Surveillance Of Acute Respiratory Infections Research Articles

A study of excess mortality during influenza epidemics in the Czech Republic, 1982–2000

Influenza related mortality rates have been established in many countries; nevertheless, studies focusing on the Central European population have been rare to date. We assess mortality attributable to influenza by comparing all cause mortality and mortality due to diseases of the circulatory system during influenza epidemic and non-epidemic periods, as defined by acute respiratory infection surveillance data. Data on total mortality, mortality due to diseases of the circulatory system and surveillance data for influenza and other respiratory infections were used in a general linear model with a logarithmic link for dependence of left censored mortality data over time, and week as a categorical factor. Results of the analysis show statistically significant (p <0.001) differences in excess mortality rates between influenza epidemic and non-epidemic periods in the Czech Republic between 1982 and 2000. We estimate that 2.17% of all cause mortality, and 2.57% of mortality due to diseases of the circulatory system throughout the study period was attributable to influenza, with an estimated annual average of 2661 and 1752 deaths respectively. The highest numbers of deaths were reported during seasons when influenza A/H3N2 was the predominant circulating strain. Improving vaccination coverage against influenza is considered to be the primary strategy for prevention of influenza associated mortality.

Respiratory syncytial virus infection: denominator-based studies in Indonesia, Mozambique, Nigeria and South Africa.

To assess the burden of respiratory syncytial virus (RSV)-associated lower respiratory infections (LRI) in children in four developing countries. A WHO protocol for prospective population-based surveillance of acute respiratory infections in children aged less than 5 years was used at sites in Indonesia, Mozambique, Nigeria and South Africa. RSV antigen was identified by enzyme-linked immunosorbent assay performed on nasopharyngeal specimens from children meeting clinical case definitions. Among children aged < 5 years, the incidence of RSV-associated LRI per 1000 child-years was 34 in Indonesia and 94 in Nigeria. The incidence of RSV-associated severe LRI per 1000 child-years was 5 in Mozambique, 10 in Indonesia, and 9 in South Africa. At all study sites, the majority of RSV cases occurred in infants. These studies demonstrate that RSV contributes to a substantial but quite variable burden of LRI in children aged < 5 years in four developing countries. The possible explanations for this variation include social factors, such as family size and patterns of seeking health care; the proportion of children infected by human immunodeficiency syndrome (HIV); and differences in clinical definitions used for obtaining samples. The age distribution of cases indicates the need for an RSV vaccine that can protect children early in life.

Surveillance of influenza and other acute respiratory infections: weekly monitoring and impact on paediatric population during 2000–2001 and 2001–2002 seasons in 10 Italian regions

The total burden of acute respiratory diseases in children is still not completely understood. Clinical and epidemiological surveillance of influenza (FLU) and other Acute Respiratory Infections (ARI) are currently a major objective of Public Health in order to approach “ad hoc” prevention strategies in pediatric population. The principal aim of our study was to describe the epidemiology of these diseases using an appropriate surveillance system. During 2000–2001 and 2001–2002 seasons, respectively 49 and 55 sentinel paediatricians monitored 10 Italian Regions (Liguria, Lombardy, Friuli Venezia Giulia, Tuscany, Umbria, Marche, Abbruzzo, Puglia, Calabria and Sicily) weekly notifying FLU, monitored as Influenza Like Illness (ILI), and ARI clinical cases. We calculated cumulative weekly morbidity rate×1000 subjects between 0 and 14 years during winter season (44th to 17th week). The FLU vaccinal status and the number of hospitalisations were also looked into.

Italian influenza surveillance network: results of the first year of activity. The Collaborative Group for influenza surveillance.

The spread of influenza is of major public health concern. Community based clinical morbidity data constitute an excellent predictor of when the peak of influenza virus activity will be reached. Surveillance programmes exist in many countries [1, 2]. A voluntary system for the surveillance of acute respiratory infection (ARI) and influenza was established in Italy in 1996. The surveillance is based on a sentinel network of general practitioners (GPs) and pediatricians (Ps) for the collection of clinical data and a network of virological laboratories. The physicians report to the Istituto di Virologia on a weekly basis.

Epidemiology of acute respiratory infections

Nearly 25% of all deaths among children less than 5 years of age in developing countries are caused by acute respiratory infections (ARI). Estimates of annual mortality rates for ARI in infants range from 1.5 per 1,000 in North America to from 11 to 15 in 1,000 per Central and South America and Africa. Annual mortality rates for ARI for children 1 to 4 years of age ranged from 0.08 per 1,000 in North America to 1 to 1.5 per 1,000 in Central and South America and in Asia to nearly 5 per 1,000 in Africa. The economic consequences of even relatively benign ARI are substantial. In the United States, consumers spend about $2 billion per year for over-the-counter medications for ARI, and the total annual cost of ARI managed in outpatient settings is estimated to be more than $10 billion. There has been substantial variation both in the definitions of ARI and in methods of surveillance for ARI in various studies. Despite this, in most studies, infants and young children had 6 to 8 episodes per year of ARI. Although the frequency of ARI was similar in both developed and developing countries, the case-fatality rate is much higher in developing countries. It may be possible to prevent some of these serious infections with new vaccines against important causes of ARI in children (or with better distribution of currently available vaccines).

Respiratory syncytial virus or influenza?

We compared data from clinical surveillance of acute respiratory infections in elderly people reported by a network of sentinel general practitioners, virus isolate data for respiratory syncytial virus (RSV) and influenza A and B viruses, and registered deaths, during the past four winters. Cases of acute respiratory disease (ARD) and deaths (3-week moving averages) showed strong similarity in timing. Periods of high incidence of ARD and numbers of deaths were followed within 2-3 weeks by reports of high numbers of RSV or influenza virus isolates. The epidemic period in December, 1989, was followed by high numbers of both virus isolates, but in all other epidemic periods one virus predominated. The lethality of epidemics due to RSV or influenza A or B varied both within and between years. These analyses suggest that RSV is as important as influenza viruses in causing morbidity and excess deaths among elderly people. RSV was prevalent at the end of each of the past four years in the UK; its importance as a cause of excess deaths would therefore be concealed in any analysis based on several years' experience. By contrast, the inconsistency of epidemics due to influenza viruses makes excess deaths due to these viruses easily recognisable. Integrated clinical and viriological surveillance is essential if epidemics due to RSV, influenza virus, or any other virus are to be correctly interpreted.

Five years of sentinel surveillance of acute respiratory infections (1985–1990): The benefits of an influenza early warning system

For the last five years, the Brussels Institute of Hygiene and Epidemiology has been involved in the surveillance of acute respiratory infections (ARI). The four indicators used (number of encounters of ARI by GP's/100 encounters, virus isolations, absenteeism and mortality) are discussed. A regression procedure is applied to the data collected by a sentinel network of general practitioners (GP's). This procedure permits the baseline to be visualized and an epidemic threshold to be determined in order to recognize early an influenza outbreak. The traditional use of flu-like illnesses as an indicator might be improved by the addition of non-specific ARI which are more precocious, especially in children. The criteria for an accurate definition of an influenza epidemic are discussed. The same mathematical model can be used for the analysis of mortality linked with an outbreak. It shows that the last epidemic in the winter 1989-1990 was responsible for about 4900 deaths directly or indirectly related to influenza.

Postal surveillance of acute respiratory virus infections in general practice

Two years' surveillance of acute respiratory virus infections in general practice populations is reported. The normal postal service was used for transportation of specimens for virus isolation from patient to laboratory. Most common respiratory viruses were isolated with discrete outbreaks of influenza virus types A and B, respiratory syncytial virus and paramfluenza virus types 1 and 3. The rate of virus isolation from general practice survey specimens was found to be remarkably similar to that from specimens freshly collected from hospital patients during the same 2 years. For surveillance of respiratory viruses in a community the method provided an alternative to studies of hospital patients.

Surveillance of acute respiratory virus infections in general practice.

The ordinary postal system provides a simple method for the transportation of specimens for virus isolation to the laboratory. This was used to carry out an epidemiological survey, in general practice, of respiratory viruses in patients with acute respiratory disease. Three distinct outbreaks of myxovirus infections were recognized and most other types of respiratory viruses were isolated sporadically. After the initial "pilot" phase of the study an isolation rate of 24% was obtained over the months from October 1968 to June 1969 (20% isolations from adults' specimens and 29% from those of children).