza A(H7N9) Virus in China
Yuehua Ke, PhD, MD; Yufei Wang, PhD, MD; Wenyi Zhang, MD; Liuyu Huang, PhD; and Zeliang Chen, PhD, MD
Ann Intern Med. Published online 4 June 2013 doi:10.7326/0003-4819-159-2-201307160-00669
(EXCERPT)
Discussion: Infection of humans by novel influenza A viruses that are distinct from circulating viruses and produce severe disease can lead to sporadic human infections or influenza pandemics (4 - 5). Therefore, the recent discovery of the H7N9 virus is of great public health interest. Because most of the deaths we report occurred in patients aged 60 or older, it is reasonable to consider this demographic at high risk while we learn more about age distribution. In addition, the illness progresses rapidly after symptoms first appear; therefore, in suspected cases clinicians should plan to test for the diagnosis and treat early.
The current case-fatality rate for H7N9 infection is 19%, which is much higher than that for seasonal influenza and pandemic H1N1 influenza (0.1% to 1%), but lower than that for avian influenza H5N1 (40% to 60%). However, the case-fatality rate for H7N9 infection should decrease as we learn more about the disease because cases with more severe illnesses are identified earlier in the study of most new diseases.
Moreover, no H7N9 virus infections were found among close human contacts of the patients who died, which may allow us to worry a little less about human-to-human transmission of this virus.
Collectively, our data suggest that H7N9 virus infection has a relatively high case-fatality rate and progresses rapidly from symptom onset to severe illness and death. Therefore, clinicians should start antiviral treatment when infection with H7N9 virus is first suspected.
Chinese researchers continue to release detailed information on their H7N9 outbreak with remarkable speed. A mindset that we can only wish the Saudi’s would adopt with their emerging MERS virus.
The unanswered question right now is how many mild, or asymptomatic infections there have been with the H7N9 virus (see H7N9: CFR Considerations).
If infection is rare, and surveillance is picking up the bulk of them, then this is indeed a very deadly flu virus.
But if there are hundreds of cases going undetected, as researchers at the University of Hong Kong have proposed (see H7N9: Trying To Define The Size Of The Iceberg) then the real case fatality rate could be far lower than it currently appears.
It is worth noting at this point that the CFR of the Spanish Flu of 1918 – at least in the United States and most of Europe – was about 2%, or 1/10th the apparent fatality rate of this emerging virus.
Which means we could be an order of magnitude too high on calculating the fatality rate, and still be facing a formidable viral foe.
Which is why so much attention has been focused on the H7N9 outbreak in China. While we are seeing a lull in cases right now, officials are anxiously waiting to see what happens with this virus when cooler weather returns in the fall.
