# 6056
As new data becomes available the CDC routinely updates their interim guidance information on a variety of diseases, and the new H3N2v (variant) swine influenza virus - which as been detected in a handful of people across 5 states in recent months - is no exception.
On December 23rd we saw about a half dozen interim guidance documents released (see Three Would Make For A Crowded Viral Field), and again late yesterday (Jan 6th), another series of documents went online.
UPDATED: Guidance Documents Related to Preventing the Spread of Influenza A Viruses Friday, January 06, 2012 3:35:00 PM
UPDATED: Key Facts about Human Infections with Variant Viruses (Swine Origin Influenza Viruses in Humans) Friday, January 06, 2012 3:34:00 PM
UPDATED: Information on H3N2 Variant Influenza A Viruses Friday, January 06, 2012 3:34:00 PM
UPDATED: Variant (Swine Origin) Influenza Viruses in Humans Friday, January 06, 2012 3:33:00 PM
UPDATED: Information on Swine Influenza/Variant Influenza Viruses Friday, January 06, 2012 3:32:00 PM
For the most part, these documents provide background information, context, and a bit of advice for specific groups on the emergence of this new variant virus.
A few excerpts include:
What is Swine Influenza?
Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Swine flu viruses can cause high levels of illness in swine herds, but usually cause few deaths. Common signs in sick pigs include fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed. However, influenza-infected pigs also may not appear ill or be only mildly ill. Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks of seasonal influenza in humans.
What is a variant influenza virus?
When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus.” For example, if a swine origin influenza A H3N2 virus is detected in a person, that virus will be called an “H3N2 variant” virus or “H3N2v” virus. This naming convention was first announced in a January 6, 2012 Morbidity and Mortality Weekly Report entitled Update: Influenza A (H3N2)v Transmission and Guidelines — Five States, 2011. (See Box)
Can humans be infected with swine influenza viruses?
Yes. Swine flu viruses do not normally infect humans, however, sporadic human infections with influenza viruses that normally infect swine have occurred. When this happens, these viruses are called “variant viruses.” Most commonly, human infections with variant viruses have occurred in persons exposed to infected pigs (e.g. children near pigs at a fair or workers in the swine industry). In addition, there have been documented cases of multiple persons becoming sick after exposure to one or more sick pigs. Also cases of limited person-to-person spread of variant viruses have occurred.
While the number of confirmed cases remain small (about a dozen), the CDC is obviously concerned and has ordered enhanced surveillance, testing, and reporting around the country as to better gauge the prevalence of this virus.
Yesterday, in H3N2v Vaccine Trials, I wrote about efforts to develop a vaccine for this new strain should the need arise.
While it is likely that there are more cases out there going undetected, the good news is that so far we haven’t seen an explosion of flu cases (of any stripe) this winter - and this H3N2v flu does not appear to be any more virulent than regular flu.
Emerging viruses are important to track and monitor, however, because they can change over time. A relatively benign virus today need not necessarily remain so tomorrow.
So while the public health threat at this moment from this variant virus appears low, the CDC has reminded us repeated in recent weeks:
It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur.
While there is no evidence that sustained human to human transmission is occurring, all influenza viruses have the capacity to change and it's possible that this virus may become widespread.
Good enough reason to get your flu shot (to cover the other flu viruses out there), and to consistently practice good flu hygiene (cover coughs, wash your hands often, stay home if sick) this winter and spring.
