# 5818
The Pennsylvania Department of Health has updated their FAQ sheet (Q & A: Novel Influenza A Virus) on the recent detections of a reassorted H3N2 swine flu virus in three children who attended a county fair in mid-August.
It is still very early in the epidemiological investigation of these cases, and there are a lot of questions yet to be answered.
Prime among those is whether this virus has the potential to spread efficiently in humans.
For now, evidence of sustained human transmission has not been found. Of course, the CDC is still investigating, and that could change if more cases show up.
But it is important to note, that even if a few more cases were to show up over the next few weeks, that wouldn’t necessarily mean that we are faced with an epidemic or pandemic situation.
For that to happen the virus would need to be adapted well enough to human physiology to have an R0 number (basic reproductive number) sufficient to sustain an outbreak.
The R0 number signifies the average number of secondary infections caused by one infectious person entering a totally susceptible population.
If less than 1.0, outbreaks are likely to sputter and die out. If greater than 1.0, the outbreak is more capable of spreading.
And as we’ve seen with roughly 20 other reported novel swine infections since 2005, and with a significant number of H5, H7, and H9 avian flu infections, it is possible to have limited outbreaks of a novel flu virus without it sparking an epidemic.
We’ll need to wait for more epidemiological evidence before we can know whether this particular virus has `legs’. If it is spreading efficiently (and that’s still a big `if’), we ought to see evidence of that fairly soon.
It is also possible that if this virus isn’t ready for prime time right now, that through further reassortment or mutation, it could become better adapted down the road. The only constant with influenza viruses is change.
So this situation deserves ongoing surveillance.
But regardless of this virus’s fate, the risks of seeing another novel pandemic virus emerge sometime in the future from either the farm or the wild are genuine.
A few recent blogs on this possibility include:
Professor Peter Doherty On Bird Flu
Two Reassortment Studies To Ponder
Hong Kong: Influenza Surveillance In Pigs
The (Swine) Influenza Reassortment Puzzle
The CDC’s investigation into these recent novel flu cases in Pennsylvania continues, and hopefully we’ll know more shortly.
Below are some excerpts from yesterday’s (9/6/11) updated Health Department FAQ.
Questions & Answers: Novel Influenza A Virus
About the Flu Virus/Current VaccinationWhat is this novel influenza A virus?
•
Influenza A viruses occur in many animals, including humans, swine (pigs) and wild birds.This particular virus is unique from other previous H3N2 human infections in that it also contains a genetic piece of the 2009 H1N1 virus.
• Is it possible for humans to transmit it to other humans?
Currently, it does not appear the virus is spreading from person‐to‐person. However, we will continue to learn ore as our investigation into this new virus continues.
•How serious is this virus?
We currently know of three cases of this novel influenza virus. One patient has recovered and the other two are recovering. Our investigation will continue to focus on the seriousness of the virus. Based on what we know about other types of flu, illness can range from very mild symptoms to death in particularly susceptible populations (like older people, young children and those with certain medical conditions).• What does this mean for this year’s flu vaccines? Will the current vaccine cover both seasonal flu and this new strain of flu?
The 2011‐2012 vaccine is the same as last year, covering two strains of influenza A pandemic H1N1 and a H3N2 strain that has been circulating for a few years now) as well as a strain of influenza B. It is too early to tell whether or not this new strain will even need vaccination.
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Should we be concerned that a flu pandemic is pending?
A pandemic is a global outbreak of disease. A flu pandemic happens when a new strain of the flu virus appears for which people have little or no immunity. As a result, it spreads easily from person to person around the world, causing widespread illness and death.
Currently, we don’t have any evidence to support that this novel influenza A virus will lead to a pandemic, as we haven’t yet been able to prove that it is being transmitted from human to human.
As with any new influenza A virus, public health officials are working to learn more about the source of this particular strain and to determine how/if it can be spread from person to person.
