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All H3N2 Flu Cases Had Contact with Pigs, Says CDC

10 August 2012, at 4:55pm

US - At a press briefing yesterday, 9 August, Joe Bresee from the influenza division at the Centers for Disease Control (CDC) provided an update on the status of the investigations into the increased number of reported cases of Influenza A H3N2 variant, or V virus. A total of 113 cases have been reported, all of whom had contact with pigs. Symptoms have been mild, with no deaths; two cases were admitted to hospital but have been discharged.

As of 3 August, Dr Bresee said, 12 new cases of V virus were reported from three states, Hawaii, Indiana and Ohio. These 12 cases brought the total number of confirmed cases at that time with this particular virus to 29. The virus was first detected in July 2011. Of these 29 cases, 16 had been reported since 12 July 2012. As expected, additional cases have been reported from areas where cases had been confirmed already, and a case had been reported from an additional state.

So as of 9 August, there are 145 confirmed cases of influenza infection with H3N2v virus, since the current outbreaks began in July of this year. This includes one case in Hawaii, one case in Illinois, 113 cases being reported from Indiana, and 30 cases being reported from Ohio. This is clearly a significant increase since the previous week’s total, so CDC thought it would be good to try to put this into context.

Confirmed cases have had exposure to swine, and most of these infections have occurred in people exhibiting swine, family members of exhibiters, people visiting swine barns at fairs, or people attending fairs where swine are present. The severity of human illness associated with this virus continues to resemble that of seasonal flu. Most cases are mild and self-limited and resolve on their own. Most cases have occurred in children. CDC has not received any report of deaths associated with H3N2v infection, and there have been two confirmed hospitalizations with H3N2v infection so far. Both patients have recovered and have been discharged.

Dr Bresee explained that, on 6 August, CDC provided guidance to state laboratories and are now allowing states to confirm their own H3N2v cases prior to laboratory confirmation at CDC. CDC had found that cases that were positive at the state level were overwhelmingly being confirmed also with CDC. So given this, and in the context of an outbreak situation with very little seasonal influenza circulating, CDC felt it was appropriate for states to report positives as confirmed cases rather than waiting for CDC confirmation. So positive samples will still be forwarded to CDC where they will be confirmed by genetic sequencing. The change in reporting requirements is expected to provide for a more real-time indication of how these outbreaks are evolving in states. CDC anticipates that most, if not all, presumptive positives reported by states will be confirmed also at CDC, which will keep those organisations updated.

He continued that CDC understands that people are concerned as to the rapid jump in the number of H3N2 cases compared with the previous week. There has been no evidence of sustained efficient human-to-human spread in the community. Seasonal influenza systems are active and not shown any sign of increase in influenza activity. This is not a pandemic situation. But of course, CDC is continuing to monitor the situation closely, and we'll provide updates frequently. Right now, a large number of agricultural fairs are ongoing around the country and direct exposure of people to infected pigs has been the primary cause of infections, from investigations conducted so far this year. So those preventive actions we've been recommending for people who are attending those fairs continue to be as important this week as it was last week.

In terms of what we can expect going forward based on what has been observed in recent weeks, it is likely further cases will be identified in the upcoming days, he said. It is also possible that sporadic infections, even localised outbreaks among people with this virus will occur in other parts of the countries with swine exposure. There are reports of influenza-like illness from other states, and CDC is looking into these along with the state health departments Finally, limited human-to-human transmission has been observed in the past and some limited human-to-human spread may be observed in these current outbreaks. Ongoing investigations will determine whether there is, and if so, what the extent of transmission is.

Again, while the cases so far have been mostly mild, as with seasonal flu, severe illness resulting in hospitalizations have occurred, and even death is possible. Persons with underlying chronic conditions that place them at increased risk with seasonal influenza are likely also at higher risk for complications from H3N2v infection. Persons with suspected H3N2v virus infection and at high risk of influenza complications, as well as hospitalized patients with suspected H3N2v infection should be treated with antiviral drugs as soon as possible. H3N2v virus is sensitive or susceptible to available prescription antiviral drugs, oseltamivir and zanamivir.

Dr Bresee stressed that there is guidance to the public but what CDC really wants to focus on is guidance to folks who will be exposed to pigs, especially in the setting of agricultural fairs. And the guidance is the same as the previous week:

  • Wash your hands frequently with soap and water before and after exposure to the animals.
  • Never eat or drink or put things in your mouth while in animal areas.
  • Never bring food or drink into animal areas.
  • If you are at high risk for flu infection like elderly, young children, people with underlying diseases, think about avoiding pig exposure altogether when you go to the fairs.
  • And finally, avoid close contact with animals that look or act ill when possible.

Whether you have pig exposure or not, he added, if you go to a doctor for flu symptoms following direct or close contact with swine, tell your doctor about the exposure. If you have flu symptoms, follow the CDC’s regular recommendations for seeking treatment for influenza, and more importantly, follow your doctor's recommendations. If you've had symptoms of flu or very sick or worried about your illness, contact your health care provider. They may wish to test you and treat you with an antiviral medication.

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