Credit WHO
# 7616
Like many other diseases that plague mankind - influenza didn’t begin in humans - its original host species appears to be waterfowl. But gradually, and probably as a result of the domestication of ducks and geese thousands of years ago, it made its way into man and other species.
What once was predominantly an avian virus can now be found circulating in humans, canines, swine, equines, and even some sea mammals.
This intersection of man and other species, and their sharing of viruses (zoonotic transmission), has increasingly been recognized as a driving factor in emerging infectious diseases, and even the creation of pandemics.
The age of emerging infectious diseases in humans really began in earnest about 10,000 years ago when humans began to domesticate – and live in close proximity to – other animals (see The Third Epidemiological Transition).
Tuberculosis, which now infects 1/3rd of humanity, likely jumped from domesticated goats and cattle. Measles probably evolved from canine distemper and/or the Rinderpest virus of cattle.
Other zoonotic nasties include Babesiosis, Borrelia (Lyme), Nipah, Hendra, Malaria, Hantavirus, Ebola, Leptospirosis, Q-Fever, bird flu . . . the list is long and growing.
Roughly 70% of the infectious diseases that afflict man are believed to have begun in some other species, and new ones (think MERS-CoV, H7N9, H5N1, SFTS, etc. ) continue to show up each year.
Yesterday the World Health Organization updated their monthly Influenza at the human-animal interface, that looks at recent activity in zoonotic influenza viruses.
A few highlights below, but follow the link to read it in its entirety.
Summary and assessment as of 29 August 2013
Human infection with avian influenza A(H5N1) viruses
From 2003 through 29 August 2013, 637 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries, of which 378 died.
Since the last update on 4 July 2013, four new laboratory-confirmed human cases with influenza
A(H5N1) virus infection were reported to WHO from Cambodia. One of these died.
All cases are considered to be sporadic cases, with no evidence of community-level transmission. As influenza A(H5N1) virus is circulating widely in poultry in Cambodia, additional sporadic human cases or small clusters might be expected in the future.
Table 1: Laboratory-confirmed human cases of avian influenza A(H5N1) virus infection (4 July 2013- 29 August 2013)
Overall public health risk assessment for avian influenza A(H5N1) viruses: Whenever influenza viruses are circulating in poultry, sporadic infections or small clusters of human cases are possible, especially in people exposed to infected household poultry or contaminated environments. However, this influenza A(H5N1) virus does not currently appear to transmit easily among people as such, the risk of community-level spread of this virus remains low.
Human infection with other non-seasonal influenza viruses
Avian influenza A(H7N9)China has reported two cases of human infection with avian influenza A(H7N9) virus since the last
update of 4 July 2013. The first patient was a 61-yr-old woman from Hebei Province who had onset of illness on 10 July. The second was a 51-yr-old woman from Guangdong province with onset on 27 July 2013. As of 16 August 2013, 135 human cases with influenza A(H7N9) infection were reported to WHO, including 44 deaths. Most human cases presented with pneumonia.
Most human A(H7N9) cases have reported contact with poultry or live animal markets. Knowledge about the main virus reservoirs and the extent and distribution of the virus in animals remains limited.
Given the reports of additional human cases, combined with the likely continued circulation of the virus in poultry, reports of additional human cases and infections in animals would not be unexpected, especially as the Northern Hemisphere autumn approaches.
Although four small family clusters have been reported among previous cases, evidence does not
support sustained human-to-human transmission of this virus.
Influenza A(H3N2) variant virus infections in humans
The United States of America (USA) reported 16 cases of human infection with influenza A(H3N2)v this year in Illinois (1), Indiana (14) and Ohio (1). Only one person was hospitalized and no deaths have occurred. All cases reported close contact with swine in the week before illness onset and no ongoing human-to-human transmission has been identified.
Limited serological studies indicate that adults may have some pre-existing immunity to this virus
but children do not. Seasonal vaccines do not provide cross-protection to influenza A(H3N2)v in adults or children. Three candidate vaccine viruses specific for A(H3N2)v have been developed in the USA and could be used to produce an (H3N2)v vaccine if needed.
Overall public health risk assessment for influenza A(H3N2)v viruses: Further human cases and small
clusters may be expected as this virus is circulating in the swine population in the USA and the season of
agricultural fairs is ongoing.
Close monitoring of the situation, including continued characterization of viruses to detect any changes, is warranted.
We live in an amazingly complex and interconnected world, where what happens in a live poultry market in China, a pig operation in Belarus, or even at a cockfight in Indonesia can ultimately impact the health of people around the world.
Oceans and long distances are no longer barriers to the spread of diseases. An emerging virus can literally hop a plane in Beijing, and be in New York or London in less than 24 hours.
So we watch these spillovers of diseases from animals to humans – no matter how small they may first appear to be – with extreme interest. As we saw in 2009 with the novel H1N1 virus, given the right conditions, a new virus can sweep the world in a matter of months.
