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.