H3N2 Characterization – Credit CDC
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While the numbers remain small this summer, yesterday a new state (Illinois) reported a confirmed case of H3N2v (Swine variant) influenza in a human – bringing to 15 the total thus far in 2013 (previous reports: Ohio 1, Indiana 13).
Until a couple of years ago we rarely saw more than 3 or 4 human cases each year, but 2011 saw a dozen cases reported, and last year (2012) more than 300 infections confirmed - mostly in Midwestern states, and nearly all associated with attendance at county and state fairs.
Last year’s big spike in cases did not come until August, and so it is a little too soon to know how this year will compare. And a reminder: these numbers are likely an undercount of actual infections, as not everyone who gets sick seeks medical care, or gets tested.
The most commonly reported strain: H3N2v – a reassorted swine H3N2 virus which acquired the M (matrix) gene from the 2009 H1N1 virus - was first detected in humans in July of 2011.
While this virus appears no more severe than seasonal flu (which can sometimes be very serious) and does not as yet transmit in humans in a sustained and efficient manner, the CDC is nonetheless monitoring it closely.
This from the CDC’s H3N2v BASICs FAQ.
Why is CDC concerned about H3N2v?
CDC is concerned about H3N2v for a few reasons.
First, infections with influenza viruses (including variant viruses like H3N2v) can sometimes cause severe disease, even in healthy people. This can include complications (like pneumonia), which can require hospitalization, and sometimes result in death.
Second, this virus seems to spread more easily to humans from pigs than other swine influenza viruses.
Third, influenza viruses are always changing. It’s possible the H3N2v virus could change and begin spreading easily from person to person.
Fourth, studies conducted by CDC and others have indicated that children younger than about 10 years old have little to no immunity against H3N2v virus. Adults seem to have more immunity, perhaps because they might have been previously exposed to similar viruses in their lifetimes.
Is H3N2v dangerous?
Currently, the severity of human illness associated with H3N2v resembles that of seasonal flu.
Keep in mind that even seasonal influenza can be a serious disease. Sometimes seasonal influenza can lead to complications (like pneumonia). It also can lead to hospitalization and even death.
Next stop, the State of Illinois announcement on their H3N2v detection, then I’ll return with a little more.
FOR IMMEDIATE RELEASE
August 1, 2013
CONTACT:
Sabrina L. Miller
(312) 814-8194State Health Department Confirms H3N2v Influenza Case
Common flu precautions recommended
CHICAGO – The Illinois Department of Public Health (IDPH) laboratory has confirmed one case of what is known as the H3N2v influenza virus, which has now been reported in three states this year –Illinois, Indiana and Ohio. IDPH is working with local health officials to alert the public on ways to reduce the risk of transmission of this virus. The confirmed case is a Boone County child with mild symptoms who had contact with swine while helping an exhibitor at the DuPage County Fair which was held in late July.
H3N2v is a variant form of influenza A, which was first detected in swine in 2011 and the first human cases were reported in 2012, including four cases in Illinois. The CDC is currently reporting more than a dozen cases in the U.S. this year. All infections in 2013 have occurred in people following contact with swine, and cases of the virus being transmitted from person to person are rare. So far, the severity of illnesses associated with this virus in people has been similar to the severity of illnesses associated with seasonal flu virus infections.
“The H3N2v virus is relatively new, but the Illinois Department of Public Health, the Illinois Department of Agriculture and our federal partners are monitoring this situation closely,” said IDPH Director Dr. LaMar Hasbrouck. “We want you to enjoy your time at the state or county fair, so one key thing to do to stay healthy is to wash your hands frequently, especially if you are around swine.”
Tips to avoid influenza include:
- Wash your hands frequently with soap and water before and after exposure to animals.
- Do not take food or drinks into animal areas; do not eat, drink or put anything in your mouth while visiting animal areas.
- Do not take toys, pacifiers, cups, baby bottles, strollers or similar items into animal areas.
- Avoid close contact with animals, especially swine.
- Avoid contact with animals if you have influenza-like symptoms.
- Use caution when deciding to visit an animal area if you have an underlying health condition or if persons are younger than 5 years or older than 65 years or pregnant.
Influenza is contracted through droplets when an infected person or animal coughs or sneezes. Those droplets can either be inhaled or can be on a surface you touch with your hand, and then touch your mouth or nose.
Influenza symptoms include fever, cough, sore throat, runny or stuffy nose, body aches, headache and fatigue. Illness can last a week or two. Certain people have a higher risk of serious infection from influenza including the very young, elderly, pregnant women, people with weakened immune systems and those with asthma, diabetes and heart disease. If you have, or do come into contact with swine and are experiencing influenza symptoms, contact your health care provider.
On July 5th, the CDC released a HAN Advisory On H3N2v, alerting doctors to the possibility that more cases could turn up this summer.
Last month the CDC also released two new interim guidance documents on H3N2v for local public health agencies; one on case definitions, and the other on surveillance and specimen collection.
We’ll be checking the CDC’s FluView report later today for any other cases that may have been detected over the past week.
While the public health risk posed by these variant flu viruses appears low right now, emerging flu viruses can abruptly change, and so could that assessment.
Which is why we always pay particularly close attention whenever a novel (or variant) flu strain tries to jump to humans.
