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Volume 23, Number 7—July 2017
Research

Attributable Fraction of Influenza Virus Detection to Mild and Severe Respiratory Illnesses in HIV-Infected and HIV-Uninfected Patients, South Africa, 2012–2016

Stefano TempiaComments to Author , Sibongile Walaza, Jocelyn Moyes, Adam L. Cohen, Claire von Mollendorf, Meredith L. McMorrow, Florette K. Treurnicht, Marietjie Venter, Marthi Pretorius, Orienka Hellferscee, Nicole Wolter, Anne von Gottberg, Athermon Nguweneza, Johanna M. McAnerney, Halima Dawood, Ebrahim Variava, Shabir A. Madhi, and Cheryl CohenComments to Author 
Author affiliations: National Health Laboratory Service, Johannesburg, South Africa (S. Tempia, S. Walaza, J. Moyes, C. von Mollendorf, F.K. Treurnicht, M. Pretorius, O. Hellferscee, N. Wolter, A. von Gottberg, A. Nguweneza, J.M. McAnerney, S.A. Madhi, C. Cohen); US Centers for Disease Control and Prevention, Atlanta, Georgia, USA (S. Tempia, A.L. Cohen, M.L. McMorrow); US Centers for Disease Control and Prevention, Pretoria, South Africa (S. Tempia, A.L. Cohen, M.L. McMorrow); University of the Witwatersrand, Johannesburg (S. Walaza, J. Moyes, C. von Mollendorf, O. Hellferscee, N. Wolter, A. von Gottberg, E. Variava, S.A. Madhi, C. Cohen); World Health Organization, Geneva, Switzerland (A.L. Cohen); University of Pretoria, Pretoria (M. Venter, M. Pretorius); Pietermaritzburg Metropolitan Hospital, Pietermaritzburg, South Africa (H. Dawood); University of KwaZulu-Natal, Pietermaritzburg (H. Dawood); Klerksdorp-Tshepong Hospital Complex, Klerksdorp, South Africa (E. Variava)

Main Article

Table 2

AF and AF-adjusted prevalence of influenza viruses among participants in a study of the AF of influenza virus detection to mild and severe respiratory illnesses, Klerksdorp and Pietermaritzburg, South Africa, May 2012–April 2016*

Category
Total

HIV-infected

HIV-uninfected
AF, % (95% CI)
AF-adjusted prev, %
AF, % (95% CI)
AF-adjusted prev, %
AF, % (95% CI)
AF-adjusted prev, %
Outpatients with influenza-like illness
Age, y†
<1 96.8 (85.3–99.3) 7.4 98.4 (83.0–∞)‡ 35.8 94.1 (74.9–98.6) 6.6
1–4 92.8 (82.2–97.0) 14.5 94.6 (72.2–98.9) 19.7 90.3 (77.7–95.8) 14.0
5–24 91.4 (81.3–96.0) 14.8 93.5 (77.5–98.1) 9.8 89.8 (78.8–95.1) 15.6
25–44 90.8 (82.7–95.1) 12.2 95.5 (81.8–98.9) 13.7 87.7 (60.2–96.2) 10.5
45–64 93.4 (81.6–97.6) 12.2 95.1 (78.8–98.8) 16.3 91.3 (62.8–98.0) 9.5
>65 94.3 (53.2–99.3) 9.8 96.3 (21.1–∞)‡ 11.1 91.8 (27.6–99.1) 9.2
<5 93.9 (87.8–97.0) 12.0 97.3 (87.8–99.4) 25.0 91.7 (82.9–96.0) 11.5
>5 92.5 (88.2–95.2) 13.3 95.4 (88.5–97.5) 13.4 89.8 (82.4–94.1) 13.2
All 92.6 (89.3–94.8) 12.9 95.6 (91.0–97.8) 13.7 90.6 (85.5–93.9) 12.4
Influenza virus types/subtypes§
93.3 (89.5–95.7) 8.6 96.5 (91.4–98.6) 9.4 91.5 (85.7–95.0) 8.3
A(H3N2) 97.3 (93.9–98.8) 6.3 98.6 (93.9–99.7) 7.2 96.7 (91.0–98.8) 6.0
A(H1N1)pdm09 85.4 (73.1–92.0) 2.1 91.0 (64.9–97.7) 1.7 82.9 (65.7–91.5) 2.2
B
92.7 (86.5–96.0)
4.3

94.4 (82.9–98.2)
4.3

91.6 (82.0–96.1)
4.3
Inpatients with severe acute respiratory illness
Age (in years)†
<1 93.5 (72.8–98.5) 4.0 94.3 (11.2–∞)‡ 5.8 93.2 (71.2–98.4) 3.8
1–4 87.9 (73.7–94.5) 7.5 90.2 (61.0–97.6) 10.2 86.5 (66.4–94.6) 6.9
5–24 84.3 (59.5–93.9) 6.6 90.6 (64.6–97.5) 7.2 78.6 (13.6–95.9) 5.9
25–44 83.1 (63.3–92.3) 6.4 90.4 (60.1–97.7) 6.7 75.6 (31.8–91.3) 4.1
45–64 87.3 (63.2–95.6) 6.9 90.9 (54–9-97.7) 8.2 85.2 (29.0–96.9) 5.1
>65 94.5 (57.7–99.3) 8.2 91.5 (18.6–∞)‡ 13.5 91.0 (27.9–98.9) 6.5
<5 89.3 (79.3–94.5) 5.3 91.0 (65.4–97.7) 7.7 89.1 (76.8–94.9) 5.0
>5 86.0 (76.9–91.5) 6.5 91.2 (80.3–96.1) 7.4 79.3 (59.6–89.4) 5.2
All 87.4 (81.3–91.5) 5.9 91.1 (82.2–95.5) 7.4 84.5 (74.7–90.5) 4.9
Influenza virus types/subtypes§
86.7 (78.7–91.7) 3.9 91.3 (79.2–96.3) 4.7 81.9 (68.0–89.8) 3.4
A(H3N2) 93.6 (85.1–97.2) 2.4 94.6 (76.9–98.7) 2.7 92.1 (77.6–97.2) 2.2
A(H1N1)pdm09 80.7 (63.5–89.8) 1.5 88.1 (68.7–97.4) 1.9 71.7 (39.2–86.8) 1.1
B
88.4 (77.6–94.0)
1.9

90.3 (71.5–96.7)
2.7

89.0 (74.2–95.3)
1.4
Inpatients with severe chronic respiratory illness
Age, y†
<1 87.6 (70.7–99.4) 8.0 89. 3(9.3–∞)‡ 8.9 88.1 (72.4–99.8) 7.8
1–4 85.2 (64.8–97.3) 11.1 88.3 (7.4–99.3) 5.6 83.9 (50.9–97.5) 13.3
5–24 81.3 (54.9–92.2) 6.0 85.3 (27.4–95.7) 5.5 78.8 (31.3–93.5) 7.7
25–44 78.7 (43.8–91.9) 3.8 84.6 (35.7–96.3) 4.1 69.5 (32.7–93.0) 3.8
45–64 82.9 (51.1–94.0) 4.6 83.1 (17.6–95.6) 4.2 81.6 (31.5–96.5) 5.5
>65 88.2 (38.4–99.0) 6.4 89.7 (12.0–∞)‡ 6.0 88.0 (11.7–98.7) 6.7
<5 87.1 (73.0–97.4) 9.1 88.6 (52.4–99.0) 7.4 85.1 (71.7–98.1) 9.4
>5 82.7 (70.7–89.8) 4.5 86.9 (64.8–93.2) 4.3 80.2 (60.1–90.2) 5.7
All 86.2 (77.7–91.5) 5.0 87.4 (69.9–93.7) 4.5 82.9 (74.1–92.3) 6.5
Influenza virus types/subtypes§
82.7 (68.6–90.5) 2.9 83.3 (55.8–93.7) 2.7 81.1 (60.5–91.0) 3.5
A(H3N2) 93.1 (81.3–97.4) 2.1 94.8 (64.1–98.6) 1.9 92.7 (75.5–97.8) 2.7
A(H1N1)pdm09 64.5 (32.6–84.6) 0.7 74.2 (17.3–93.8) 0.8 52.8 (9.7–84.5) 0.6
B 91.5 (82.1–95.9) 2.2 92.4 (80.7–97.0) 1.8 88.9 (61.9–96.8) 3.2

*AF, attributable fraction; AF-adjusted prev, prevalence attributable to illness.
†The overall influenza virus AF was obtained from models adjusted for any underlying medical conditions and for other respiratory viruses investigated in this study. Underlying medical conditions were asplenia, including asplenia or sickle cell anemia; chronic illness, including chronic lung, renal, liver, or cardiac disease, diabetes mellitus, and asthma; other immunocompromising conditions (excluding HIV), including organ transplant, primary immunodeficiency, immunotherapy, and malignancy; neurologic disorders; burns; obesity; malnutrition; and prematurity. Comorbidities were considered absent in cases for which the medical records stated that the patient had no underlying medical conditions or when there was no direct reference to that condition. Prematurity and malnutrition were assessed only in analyses for children <1 and <5 years of age, respectively. Age and HIV infection were also included as predictors in nonstratified models.
‡Estimated using exact logistic regression.
‡The influenza virus AF was obtained from models adjusted for age, HIV infection, any underlying medical conditions, and other respiratory viruses investigated in this study, including co-circulating influenza virus types and subtypes.
¶Includes influenza A viruses that were not subtyped.

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Page created: June 19, 2017
Page updated: June 19, 2017
Page reviewed: June 19, 2017
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