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Influenza Other Respir Viruses. 2018 May;12(3):360-373. doi: 10.1111/irv.12529. Epub 2018 Feb 1.

The effects of the attributable fraction and the duration of symptoms on burden estimates of influenza-associated respiratory illnesses in a high HIV prevalence setting, South Africa, 2013-2015.

Author information

1
Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.
2
Influenza Program, Centers for Disease Control and Prevention, Pretoria, South Africa.
3
Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.
4
School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
5
Global Immunization Monitoring and Surveillance Team, Expanded Programme on Immunization, Department of Immunization, Vaccines and Biological, World Health Organization, Geneva, Switzerland.
6
Centre for Viral Zoonoses, Department of Medical Virology, University of Pretoria, Pretoria, South Africa.
7
Tshwane Academic Division, National Health Laboratory Service, Pretoria, South Africa.
8
School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
9
Department of Medicine, Pietermaritzburg Metropolitan Hospital, Pietermaritzburg, South Africa.
10
Department of Medicine, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
11
Department of Medicine, Klerksdorp-Tshepong Hospital Complex, Klerksdorp, South Africa.
12
Department of Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
13
Perinatal HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa.
14
Medical Research Council, Respiratory and Meningeal Pathogens Research Unit, University of the Witwatersrand, Johannesburg, South Africa.
15
Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa.

Abstract

BACKGROUND:

The attributable fraction of influenza virus detection to illness (INF-AF) and the duration of symptoms as a surveillance inclusion criterion could potentially have substantial effects on influenza disease burden estimates.

METHODS:

We estimated rates of influenza-associated influenza-like illness (ILI) and severe acute (SARI-10) or chronic (SCRI-10) respiratory illness (using a symptom duration cutoff of ≤10 days) among HIV-infected and HIV-uninfected patients attending 3 hospitals and 2 affiliated clinics in South Africa during 2013-2015. We calculated the unadjusted and INF-AF-adjusted rates and relative risk (RR) due to HIV infection. Rates were expressed per 100 000 population.

RESULTS:

The estimated mean annual unadjusted rates of influenza-associated illness were 1467.7, 50.3, and 27.4 among patients with ILI, SARI-10, and SCRI-10, respectively. After adjusting for the INF-AF, the percent reduction in the estimated rates was 8.9% (rate: 1336.9), 11.0% (rate: 44.8), and 16.3% (rate: 22.9) among patients with ILI, SARI-10, and SCRI-10, respectively. HIV-infected compared to HIV-uninfected individuals experienced a 2.3 (95% CI: 2.2-2.4)-, 9.7 (95% CI: 8.0-11.8)-, and 10.0 (95% CI: 7.9-12.7)-fold increased risk of influenza-associated illness among patients with ILI, SARI-10, and SCRI-10, respectively. Overall 34% of the estimated influenza-associated hospitalizations had symptom duration of >10 days; 8% and 44% among individuals aged <5 and ≥5 years, respectively.

CONCLUSION:

The marginal differences between unadjusted and INF-AF-adjusted rates are unlikely to affect policies on prioritization of interventions. HIV-infected individuals experienced an increased risk of influenza-associated illness and may benefit more from annual influenza immunization. The use of a symptom duration cutoff of ≤10 days may underestimate influenza-associated disease burden, especially in older individuals.

KEYWORDS:

HIV ; South Africa; attributable fraction; influenza; influenza-like illness; rates; severe respiratory illness; symptom duration

PMID:
29210203
PMCID:
PMC5907815
DOI:
10.1111/irv.12529
[Indexed for MEDLINE]
Free PMC Article

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