J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016

 Cats Infected With H7N2 - NYC 2016

#13,657

Almost two years ago - (Dec 15th, 2016) - the New York City Health Department issued an unusual Statement On Avian H7N2 In Cats at a Manhattan animal shelter.

While cats are known to be susceptible to some novel flu strains (see Catch As Cats Can) this outbreak was remarkable due to its size (initially involving 45 cats), its location (NYC), and the virus involved - a relatively uncommon avian LPAI H7N2 virus not seen in the United States in over a decade. 

The plot continued to thicken over the next few weeks when 7 days later, the NYC DOH released a statement announcing a mild Human H7N2 Infection in a veterinarian who was treating sick cat. Eventually, more than 400 cats - across multiple facilities - were said to have been infected.  

LPAI H7N2 infection in humans has only rarely been reported, with only a couple of cases on record in the United States (in 2002 and 2003), and 4 people who were presumed to have been infected in the UK in 2007 following local outbreaks in poultry.

In all cases, illness was described as mild and self limiting.

At the time, the CDC wrote:

Why is CDC concerned about H7N2?

As part of CDC’s mission to protect the public from emerging health threats, CDC monitors changes in flu viruses found in human and animal populations. Finding a bird flu virus in an unexpected animal, like a cat, is always concerning, because it means the virus has changed in a way that may pose a new health threat. Animal viruses that gain the ability to infect humans are especially concerning because most people will not have existing immune protection against such viruses.

Also, there is potential for a pandemic (a global outbreak of disease) to occur when a new animal virus gains the ability to infect humans and also has the ability to spread efficiently from person to person. For these reasons, these incidents must be carefully investigated and appropriate actions taken to ensure that there is no ongoing spread of the novel virus among people.

Since then, we've learned a good deal more about the H7N2 virus, including:

• Last May, in J. Virology: Virulence Of A Novel H7N2 Virus Isolated From Cats In NYC - Dec 2016, we saw a follow up report on the NYC outbreak, which found the H7N2 virus will require additional adaptation before it poses a substantial human health threat.   
• Last December, the EID Journal: Characterization Of A Feline Influenza A(H7N2) Virus, researchers found:

Direct contact transmission of feline H7N2 subtype viruses was detected in ferrets and cats; in cats, exposed animals were also infected via respiratory droplet transmission. These results suggest that the feline H7N2 subtype viruses could spread among cats and also infect humans. Outbreaks of the feline H7N2 viruses could, therefore, pose a risk to public health.

• And in November of last year, in EID Journal: Avian H7N2 Virus in Human Exposed to Sick Cats,we saw another study that found the human H7N2 virus bound to both α2,6-linked (mammalian) and α2,3-linked (avian) sialic acids, an important trait for any species jumping avian flu virus to acquire, although virulence remained low.

Although the study doesn't appear to be available online yet (a `Production in progress' notice appears when I click the link), PubMed.gov has published the following abstract indicating at least one other animal worker exposed to H7N2 infected cats in NYC showed serological evidence of prior infection, and 5 others exhibited low positive titers to the virus, indicating possible infection.

J Infect Dis. 2018 Nov 5. doi: 10.1093/infdis/jiy595. [Epub ahead of print]

Detection of Avian Influenza A(H7N2) Virus Infection Among Animal Shelter Workers Using a Novel Serological Approach-New York City, 2016-2017.
 
Poirot E1,2, Levine MZ1, Russell K1, Stewart RJ1, Pompey JM1, Chiu S1, Fry AM1, Gross L1,3, Havers FP1, Li ZN1, Liu F1, Crossa A2, Lee CT1,2, Boshuizen V1,4, Rakeman JL2, Slavinski S2, Harper S1,2, Gould LH2.

1Centers for Disease Control and Prevention, Atlanta, Georgia.2New York City Department of Health and Mental Hygiene, New York.3Battelle, Atlanta, Georgia.4University of Oklahoma School of Community Medicine, Tulsa.

Abstract

Background:

In 2016, an influenza A(H7N2) virus outbreak occurred in cats in New York City's municipal animal shelters. One human infection was initially detected.

Methods:

We conducted a serological survey using a novel approach to rule out cross-reactive antibodies to other seasonal influenza viruses to determine whether additional A(H7N2) human infections had occurred and to assess exposure risk.

Results:

Of 121 shelter workers, one had serological evidence of A(H7N2) infection, corresponding to a seroprevalence of 0.8% (95% confidence interval, .02%-4.5%). Five persons exhibited low positive titers to A(H7N2) virus, indicating possible infection; however, we could not exclude cross-reactive antibody responses to seasonal influenza viruses. The remaining 115 persons were seronegative. The seropositive person reported multiple direct cat exposures without using personal protective equipment and mild illness with subjective fever, runny nose, and sore throat.

Conclusions:

We identified a second case of A(H7N2) infection from this outbreak, providing further evidence of cat-to-human transmission of A(H7N2) virus. 

For now avian H7N2 doesn't appear to be ready for prime time, but it - like all influenza viruses - continue to evolve and adapt, and at some point could accrue the right genetic changes to pose a genuine public health threat.   

Add in its ability to spread rapidly in companion animals, and their ability to further spread the virus on to humans, and you have a virus very much worth keeping our eye on.