Today has been a busy day at the CDC as they addressed the recent spike in swine H3N2v flu infections across the heartland. There have been 16 human cases identified over the past 3 weeks, and of those, 12 are from this week.
Earlier today we saw an update (see The CDC On Recent H3N2v Cases) giving the current case counts, and background information. At 12pm EDT today, the CDC held a teleconference for the media.
While providing no major revelations beyond what had already been reported the past couple of days, today’s conference does provide clarity on some of details of these novel outbreaks, and a good feel for how the CDC is approaching the situation.
Fair warning, the audio link has 20 minutes of canned music before the conference begins.
CDC Telebriefing: Influenza A (H3N2) Variant Virus
Friday, August 3, 2012, Noon ET
- Audio recording (MP3, 12.3MB)
The CDC also published a HAN (Health Alert Network) advisory today on the H3N2v. These HAN releases are designed to ensure that communities, agencies, health care professionals, and the general public are able to receive timely information on important public health issues.
There are 4 types of HAN releases.
Conveys the highest level of importance; warrants immediate action or attention.
Provides important information for a specific incident or situation; may not require immediate action.
Provides updated information regarding an incident or situation; unlikely to require immediate action.
Provides general information that is not necessarily considered to be of an emergent nature.
Today’s HAN Message is an ADVISORY.
This is an official
CDC HEALTH ADVISORY
Distributed via the HAN Info Service
August 3, 2012, 11:00 EST
Summary and Background
Multiple infections with variant* influenza A (H3N2v) viruses have been identified in 3 states in recent weeks. From July 12 through August 3, 2012, 16 cases of H3N2v were reported and confirmed by CDC. This virus was first detected in humans in July 2011. It has also been isolated in U.S. swine in many U.S. states. Since July 12, 2011, there have been 29 cases of H3N2v virus infection, including the 16 cases occurring in the last three weeks. All 29 cases were infected with H3N2v viruses that contain the matrix (M) gene from the influenza A (H1N1)pdm09 virus. This M gene may confer increased transmissibility to and among humans, compared to other variant influenza viruses. All cases have been laboratory-confirmed at CDC. Each of the 16 cases identified since July 12, 2012, reported contact with swine prior to illness onset; in 15 cases, contact occurred while attending or exhibiting swine at an agricultural fair. While the viruses identified in these cases are genetically nearly identical, separate swine exposure events in each state were associated with human infections. There is no indication that the cases in different states are epidemiologically related.
Clinical characteristics of the 16 H3N2v recent cases have been generally consistent with signs and symptoms of seasonal influenza, and have included fever, cough, pharyngitis, myalgia, and headache. No hospitalizations or deaths have occurred among the 16 confirmed cases since July 2012. 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.
Novel influenza A virus infection has been a nationally notifiable condition in the United States since 2007. Since that time, human infection with animal-origin influenza viruses has been rare, with ≤6 cases reported each year, until 2011 when 14 cases were identified. While most of the cases are thought to have been infected as a result of close contact with swine, limited human-to-human transmission of this virus was identified in some cases in 2011. Therefore, enhanced influenza surveillance is indicated, especially in regions and states with confirmed H3N2v cases.
The bottom line right now is that the CDC is obviously concerned over the increase in H3N2v infections being reported, but is not particularly alarmed.
The virus does not yet appear capable of efficient and sustained transmission among people, and until that happens, poses only a relatively minor public health threat.
The rub is, the virus could acquire that ability at any time. It could happen tomorrow, or it might not happen for years.
Or perhaps, not at all.
For now the risks are primarily to those who come in contact with pigs, so the CDC is offering advice to fair goers, and those who raise swine, on how to best reduce the risk of infection.
More cases are likely to be announced over the next few weeks as the epidemiological investigation continues, but we’ll simply have to wait and see if this virus manages to adapt well enough to human physiology to present a significant public health threat.
For some of my earlier posts on this week’s surge in H3N2v cases, you may wish to revisit: