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

Stefano Tempia; Sibongile Walaza; Jocelyn Moyes; Adam L Cohen; Claire von Mollendorf; Meredith L McMorrow; Sarona Mhlanga; Florette K Treurnicht; Marietjie Venter; Marthi Pretorius; Orienka Hellferscee; Nicole Wolter; Anne von Gottberg; Arthemon Nguweneza; Johanna M McAnerney; Halima Dawood; Ebrahim Variava; Shabir A Madhi; Cheryl Cohen

doi:10.1111/irv.12529

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

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

Authors

Stefano Tempia^{1

2

3}, Sibongile Walaza^{3

4}, Jocelyn Moyes^{3

4}, Adam L Cohen^{1

5}, Claire von Mollendorf^{3

4}, Meredith L McMorrow^{1

2}, Sarona Mhlanga³, Florette K Treurnicht³, Marietjie Venter⁶, Marthi Pretorius^{3

6

7}, Orienka Hellferscee^{3

8}, Nicole Wolter^{3

8}, Anne von Gottberg^{3

8}, Arthemon Nguweneza³, Johanna M McAnerney³, Halima Dawood^{9

10}, Ebrahim Variava^{11

12

13}, Shabir A Madhi^{3

14

15}, Cheryl Cohen^{3

4}

Affiliations

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.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

MeSH terms

Adolescent
Adult
Aged
Child
Child, Preschool
Cost of Illness*
Epidemiological Monitoring*
Female
HIV Infections / complications
HIV Infections / epidemiology*
HIV Infections / virology
Humans
Influenza, Human / epidemiology
Influenza, Human / virology
Male
Middle Aged
Nasopharynx / virology
Orthomyxoviridae / isolation & purification
Prevalence
Prospective Studies
Respiratory Tract Infections / epidemiology*
Respiratory Tract Infections / virology
South Africa / epidemiology
Young Adult

Abstract

Publication types

MeSH terms

Grants and funding