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Clin Infect Dis. 2019 Aug 30;69(6):1036-1048. doi: 10.1093/cid/ciy1017.

Quantifying How Different Clinical Presentations, Levels of Severity, and Healthcare Attendance Shape the Burden of Influenza-associated Illness: A Modeling Study From South Africa.

Author information

1
Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
2
Influenza Program, Centers for Disease Control and Prevention, Pretoria.
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
School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
7
Department of Medicine, Pietermaritzburg Metropolitan Hospital, South Africa.
8
Caprisa, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
9
Department of Medicine, Klerksdorp-Tshepong Hospital Complex, South Africa.
10
Department of Medicine, Faculty of Health Sciences, South Africa.
11
Perinatal Human Immunodeficiency Virus Research Unit, South Africa.
12
Medical Research Council, Respiratory and Meningeal Pathogens Research Unit, South Africa.
13
Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa.

Abstract

BACKGROUND:

Burden estimates of medically and nonmedically attended influenza-associated illness across syndromes and levels of severity are lacking.

METHODS:

We estimated the national burden of medically and nonmedically attended influenza-associated illness among individuals with different clinical presentations (all-respiratory, all-circulatory, and nonrespiratory/noncirculatory) and levels of severity (mild, fatal, and severe, nonfatal) using a combination of case-based (from laboratory-confirmed influenza surveillance) and ecological studies, as well as data from healthcare utilization surveys in South Africa during 2013-2015. In addition, we compared estimates of medically attended influenza-associated respiratory illness, obtained from case-based and ecological studies. Rates were reported per 100 000 individuals in the population.

RESULTS:

The estimated mean annual number of influenza-associated illness episodes was 10 737 847 (19.8% of 54 096 705 inhabitants). Of these episodes, 10 598 138 (98.7%) were mild, 128 173 (1.2%) were severe, nonfatal, and 11 536 (0.1%) were fatal. There were 2 718 140 (25.6%) mild, 56 226 (43.9%) severe, nonfatal, and 4945 (42.8%) medically attended should be after fatal episodes. Influenza-associated respiratory illness accounted for 99.2% (10 576 146) of any mild, 65.5% (83 941) of any severe, nonfatal, and 33.7% (3893) of any fatal illnesses. Ecological and case-based estimates of medically attended, influenza-associated, respiratory mild (rates: ecological, 1778.8, vs case-based, 1703.3; difference, 4.4%), severe, nonfatal (rates: ecological, 88.6, vs case-based, 75.3; difference, 15.0%), and fatal (rates: ecological, 3.8, vs case-based, 3.5; difference, 8.4%) illnesses were similar.

CONCLUSIONS:

There was a substantial burden of influenza-associated symptomatic illness, including severe, nonfatal and fatal illnesses, and a large proportion was nonmedically attended. Estimates, including only influenza-associated respiratory illness, substantially underestimated influenza-associated, severe, nonfatal and fatal illnesses. Ecological and case-based estimates were found to be similar for the compared categories.

KEYWORDS:

South Africa; burden; influenza; rates

PMID:
30508065
DOI:
10.1093/cid/ciy1017

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