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# 6517
The mantra of the CDC over the past few weeks regarding the H3N2v flu virus is that sustained and efficient transmission between humans has not been detected. They have allowed the possibility, however, that some limited person-to-person transmission may have occurred.
And today’s numbers, indicating just 52 new cases reported over the past week, continues to support that analysis.
While some cases may be going unrecorded, this total is lower than one would expect to see if the virus were being readily transmitted.
Good news for now, but with the caveats that surveillance by definition is a look backwards in time – not ahead - and this virus is still learning about human physiology.
Given enough opportunities - H3N2v could one day adapt to become a more formidable human pathogen.
Here then are some excerpts from today’s CDC FluView Report and their weekly H3N2v update:
2011-2012 Influenza Season Week 33 ending August 18, 2012
Novel Influenza A Virus:
From July 12 through August 23, 2012, a total of 276 infections with influenza A (H3N2) variant (H3N2v) viruses have been reported in ten states (Hawaii [1], Illinois [4], Indiana [138], Maryland [12], Michigan [5], Minnesota [1], Ohio [98], Pennsylvania [6], West Virginia [3], and Wisconsin [8]). So far during the current outbreaks, 13 confirmed cases have been hospitalized as a result of their illness; no deaths have occurred. The vast majority of cases have been associated with swine exposure though three likely instances of human-to-human transmission have been identified. At this time no ongoing human-to-human transmission has been identified. Public health and agriculture officials are investigating the extent of disease among humans and swine, and additional cases are likely to be identified as the investigation continues. Because of reporting deadlines, the state totals reported by CDC may not always be consistent with those reported by state health departments. If there is a discrepancy between these two counts, data from the state health departments should be used as the most accurate number.
H3N2v Update: New Cases Reported, Limited Person-to-Person Transmission Detected
August 24, 2012 -- Today, 52 additional cases of H3N2v are being reported, bringing the total number of such infections since July 2012 in the United States to 276 across 10 states. Investigations into H3N2v cases indicate that the main risk factor for infection is exposure to pigs, mostly in fair settings; however, CDC also is reporting three instances of likely human-to-human spread of this virus during the current outbreaks. Found in pigs in 2010 and first detected in humans in July 2011, this H3N2 variant virus appears to be more transmissible from pigs to people than other variant viruses. The Centers for Disease Control and Prevention (CDC) is working with states to respond to this evolving situation and continues to monitor the situation closely.
According to CDC’s Dr. Joseph Bresee “limited human-to-human spread of this virus has been seen in the past, but the H3N2v virus has not previously -- and is not now -- spreading easily from person-to-person.” According to Bresee, “Most cases are occurring in children who are exhibiting pigs, or helping to exhibit pigs and have occurred after a lot of very close contact with pigs over a relatively long period of time.” Dr. Bresee is Chief of the Epidemiology and Prevention Branch in CDC’s Influenza Division.
The 52 new cases reported this week are from the states of Illinois (1), Maryland (12), Michigan (4), Minnesota (1), Ohio (26), Pennsylvania (2), and Wisconsin (6). This is the first report of H3N2v with the pandemic M gene from Maryland and Minnesota. The 6 cases in Maryland
are reported to have had contact with pigs prior to their illness. The one case in Minnesota
The three instances of likely person-to-person spread of H3N2v were recently identified during investigations of cases and their household contacts and are not epidemiologically linked to one another. In all three cases, transmission is thought to have occurred from one person to another person without further spread to additional people. Each of these three instances of likely person-to-person spread happened between 2 people living in the same household, with the initial infection in each household being associated with pig exposure at an agricultural fair.
“We’re not particularly surprised to see what looks like limited human-to-human transmission,” says Bresee. Limited human-to-human spread has been seen in the past, both with this variant virus as well as other variant viruses. “It’s clear though,” Bresee adds, “that this virus is much better able to spread to people. It’s reassuring that we are seeing most cases in people with prolonged contact with pigs and that we are not seeing any sustained community transmission, but this situation definitely warrants our close attention,” says Bresee.
CDC is monitoring for changes in the virus and potential person-to-person transmission of H3N2v. This week CDC updated its guidance to states for enhanced surveillance for influenza-like-illness (ILI) in all people, including people reporting pig exposure. So far, genetic analysis of the viruses submitted to CDC show that all viruses are nearly identical, and very similar to the H3N2v viruses found in 2011.
Illness associated with this virus so far continues to be mostly mild with symptoms similar to seasonal flu. Like seasonal flu, however, serious illness with H3N2v infection is possible. To date, 13 hospitalizations have occurred, but all patients have recovered. Last week CDC issued information for clinicians on H3N2v; guidance which underscores the importance of rapid antiviral treatment of H3N2v virus infections in high risk patients.
The CDC makes the following recommendations to limit the risks of infection from the H3N2v virus.
Preventive Actions
CDC Recommendations For People At High Risk:
- If you are at high risk of serious flu complications and are going to a fair where pigs will be present, avoid pigs and swine barns at the fair this year. This includes children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).
If you are not at high risk, take these precautions:
- Don’t take food or drink or eat, drink or put anything in your mouth in pig areas.
- Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
- Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.
- Avoid close contact with pigs that look or act ill.
- Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes minimizing contact with pigs and wearing personal protective equipment like protective clothing, gloves and masks that cover your mouth and nose when contact is required.
- To further reduce the risk of infection, minimize contact with pigs and swine barns.
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