Variant H3N2 Spreads to Three More States

August 22, 2012 — 

Maryland, Pennsylvania, and Wisconsin have confirmed their 1st novel H3N2 (H3N2v) cases linked to contact with pigs, especially at fairs, this summer [2012], as the national total has grown to 230 cases across 9 states, according to state reports and the US Centers for Disease Control and Prevention (CDC). Indiana reported the highest number of cases at 138, up from 120 reported the previous week. The swine-origin H3N2 virus contains the matrix gene from the 2009 H1N1 virus and so far this summer has been detected in Hawaii, Illinois, Indiana, Maryland, Michigan, Ohio, Pennsylvania, West Virginia, and Wisconsin.

Maryland today [17 Aug 2012] reported its 1st 6 H3N2v infections, in 5 children and one adult from Queen Anne's county who had direct contact with pigs. None of the patients had serious infections or were hospitalized. Also, testing by the Maryland Department of Agriculture has detected a similar virus in pigs that the sick people had contact with at 4 Queen Anne's county farms. The Maryland Department of Health and Mental Hygiene (MDHMH) said in a statement that the findings in pigs are preliminary and will be confirmed by more testing. It said animal health officials will boost surveillance for the virus and monitor pigs at agricultural fairs in Maryland more closely for flulike symptoms. Fairs are under way in Montgomery and Worcester counties.

Pennsylvania is reporting 4 confirmed and 6 probable cases, all youth who participated in the Huntingdon County Fair that took place from 5 through 11 Aug [2012], according to a statement today [17 Aug 2012] from the Pennsylvania Department of Health (PDH). None of the patients were hospitalized, and though investigations are ongoing, so far authorities have found no evidence of person-to-person spread. Eli Avila, MD, JD, MPH, Pennsylvania's secretary for health, said the illnesses fit the typical flu profile, and he urged people to take the same precautions as for seasonal flu. "People should use common sense and take steps to protect their health if they're visiting or exhibiting in a county fair in the coming weeks, especially if they are at high risk for illnesses," he added.

Wisconsin health officials today [17 Aug 2012] said the Wisconsin State Laboratory of Hygiene has confirmed 2 H3N2v cases, both with links to the Wisconsin State Fair, according to a statement from the Wisconsin Department of Health Services (WDHS). The Wisconsin State Fair took place from 1 through 11 Aug 2012 in West Allis, a suburb of Milwaukee. One case was in an adult from southeastern Wisconsin who worked at the fair, but did not have direct contact with pigs. The other was in an adolescent from the western part of the state who exhibited swine at the fair. Neither patient has been hospitalized and both are recovering from their illness, the WDHS said. The Wisconsin Division of Public Health is working with the state lab and local health departments to identify additional cases. Henry Anderson, MD, Wisconsin's state health officer, said in the statement, "We encourage people to enjoy all their local fairs have to offer this summer, but take precautions to reduce the chances of getting H3N2v influenza." He urged older people, pregnant women, young children, and people with weakened immune systems to avoid swine barns this season.

Meanwhile, Indiana reported that 3 more counties (Marion, Marshall, and Delaware) are reporting H3N2v cases, pushing the total number of affected counties to 23. In a statement yesterday [16 Aug 2012], the Indiana State Department of Health (ISDH) said it found some duplicated samples that were submitted to the state lab and it has adjusted the number of confirmed cases in some counties. Indiana health officials continue to investigate the cases but so far have found no evidence of person-to-person transmission, according to the statement, which said human infections are most likely in people who have close proximity to infected pigs, such as working with them in barns and in livestock exhibits at fairs.

Joe Bresee, MD, medical epidemiologist in the CDC's Influenza Division, told CIDRAP News that most of the H3N2v cases are still occurring in kids and people who have direct exposure to pigs, such as spending all day in a barn with them at a fair. "There have been some casual exposure cases, but not many," he said, adding that the CDC doesn't have enough information about all of the cases yet to assess the relative risks of different types of exposure. The CDC expects to get more system data from the H3N2v infections in the next few weeks, Bresee said, but so far, more than 90 percent of the infections are occurring in kids, the same level the CDC reported last week.

The European Centre for Disease Prevention and Control said no swine H3N2 virus that contain the former pandemic virus's matrix gene have been detected in European pigs. Elsewhere, Hong Kong's Center for Health Protection (CHP) announced today [17 Aug 2012] that variant H3N2 has been declared a notifiable disease. A spokesman for the CHP said in a statement that the move was made to prepare for the possible importation of the virus into Hong Kong and that the strengthened surveillance can help streamline prevention and control measures.

[Editor's note: Official outbreak information is updated every Friday on the CDC website. Additional influenza information for swine producers and veterinarians is available on the Pork.org website.]

Source: Center for Infectious Disease Research & Policy (CIDRAP) News [edited] By: Lisa Schnirring