Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. It spreads easily, with rapid transmission in crowded areas including schools.

SYMPTOMS

Seasonal influenza is characterized by a sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a runny nose. The cough can be severe and can last 2 or more weeks.

Most people recover from fever and other symptoms within a week without requiring medical attention. But influenza can cause severe illness or death especially in people at high risk.

DIAGNOSTIC

The majority of cases of human influenza are clinically diagnosed.

Collection of appropriate respiratory samples and the application of a laboratory diagnostic test is required to establish a definitive diagnosis. Proper collection, storage and transport of respiratory specimens is the essential first step for laboratory detection of influenza virus infections.

Laboratory confirmation of influenza virus from throat, nasal and nasopharyngeal secretions or tracheal aspirate or washings is commonly performed using direct antigen detection, virus isolation, or detection of influenza-specific RNA by reverse transcriptase-polymerase chain reaction (RT-PCR).

PREVENTION

The most effective way to prevent the disease is vaccination.

EPIDEMIOLOGY

Seasonal influenza represents a year-round disease burden. It causes illnesses that range in severity and sometimes lead to hospitalization and death.

Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness, and about 290,000 to 650,000 respiratory deaths.

REFERENCES
 

1. Warren-Gash C, et al. (2018) Laboratory-confirmed respiratory infections as triggers for acute myocardial infarction and stroke: a self-controlled case series analysis of national linked datasets from Scotland. Eur Resp J 51:1701794; DOI: 10.1183/13993003.01794-2017 
   Date Accessed: June 30, 2023

2. Kubale J, et al. (2021) Individual-level association of influenza infection with subsequent pneumonia: a case-control and prospective cohort study. Clin Infect Dis 73:e4288-e4295; DOI: 10.1093/cid/ciaa1053
   Date Accessed: June 30, 2023

3. WHO Influenza Fact Sheet. https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)
   Date Accessed: June 30, 2023

Frequently Asked Questions

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