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PLoS One. 2017 May 25;12(5):e0177655. doi: 10.1371/journal.pone.0177655. eCollection 2017.
Epidemiology of influenza B/Yamagata and B/Victoria lineages in South Africa, 2005-2014.
Seleka M1, Treurnicht FK1, Tempia S1,2,3, Hellferscee O1,4, Mtshali S5, Cohen AL6, Buys A1, McAnerney JM1, Besselaar TG6, Pretorius M1, von Gottberg A1,4, Walaza S1,7, Cohen C1,8, Madhi SA1,7,9, Venter M10.
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Abstract
BACKGROUND:
Studies describing the epidemiology of influenza B lineages in South Africa are lacking.
METHODS:
We conducted a prospective study to describe the circulation of influenza B/Victoria and B/Yamagata lineages among patients of all ages enrolled in South Africa through three respiratory illness surveillance systems between 2005 and 2014: (i) the Viral Watch (VW) program enrolled outpatients with influenza-like illness (ILI) from private healthcare facilities during 2005-2014; (ii) the influenza-like illnesses program enrolled outpatients in public healthcare clinics (ILI/PHC) during 2012-2014; and (iii) the severe acute respiratory illnesses (SARI) program enrolled inpatients from public hospitals during 2009-2014. Influenza B viruses were detected by virus isolation during 2005 to 2009 and by real-time reverse transcription polymerase chain reaction from 2009-2014. Clinical and epidemiological characteristics of patients hospitalized with SARI and infected with different influenza B lineages were also compared using unconditional logistic regression.
RESULTS:
Influenza viruses were detected in 22% (8,706/39,804) of specimens from patients with ILI or SARI during 2005-2014, of which 24% (2,087) were positive for influenza B. Influenza B viruses predominated in all three surveillance systems in 2010. B/Victoria predominated prior to 2011 (except 2008) whereas B/Yamagata predominated thereafter (except 2012). B lineages co-circulated in all seasons, except in 2013 and 2014 for SARI and ILI/PHC surveillance. Among influenza B-positive SARI cases, the detection of influenza B/Yamagata compared to influenza B/Victoria was significantly higher in individuals aged 45-64 years (adjusted odds ratio [aOR]: 4.2; 95% confidence interval [CI]: 1.1-16.5) and ≥65 years (aOR: 12.2; 95% CI: 2.3-64.4) compared to children aged 0-4 years, but was significantly lower in HIV-infected patients (aOR: 0.4; 95% CI: 0.2-0.9).
CONCLUSION:
B lineages co-circulated in most seasons except in 2013 and 2014. Hospitalized SARI cases display differential susceptibility for the two influenza B lineages, with B/Victoria being more prevalent among children and HIV-infected persons.
PMID: 28542324 DOI: 10.1371/journal.pone.0177655
Epidemiology of influenza B/Yamagata and B/Victoria lineages in South Africa, 2005-2014.
Seleka M1, Treurnicht FK1, Tempia S1,2,3, Hellferscee O1,4, Mtshali S5, Cohen AL6, Buys A1, McAnerney JM1, Besselaar TG6, Pretorius M1, von Gottberg A1,4, Walaza S1,7, Cohen C1,8, Madhi SA1,7,9, Venter M10.
Author information
Abstract
BACKGROUND:
Studies describing the epidemiology of influenza B lineages in South Africa are lacking.
METHODS:
We conducted a prospective study to describe the circulation of influenza B/Victoria and B/Yamagata lineages among patients of all ages enrolled in South Africa through three respiratory illness surveillance systems between 2005 and 2014: (i) the Viral Watch (VW) program enrolled outpatients with influenza-like illness (ILI) from private healthcare facilities during 2005-2014; (ii) the influenza-like illnesses program enrolled outpatients in public healthcare clinics (ILI/PHC) during 2012-2014; and (iii) the severe acute respiratory illnesses (SARI) program enrolled inpatients from public hospitals during 2009-2014. Influenza B viruses were detected by virus isolation during 2005 to 2009 and by real-time reverse transcription polymerase chain reaction from 2009-2014. Clinical and epidemiological characteristics of patients hospitalized with SARI and infected with different influenza B lineages were also compared using unconditional logistic regression.
RESULTS:
Influenza viruses were detected in 22% (8,706/39,804) of specimens from patients with ILI or SARI during 2005-2014, of which 24% (2,087) were positive for influenza B. Influenza B viruses predominated in all three surveillance systems in 2010. B/Victoria predominated prior to 2011 (except 2008) whereas B/Yamagata predominated thereafter (except 2012). B lineages co-circulated in all seasons, except in 2013 and 2014 for SARI and ILI/PHC surveillance. Among influenza B-positive SARI cases, the detection of influenza B/Yamagata compared to influenza B/Victoria was significantly higher in individuals aged 45-64 years (adjusted odds ratio [aOR]: 4.2; 95% confidence interval [CI]: 1.1-16.5) and ≥65 years (aOR: 12.2; 95% CI: 2.3-64.4) compared to children aged 0-4 years, but was significantly lower in HIV-infected patients (aOR: 0.4; 95% CI: 0.2-0.9).
CONCLUSION:
B lineages co-circulated in most seasons except in 2013 and 2014. Hospitalized SARI cases display differential susceptibility for the two influenza B lineages, with B/Victoria being more prevalent among children and HIV-infected persons.
PMID: 28542324 DOI: 10.1371/journal.pone.0177655