Reassortant H3N2 virus detected in Pennsylvania & Indiana – Source CDC
# 5913
My thanks to Giuseppe Michieli and Missouri Watcher on FluTrackers for the links to the State of Maine HAN Advisory (2011PHADV018), and weekly influenza surveillance report describing the recent detection of a novel Swine Origin Influenza Virus (SOIV) in that state.
This is the fifth such virus detection from across the country over the past 3 months, with 3 previous cases reported in Pennsylvania and 1 in Indiana (see CDC Update On Recent Novel Swine Flu Cases).
In all 5 of these cases, the virus has been a swine H3N2 virus with the M segment gene borrowed from the 2009 H1N1 virus.
From the Weekly Flu Surveillance report:
• HETL detected a case of influenza A virus that was inconclusive during subtyping. On October 17
Federal CDC confirmed this isolate to be the 5th recognized case of human infection with S-OtrH3N2
with the M segment gene from the pH1N1virus (also identified in one case in Indiana and three cases in
Pennsylvania). Investigation is ongoing.More information can be found in a Health Alert, released 10/19/2011 accessible through: http://www.maine.gov/tools/whatsnew/attach.php?id=313425&an=1.
The MAINE HAN Message provides the following details:
(EXCERPT)
This child became ill in early October 2011 with symptoms similar to seasonal influenza including fever,
cough, headache, sore throat and myalgia. Prior to illness, the child had exposure to swine including time
spent in a closed setting at an agricultural fair. Maine CDC and the Department of Agriculture are currently investigating exposures. Presently this is an isolated event and Maine CDC has not confirmed any person to person transmission.
Recommendations: Maine CDC recommends the following for healthcare providers:
• Maintain a heightened awareness for influenza-like illness (ILI) defined as fever greater than 100° with cough or sore throat, in the absence of another known cause.
- Consider influenza testing by PCR for:
patients with ILI with recent exposure to pigs.- patients with ILI who are hospitalized,
- patients with ILI who have died,
- patients where a diagnosis of influenza would affect clinical care, infection control, or
management of contacts.• Consider use of antivirals to quickly limit potential human transmission
• Vaccinate patients and healthcare workers as a primary strategy to prevent influenza
As I wrote last month in What Lies Beneath, it appears that very limited human-to-human transmission of this virus may have occurred, but the virus does not yet appear capable of sustained and efficient human transmission.
The concern, of course, is that could eventually change. Hence the ongoing epidemiological investigation.
Below you’ll find excerpts from the CDC’s SOIV page regarding these cases (reformatted for readability).
Reported Human Infections with Swine-Origin Influenza Viruses (SOIV) in the United States since 2005
As of September 9, 2011, 25 cases of human infection with swine origin influenza viruses have been reported in the United States. These are viruses that normally infect pigs. Like human influenza viruses, there are different subtypes and strains of swine-origin influenza viruses.
The main swine influenza viruses circulating in U.S. pigs in recent years are swine triple reassortant (tr) H1N1 influenza virus, trH3N2 virus and trH1N2 virus. Of the 25 human cases reported since 2005, 12 have been trH1N1 viruses, 12 have been trH3N2 viruses and one has been a trH1N2 virus.
All 25 persons infected with swine viruses recovered from their illness. Eighteen cases occurred in children (persons 18 or younger) and 7 cases occurred in adults. In 21 cases, direct or indirect exposure to swine prior to onset of illness has been identified.
Likely transmission of swine-origin influenza virus from close contact with an infected person has been observed in investigations of human infections with swine-origin influenza A virus, but has not resulted in sustained human-to-human transmission.
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