Abstract
This paper describes the epidemiology of hospitalised cases with influenza-like illness (ILI) and laboratory-confirmed influenza A cases in Sicily (Italy) during the 2009 influenza pandemic. The first ILI case diagnosed as infected with pandemic influenza A(H1N1)2009 in Sicily was reported in June 2009 and it rapidly became the dominant circulating strain. In the period from 30 April 2009 through 31 December 2010, a total of 2,636 people in Sicily were hospitalised for ILI and 1,193 were laboratory-confirmed for influenza A. Basic demographic and clinical information for all hospitalised patients was collected and population mortality rates (PMRs) and case fatality ratios (CFRs) were calculated. The median age of hospitalised patients infected with pandemic influenza A(H1N1)2009 was significantly lower than that of hospitalised ILI cases in general (18.0 vs. 32.1 years; p<0.0001). Among adults, women were more susceptible than men. The majority of clinical presentations were mild, but 6.6% of hospitalised patients required admission to an intensive care unit, of whom 26.3% had confirmed influenza A. Twenty-four fatal cases were documented. The age group of 45–54 year-olds showed the highest PMRs once hospitalised, while CFRs were higher in elderly patients of 65 years and older. All fatal cases were confirmed as influenza A(H1N1)2009 and most of them had established risk factors for influenza complications.
Highlights
Before the emergence of the influenza A(H1N1)2009 virus in April 2009 [1], descriptions of clinical illness due to human infection with swine-origin influenza had been limited to sporadic cases and an outbreak on a military base in 1976 [2]
In Sicily, the largest island of Italy with a population of about 5 million inhabitants, the first laboratory-confirmed case of influenza A(H1N1)2009 was detected on 7 June 2009 in a young man returning from the United States, and the first fatal case was reported on 19 September 2009 in a women in her 40s who did not have any underlying diseases or known risk factors
The aim of the present study was to report the influenza surveillance data describing the epidemiological characteristics of patients with influenza-like illness (ILI) symptoms, laboratory-confirmed infections with pandemic influenza A(H1N1)2009, and fatal cases that occurred among hospitalised patients in Sicily from April 2009 through December 2010
Summary
Before the emergence of the influenza A(H1N1)2009 virus in April 2009 [1], descriptions of clinical illness due to human infection with swine-origin influenza had been limited to sporadic cases and an outbreak on a military base in 1976 [2]. In Italy, the virus was first detected on 2 May 2009 in an adult man returning from Mexico [4]. In Sicily, the largest island of Italy with a population of about 5 million inhabitants, the first laboratory-confirmed case of influenza A(H1N1)2009 was detected on 7 June 2009 in a young man returning from the United States, and the first fatal case was reported on 19 September 2009 in a women in her 40s who did not have any underlying diseases or known risk factors. A team of general practitioners and paediatricians (members of the national network INFLUNET) were involved as sentinel practitioners, while several hospital wards throughout Sicily exceptionally participated in the surveillance of hospitalised patients with influenza-like illness (ILI) for severe acute respiratory infection (SARI) potentially related to pandemic influenza A(H1N1)2009
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