|Credit Archives of Public Health|
Perhaps the most striking aspect of novel flu in the 21st century is how much faster new subtypes are emerging, compared to the last century. While some of this might be attributable to better surveillance and improved laboratory tests, the timeline above makes a pretty good case that the rate of new emerging flu viruses is accelerating.
And these are only the novel flu viruses that are known to have infected humans. We've also got our eyes on a growing list of recently emerged (or discovered) flu viruses in the wild that haven't jumped to humans (yet).
And influenza is just part of the picture, as zoonotic diseases (Zika, Dengue, Nipah, MERS, SARS, Avian flu, etc.) have been on the increase around the globe for the past couple of decades (see Viral Creep In Second Decade Of The 21st Century).
This trend was predicted more than 20 years ago by noted anthropologist and researcher George Armelagos (May 22, 1936 - May 15, 2014) of Emory University, who proposed that we are entering an era hallmarked by newly emerging infectious diseases, re-emerging diseases carried over from the 2nd transition, and a rise in antimicrobial resistant pathogens.
All three of which have gained global attention in the past two decades. You can read about his theory in my 2011 blog The Third Epidemiological Transition.
Tracking the evolution and epidemiology of novel flu viruses going back almost 100 years (to 1918), we've got an open-access letter to the editor of the Archives of Public Health, by Chau Minh Bui, Abrar Ahmad Chughtai, Dillon Charles Adam and C. Raina MacIntyre.
This detailed and highly informative letter is far too long to do it any kind of justice here, so I'll simply post the link and abstract. A few highlights you'll encounter, however, include:
- Genetically distinct influenza A reassortants have emerged in humans on a total of 19 separate occasions since 1918.
- Of these, 6 strains are able to be efficiently transmitted from human-to-human, 10 are predominantly zoonotic AIVs, and 3 are predominantly zoonotic swine influenza variants.
- Most zoonotic AIVs (6 of 10) and all 3 swine influenza variants typically cause mild infections in humans (see Table 1). Severe illness and fatalities are associated with only four zoonotic AIVs: high death rates have been reported for human infections with H5N6 (9/15 cases, 60%), H10N8 (2/3 cases, 67%), H7N9 (314/791 cases, 40%), and H5N1 (449/850, 53%).
Follow the link to download and read the full report.
An overview of the epidemiology and emergence of influenza A infection in humans over time
Chau Minh BuiEmail author, Abrar Ahmad Chughtai, Dillon Charles Adam and C. Raina MacIntyre
Archives of Public Health The official journal of the Belgian Public Health Association 201775:15
© The Author(s). 2017
In recent years multiple novel influenza A strains have emerged in humans. We reviewed publically available data to summarise epidemiological characteristics of distinct avian influenza viruses known to cause human infection and describe changes over time. Most recently identified zoonotic strains have emerged in China (H7N9, H5N6, H10N8) – these strains have occurred mostly in association with visiting a live bird market. Most zoonotic AIVs and swine influenza variants typically cause mild infections in humans however severe illness and fatalities are associated with zoonotic H5N6, H10N8, H7N9 and H5N1 serotypes, and the H1N1 1918 Spanish Influenza. The changing landscape of avian influenza globally indicates a need to reassess the risk of a pandemic influenza outbreak of zoonotic origin.