Transcript: CDC Telebriefing: Influenza A (H3N2) Variant Virus
August 3, 2012

Extract
“…This is Joe Bresee at the flu division at CDC. Today I’m going to give you a quick update on an increase in the number of cases of influenza A H3N2 variant virus because on August 3rd, today, CDC’s FluView U.S. weekly influenza surveillance report, announced 12 new cases of H3N2 variant virus infection from three different states: Hawaii, Indiana and Ohio.  The virus was first detected in humans late last summer, July of 2011 and since July 12th, 2011, there have been 29 total cases of H3N2 variant virus infection detected, including the 16 cases occurring in the last three weeks.  Twenty-nine cases of infection with this H3N2 virus since the fall of 2011 is a significant increase in the number of detections for these types of virus we’ve seen in recent years.  All 29 cases were infected with H3N2v viruses that contain the matrix or M gene from the influenza A H1 pandemic virus.  This M gene may confirm increased transmissibility to and among humans compared with other variant influenza viruses…

“…So a summary of the recent cases.  Each of the recent 16 H3N2 variant cases reported in the last few weeks reported contact with swine prior to their illness onset.  In 15 of these cases contact occurred while attending or exhibiting swine at agricultural fairs.  All cases have been laboratory confirmed at CDC.  While no human-to-human spread has been identified in recent cases, limited transmission from person to person is thought to have occurred on three occasions in the fall and winter of 2011.  Importantly, sustained efficient community transmission of this virus, H3N2v virus has not been detected to date.  Clinical symptoms of the H3N2 virus infections have been generally consistent with symptoms associated with seasonal influenza virus, such as fever, cough, sore throat, muscle aches and headache.  No hospitalizations or deaths have occurred from the 16 confirmed cases but three cases were hospitalized among those detected last year in 2011.  All of those hospitalizations occurred among people with underlying diseases that put them at high risk for severe influenza infection.  Of the 16 recent cases, 13 of the cases are among children and three are among adults.  This is similar to the ages of the cases in 2011 and early 2012 that comprise the whole 29 and it actually is consistent with data from research studies that indicate that children may be more susceptible to the infection than adults…

“…CDC, along with state and local health departments and our colleagues in animal health will continue to monitor for these cases and provide information on how to prevent them.  Because influenza viruses are always evolving, we will watch closely for signs that the virus has gained an increased capacity for efficient and sustained human-to-human transmission.  Thus far we have not seen this type of transmission and therefore are not seeing features consistent with the earlier influenza pandemic.  Even so, the H3N2 variant virus vaccine has been prepared or the candidate has been prepared in clinical trials are being planned for this year.  So in summary, while sporadic cases of this variant virus have been observed for many years — variant viruses have been observed for many years, we’ve detected cases of this variant virus with increasing frequency over the last year, particularly in the last month.  We expect that additional cases of human infection with H3N2v virus will be identified either from contact with infected swine or through subsequent limited human-to-human spread, we also expect that some of the cases might be severe…”