Cats Beware: Eating Tweety Bird May Be Hazardous to Your Health

Though buried among Christmas season headlines, the report of a veterinarian contracting an avian flu strain from a cat is, to me, highly significant. When people speak of avian influenza viruses it is the highly lethal H5N1 or H7N9 that are being discussed as these two viruses are high on many threat lists. 

In this incident, a New York City veterinarian caring for sick cats contracted the H7N2 virus which had not been known to infect cats before this event. It has been speculated the cat may have contracted it from a pigeon. It had been diagnosed in humans at least twice since 2002: once from someone involved in a Virginia avian outbreak and once before, interestingly, from a person in New York City without an unknown exposure. The veterinarian, like the two other human cases, recovered uneventfully and no secondary spread of this virus to other humans was detected via a robust surveillance operation conducted by the New York City Department of Health. 

This event, to those who track influenza, transcends the minor illness that results as it is an important example of how zoonotic flu viruses could take hold. These types of incursions into new species are important to study and the viral characteristics and changes that made such a jump possible should be compared to wild-type viruses that circulate in avian species. 

Influenza possesses many capacities that bestow it with the the capacity to cause cataclysmic (no pun intended) pandemics. Among these capacities, its ability to infect a variety of different types of animal species and shuffle viral genes inside them is probably the most valuable. Moving from birds to cats to humans is one such example. Indeed, the pandemic H1N1 virus has a complex genealogical origin that is a triple-reassortant virus that reassorted again. When a virus has a wide host range, it can take all sorts of turns and jumps some of which may lead to a human pandemic. These types of events can be predicted but the precision may not be perfect as our last pandemic emerged, not from China, but from Mexico.

While there has been a much needed focus on H5N1, we also know that H7 (H7N2, H7N3, H7N7, H7N9) flu viruses have an ability to jump into humans and, in the case of H7N9 cause severe disease. I wonder if the fact that multiple H7's have been making incursions into humans is a sign of what our next pandemic flu virus may be. Thus far, it appears the most prolific of these H7's, H7N9, has not changed substantially through its 4 waves of infection. 

While it appears that, fortunately, H7N2 does not lead to severe disease in humans this event should remind people of the prowess of flu viruses and the eternal vigilance needed to protect the human race from this extremely successful virus.

Why Did 5000 Chickens Almost Cross the Road?

Remember avian influenza? The deadly version of flu that passes from poultry to humans and has caused outbreaks in many nations, most notably China. While we were dealing with Ebola panic and now a severe seasonal influenza outbreak, these viruses continued to spread (despite the lack of headlines).

The latest version of avian influenza to generate concern is H7N9 which has infected about 500 people since March of 2013, killing one-third. Taiwan has had 4 imported cases. The virus is spread to humans through direct and indirect contact with poultry. Limited human-to-human spread may also occur.

Because of the connection with poultry, control measures are centered around delimiting exposure to potentially infected birds. This often involves closing markets, culling, and inspections. 

An ongoing dilemma in Hong Kong involved a plan to inspect all local chickens at a small checkpoint while the market is disinfected after a culling of close to 20000 birds because of the potential for H7N9's presence given imports from a mainland farm tested positive for the virus. This arrangement was not found to the liking of the farmers who believe it will prove too onerous for them to conduct business.

Their response was to threaten to release 5000 live chickens into the busiest streets of Hong Kong. Not only would that action cause a major calamity but if any of the birds are harboring H7N9 (or other avian influenza viruses that can infect humans) could potentially widen exposure which is traditionally restricted to market-goers. They have since rescinded the threat. 

This incident illustrates why infectious diseases are so important. In just this one snapshot, you see economics, commerce, trade, government, and healthcare all intermingled. The ripple effect of certain infectious disease can be far-reaching and touch on virtually all aspects of modern civilization. 

Sir William Osler once remarked that to know syphilis--which has the ability to cause disease in every organ system--is to know medicine; similarly, to know infectious disease is to know the world.

Would Penguins Taste like Chicken to Bird Flu?

In the movie Mr. Popper's Penguins there's a scene in which the main character and his family are "rescuing" a group of penguins from the zoo. As they leave, they yell something to the effect of "arctic bird flu infectious disease emergency!" to facilitate their escape. 

While penguins can contract influenza, they are not the main concern with respect to a future bird flu pandemic as their exposure to humans is minimal. 

Currently, mankind is faced with dual threats from avian influenza: H5N1 and H7N9 (though other avian strains have kept into humans). These viruses, contracted by poultry exposure, have extremely high mortality rates but have not been able to spread efficiently between humans--the precondition for a pandemic.

H7N9 has been a relatively new threat that emerged in 2 waves in China (with subsequent cases imported to Taiwan) beginning last year. To date 238 cases have occurred with 57 deaths. This past week, China reported 45 new cases. 

In its latest risk assessment, the WHO anticipates more human cases possibly tied to the celebrations associated with the Chinese Lunar New Year celebrations, which will involve larger scale transportation of poultry. The ability of the virus to gain the ability to spread from human to human is unlikely.

Unfortunate for us, viruses like H7N9 reside in bird species with which humans have regular contact and not penguins--no offense to the natural or Pittsburgh variety.