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Published Date: 2012-08-05 03:52:58
Subject: PRO/AH/EDR> Influenza (64): USA, A/(H3N2)v, CDC report
Archive Number: 20120805.1228593

INFLUENZA (64): USA, A/(H3N2)V, CDC REPORT
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A ProMED-mail post
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International Society for Infectious Diseases
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Date: Fri 3 Aug 2012
Source: Seasonal Influenza (Flu) ,CDC
http://www.cdc.gov/flu/spotlights/h3n2v_us_cases.htm

CDC Reports Cases 18-29 of H3N2v Virus Infection; Continues to Recommend Interim Precautions When Interacting with Pigs
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This week CDC [US Centers for Disease Control and Prevention] reports 12 additional human infections with influenza A (H3N2) variant virus in 3 states: Hawaii (1 case), Ohio (10 cases) and Indiana (1 case). The H3N2v virus contains the M gene from the human influenza A(H1N1)pdm09 (2009 H1N1) virus, as have the previous 17 cases detected since July 2011 [last year]. All of this week's reported cases occurred in people who had direct or indirect contact with swine prior to their illness. The 10 cases in Ohio were associated with attendance at a fair where reportedly ill swine were present. The H3N2v case reported by Indiana also occurred in a person who attended a fair where swine were present. CDC continues to recommend preventive actions people can take to make their fair experience a safe and healthy one.

The number of cases of infection with H3N2v viruses with the M gene from the 2009 H1N1 virus detected in the United States since July 2011 now totals 29 [Hawaii (1), Indiana (7), Iowa (3), Ohio (10), Maine (2), Pennsylvania (3), Utah (1), and West Virginia (2)]. Twenty-three of these cases reported swine contact prior to illness onset. Among those 29 cases, 19 cases were associated with fairs where swine were present. Most human illness with H3N2v virus infection has resulted in signs and symptoms of influenza (fever, cough, runny nose, sore throat, muscle aches); 3 hospitalizations have occurred. All of the people hospitalized had high risk conditions. All H3N2v virus cases have recovered fully.

According to USDA [US Department of Agriculture] swine influenza surveillance, this swine H3N2 virus with the pandemic [virus] M gene has been detected in swine in a number of U.S. states. This virus may be circulating widely in U.S. swine at this time. It should be noted, however, that influenza viruses have not been shown to be transmissible to people through eating properly handled and prepared pork (pig meat) or other products derived from pigs. It is possible that acquisition of the M gene from the 2009 H1N1 virus may allow H3N2v viruses to be more transmissible from pigs to people and from person-to-person.

Late summer is typically fair season across the United States, and fairs are a setting that can provide many opportunities for exposures to occur between pigs and people. CDC continues to advise people to take recommended precautions when interacting with pigs or their environments, including frequent hand washing and avoiding contact with pigs that appear ill. The National Association of State Public Health Veterinarians has developed the "Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2011" to provide some preventive actions that are applicable to people raising swine, showing swine at fairs, or attending fairs.

This includes:
- Wash your hands frequently with soap and running water before and after exposure to animals.
- Never eat, drink or put things in your mouth while in animal areas and don't take food or drink into animal areas.
- Young children, pregnant women, people 65 and older and people with weakened immune systems should be extra careful around animals.
- If you have animals -- including swine -- watch them for signs of illness and call a veterinarian if you suspect they might be sick.
- Avoid close contact with animals that look or act ill, when possible.
- Avoid contact with pigs if you are experiencing flu-like symptoms.
- If you must come in contact with pigs while you are sick, or if you must come in contact with pigs known or suspected to be infected, or their environment, you should use appropriate protective measures (for example, wear protective clothing, gloves, masks that cover your mouth and nose, and other personal protective equipment) and practice good respiratory and hand hygiene.

Additionally, in response to recent human cases of H3N2v virus infection, CDC would like to convey the following information:

1. Children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic medical conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions) are at high risk from serious complications if they get influenza. These people should consider avoiding exposure to pigs and swine barns this summer, especially if sick pigs have been identified.

2. Studies conducted by CDC have indicated that children younger than 10 years old would have little to no immunity against H3N2v virus, whereas adults may have some cross-protective immunity. Most cases of H3N2v have occurred in children at this time.

3. There are two FDA-approved drugs that are expected to be effective in treating illness associated with H3N2v virus infection. The antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) - which are used to treat infection with human seasonal influenza viruses -- are also expected to be effective in treating H3N2v virus. Antiviral treatment is most effective when started as soon as possible after illness onset.

4. Signs and symptoms of H3N2v virus infection cannot be differentiated from those caused by other respiratory infections, including seasonal influenza virus infection.

5. Rapid influenza diagnostic tests may not detect H3N2v virus in human respiratory specimens ([they may give] false negative results). If H3N2v virus infection is suspected because of recent exposure to pigs or to an ill person who had contact with pigs, testing of respiratory specimens should be done at a state health department.

6. Influenza viruses have not been shown to be transmissible to people through eating properly handled and prepared pork (pig meat) or other products derived from pigs.

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Communicated by:
ProMED-mail Rapporteur Kunihiko Iizuka

[While swine influenza A viruses seldom infect humans, such infections have occurred. Human infections with swine viruses are thought to occur in the same way that seasonal influenza viruses spread among people. Pigs that are infected shed influenza virus -- possibly in coughs or sneezes -- and people who are nearby can breathe the virus in. Infection also may occur by a person touching a surface or object that has virus on it and then touching their own mouth or nose."

Signs of swine flu in pigs can include fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed. Some pigs infected with influenza viruses, however, may have no symptoms at all.

More information about H3N2v is available on the CDC website at "Information on H3N2 Variant Influenza A Viruses"
http://www.cdc.gov/flu/swineflu/influenza-variant-viruses-h3n2v.htm.

Influenza A/(H3N2)v viruses have only been detected in North America so far. - Mod.CP]

[In order to improve communications and avoid confusion, FAO, OIE and WHO established, in late 2011, a working group of experts to standardize the terminology for variant influenza viruses. The joint recommendation for the above mentioned A(H3N2) virus was: A (H3N2)v , where "v" stands for "variant". Subclinical or mild cases of influenza have been reportedly observed in swine in contact with infected humans (eg a county fair in Indiana) where the A (H3N2)v strain was identified in both man and animal. These cases are not regarded as the OIE-notifiable "Swine influenza", a highly contagious viral infection of pigs caused by pathogenic Swine Influenza Virus (SIV) strains. In some instances, SIV infections are associated with reproductive disorders such as abortion. Morbidity rates can reach 100% with SIV infections, while mortality rates are generally low. Secondary bacterial infections can exacerbate the clinical signs following infection with SIV. Transmission is through contact with SIV-containing secretions such as nasal discharges and aerosols created by coughing or sneezing.(H3N2)v causing sub-clinical or mild disease in swine, seems not to be regarded as the notifiable SIV. During 2009/2010, when the A(H1N1)pdm09 virus (Pandemic influenza A/H1N1 (2009) virus) was reportedly spreading globally in humans, becoming a cause for international concern, more than 20 countries notified the OIE about the identification of the virus in swine, as an "emerging disease". This virus was generally regarded to spread through the human-to-swine route. - Mod.ARN]

[The Hawaiian case presents a puzzle. In ProMED post Influenza (61): USA (HI) A/(H3N2)v, pig worker, 20120802.1225864, state veterinarian Dr. James Foppoli is quoted as saying "Human-to-human transmission is uncommon, so that's not a likely source. You've got to suspect that there's a pig intermediate somewhere along the line where the person got the virus." Since there is no suggestion that the human had become infected during travel outside Hawaii, is that island importing pigs from the USA mainland? - Mod.JW]

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