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J Clin Virol. 2015 Dec;73:108-111. doi: 10.1016/j.jcv.2015.11.008. Epub 2015 Nov 5.

Natural co-infection of influenza A/H3N2 and A/H1N1pdm09 viruses resulting in a reassortant A/H3N2 virus.

Author information

1
Institut Pasteur in Cambodia, Institut Pasteur International Network, Phnom Penh, Cambodia.
2
National Institute of Public Health, Phnom Penh, Cambodia.
3
National Institute of Public Health, Phnom Penh, Cambodia; Centers for Disease Control and Prevention, Cambodia Office, Phnom Penh, Cambodia.
4
Communicable Disease Department, Ministry of Health, Phnom Penh, Cambodia.
5
Institut Pasteur in Cambodia, Institut Pasteur International Network, Phnom Penh, Cambodia. Electronic address: phorwood@pasteur-kh.org.

Abstract

BACKGROUND:

Despite annual co-circulation of different subtypes of seasonal influenza, co-infections between different viruses are rarely detected. These co-infections can result in the emergence of reassortant progeny.

STUDY DESIGN:

We document the detection of an influenza co-infection, between influenza A/H3N2 with A/H1N1pdm09 viruses, which occurred in a 3 year old male in Cambodia during April 2014. Both viruses were detected in the patient at relatively high viral loads (as determined by real-time RT-PCR CT values), which is unusual for influenza co-infections. As reassortment can occur between co-infected influenza A strains we isolated plaque purified clonal viral populations from the clinical material of the patient infected with A/H3N2 and A/H1N1pdm09.

RESULTS:

Complete genome sequences were completed for 7 clonal viruses to determine if any reassorted viruses were generated during the influenza virus co-infection. Although most of the viral sequences were consistent with wild-type A/H3N2 or A/H1N1pdm09, one reassortant A/H3N2 virus was isolated which contained an A/H1N1pdm09 NS1 gene fragment. The reassortant virus was viable and able to infect cells, as judged by successful passage in MDCK cells, achieving a TCID50 of 10(4)/ml at passage number two. There is no evidence that the reassortant virus was transmitted further. The co-infection occurred during a period when co-circulation of A/H3N2 and A/H1N1pdm09 was detected in Cambodia.

CONCLUSIONS:

It is unclear how often influenza co-infections occur, but laboratories should consider influenza co-infections during routine surveillance activities.

KEYWORDS:

A/H1N1pdm09; A/H3N2; Co-infection; Influenza; Reassortant; Reassortment; Seasonal

PMID:
26590689
PMCID:
PMC4674902
DOI:
10.1016/j.jcv.2015.11.008
[Indexed for MEDLINE]
Free PMC Article

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