Published Date: 2012-09-30 19:22:22
Subject: PRO/AH/EDR> Influenza (95): USA (OH) H3N2v, hospitalizations
Archive Number: 20120930.1316697
INFLUENZA (95): USA (OHIO), H3N2V, HOSPITALIZATIONS
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Fri 28 Sep 2012
Source: Morbidity and Mortality Weekly Report (MMWR) 61(38);764-767 [abridged & edited]
Since July 2012, 305 cases of infection with influenza A (H3N2) variant (H3N2v) virus containing the influenza A (H1N1)pdm09 M gene have occurred in multiple U.S. states, primarily associated with swine exposure at agricultural fairs (1). In Ohio, from 28 Jul to 25 Sep 2012, a total of 106 confirmed H3N2v cases were identified through enhanced surveillance.
Whereas most H3N2v patients experienced mild, self-limited influenza-like illness (ILI), 11 of the Ohio patients were hospitalized, representing 69 percent of all H3N2v hospitalizations in the United States. Of these hospitalized H3N2v patients, 6 were at increased risk for influenza complications because of age or underlying medical conditions, including the only H3N2v-associated fatality reported in the United States to date.
This report summarizes the epidemiology and clinical features of the 11 hospitalized H3N2v patients in Ohio. These findings reinforce the recommendation for persons at high risk for influenza complications to avoid swine exposure at agricultural fairs this fall  (2). In addition, persons not at high risk for influenza complications who wish to reduce their risk for infection with influenza viruses circulating among pigs also should avoid swine and swine barns at agricultural fairs this fall.
[Interested readers should access the original text via the source URL to obtain descriptions of the case finding, case reports, and the original references cited.]
MMWR Editorial Note:
Of the hospitalized H3N2v patients described in this report, 10 of 11 were children, and 6 of 11 were considered at high risk for influenza complications because they were aged under 5 years or had underlying medical conditions. All hospitalizations were brief, and severe illness was observed only in the patient who died. 6 patients reported direct contact with pigs at agricultural fairs. Among 4 patients with indirect swine exposure at fairs, 3 reported 2 or more days of fair attendance. One patient had no reported swine exposure. These findings support current recommendations that persons at high risk for influenza complications, including children aged under 5 years and persons with chronic underlying medical conditions that confer high risk for severe complications from influenza, should avoid the swine barn and pens when attending agricultural fairs (2).
Clinicians should be aware that rapid influenza diagnostic tests might not detect H3N2v virus (4). Specific H3N2v virus testing is available only at state public health laboratories and CDC. In 2 instances, rRT-PCR testing for H3N2v was positive after 10 days or more of illness in patients who were not immunosuppressed and did not receive antiviral treatment. Both patients had documented infection with other pathogens (_P. aeruginosa_ in patient A and parainfluenza virus type 3 in patient B). Although _P. aeruginosa_ bacteremia undoubtedly contributed to patient A's death, the role of parainfluenza virus infection in patient B's illness is unknown.
Of the 6 patients at high risk for influenza complications, 2 received antiviral treatment within 2 days after illness onset, while 5 of 11 patients were not treated at any time during their hospitalization.
***[ProMED emphsis] Clinicians should be aware that starting empiric antiviral treatment for 5 days with oral oseltamivir or inhaled zanamivir as soon as possible after onset of symptoms is recommended for any hospitalized patient with suspected influenza, including H3N2v, without waiting for testing results (2,5). Beginning antiviral treatment as soon as possible also is recommended for outpatients with suspected influenza who are at high risk for influenza complications (2,5).
5 H3N2v patients reported here were not in a high risk group, highlighting the fact that H3N2v virus infection can cause illness resulting in hospitalization, even in otherwise healthy persons. The current interim recommendations from CDC also encourage early antiviral treatment of non-high-risk outpatients with suspected H3N2v virus infection (2).
Public health professionals should be aware of the possibility of continued outbreaks of H3N2v virus related to agricultural fairs where swine are present. Pigs with influenza virus infection might be present at agricultural fairs, and swine might be asymptomatically infected with H3N2 or other influenza A viruses (6,7). Limited serologic studies indicate that children aged under 10 years lack cross-protective antibodies to H3N2v virus (8). Persons, especially young children, might be infected with influenza viruses through direct or indirect swine exposure (9). Recommendations for preventing swine-to-human transmission of influenza viruses among the general population include staying away from pigs that appear ill (e.g. are coughing or sneezing, off feed, or lethargic) and washing hands with soap and water after contact with swine. Persons at high risk for influenza complications because of age (under 5 years or 65 years or older) or underlying medical conditions should avoid swine and swine barns at agricultural fairs this fall . Persons not at high risk for influenza complications who wish to reduce their risk for infection with influenza viruses circulating among pigs also should avoid swine and swine barns at fairs this fall.
Continued close communication and collaboration between human and animal health agencies for ongoing surveillance and investigation of influenza viruses among pigs and humans are needed to help guide and potentially expand measures to reduce the public health risk of H3N2v and related viruses.
ProMED-mail Rapporteur Kunihiko Iizuka
[Beginning in the summer of 2012, CDC reported increases in numbers of cases of human infection with influenza A (H3N2) variant (H3N2v) viruses associated with swine exposure at agricultural fairs. Nationwide, 305 cases, 16 hospitalizations, and one death across 10 states have been reported since July 2012.
Of 16 patients hospitalized with confirmed H3N2v virus infection, 11 were Ohio residents, including the only H3N2v-associated fatality to date. All but one of the Ohio patients were children, and 6 were considered high-risk for complications of influenza because they were aged under 5 years or had underlying medical conditions; 4 high-risk persons became ill after indirect contact with pigs. These findings support current CDC recommendations that persons at high risk for complications of influenza should avoid exposure to swine at agricultural fairs this fall .
County and state fairs in the United States continue to occur through the month of October, highlighting the potential for continued cases of H3N2v virus infection. Persons at high risk for complications of influenza should avoid exposure to swine at agricultural fairs. - Mod.CP
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