267956 Repeat infections with 2009 A/H1N1 influenza during three inflenza seasons, 2008/09 to 2010/11

Sunday, October 28, 2012

Owen Simwale , Infectious Disease Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Stephen Ostroff, MD , Bureau of Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Michael Allen, MPH , Infectious Disease Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Background There is limited literature on the occurrence of influenza repeat infections re-infection with the same subtype of influenza within a period of 12 months. Objectives We examined the occurrence of influenza A/H1N1 re-infections among rt-PCR positive cases reported to the Pennsylvania Department of Health (PA DOH) during three influenza seasons, 2008/09 to 2010/11.

Methods All lab positive influenza cases reported to the PA DOH between October 1, 2008 to October 2011 were examined for repeat infections. Only r-PCR based tests were included in the final analysis.

Results A total of 103, 210 lab positive flu cases were reported during the study period. Of these, 128 (0.1%) individuals tested positive for influenza on two different occasions within a 12 month period. A majority (102, 80%)) of these individuals tested positive for influenza B followed by influenza type A. The majority of second infections occurred within 8 months (median 236 days, range 103 to 346). Twenty six (26) individuals tested positive for the same type of influenza twice. However, only 4 of these were confirmed by rt-PCR and they all involved 2009A/H1N1. A majority (115/87%) of repeat infections involved children <20 years old. None of these subsequent infections resulted in death or hospitalizations.

Conclusions Although rarely documented in our statewide surveillance, a small number of repeat influenza infections were identified. Most were caused by different influenza types, and occurred predominantly in children and teenagers.

Learning Areas:
Biostatistics, economics
Conduct evaluation related to programs, research, and other areas of practice
Provision of health care to the public
Public health or related public policy
Public health or related research

Learning Objectives:
1. Discuss rare situations where an individual is re-infected with influenza viruses within a 12 months period. 2. Discuss how surveillance data may be used to track influenza re-infections

Keywords: Infectious Diseases, Surveillance

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I work on influenza surveillance at the Pennsylvania Department of Health
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.