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Updated: Aug 9, 2026

Rapid Molecular Detection and Differentiation of Influenza Viruses A and B
Published on: January 30, 2017
[Clinical characteristics of children hospitalized for influenza virus infection]
N Arostegi Kareaga1, M Montes, E G Pérez-Yarza
1Servicio de Pediatría, Hospital Donostia, San Sebastián, Spain. arostegi@chdo.osakidetza.net
Insights
Influenza virus infection in hospitalized children often presents with nonspecific symptoms, particularly in infants under six months. Early diagnosis requires specific testing, as healthy infants under 24 months are most vulnerable.
Area of Science:
- Pediatric Infectious Diseases
- Virology
- Epidemiology
Context:
- Influenza virus infections present with nonspecific symptoms, mimicking other serious conditions in neonates.
- Limited research exists on the clinical characteristics of influenza in hospitalized children.
Purpose:
- To evaluate the clinical characteristics of children hospitalized with influenza virus infection.
- To analyze data from four consecutive influenza epidemic waves (2000-2004).
Summary:
- Eighty-four children were hospitalized, predominantly with influenza A (H3N2).
- Common symptoms included fever, cough, and ENT involvement, with febrile syndrome being the most frequent admission reason.
- Infants under six months represented 42.8% of cases; pneumonia and prolonged fever were more common in older children.
Impact:
- Identifies previously healthy neonates with nonspecific symptoms as the most affected group.
- Highlights the need for specific microbiological diagnostic techniques for early influenza diagnosis in children.
- Determines that healthy infants under 24 months are at the highest risk for influenza-related hospitalization.
Background:
The clinical manifestations of influenza virus are fairly nonspecific and are similar to those of other viral infections, respiratory processes due to other causes and even septic disease in neonates. Few studies have been performed of the clinical characteristics of influenza virus infection in hospitalized children.
Objective:
To evaluate the clinical characteristics of children hospitalized for influenza virus infection in four consecutive epidemic waves (2000-2004).
Material And Methods:
We retrospectively reviewed the medical records of children hospitalized for influenza A and B virus infection confirmed by cell culture and polymerase chain reaction. Age, sex, symptoms on admission, complementary investigations, diagnosis and outcome were evaluated.
Results:
Eighty-four children were hospitalized, of which 74 had influenza virus type AH3, five had influenza virus type AH1 and five had influenza B virus. A total of 42.8 % were aged less than 6 months. The main symptoms were fever (75 patients), cough (56 patients) and ENT involvement (53 patients). The most frequent causes of admission were febrile syndrome (75 patients), bronchiolitis (19 patients), pneumonia (13 patients) and bronchitis (8 patients). In 21 patients viral or bacterial coinfection was found, the most frequent of which was respiratory syncytial virus (10 patients). Few differences were found among age groups except for pneumonia and prolonged fever (more frequent in children older than 6 months) and lymphocytosis (in children younger than 6 months). The greatest number of complementary investigations in younger children was performed for acute febrile syndrome in neonates aged less than 6 months. Risk factors for hospitalization were found in only three children, all of whom were older than 6 months. Outcome was favorable in all children.
Conclusions:
Influenza virus infection in hospitalized children is most frequent in previously healthy neonates with fever and nonspecific signs and symptoms that are similar to those of other infectious processes. Specific microbiological diagnostic techniques are required for an early diagnosis. Healthy infants aged less than 24 months are most at risk for hospitalization for influenza virus infection.
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Stages of Infection
Acute Pharyngitis
Acute pharyngitis is the inflammation of the back of the throat (pharynx), commonly resulting in a sore throat. It is a frequently encountered condition that prompts individuals to seek medical advice.
Classification
Acute pharyngitis can be categorized based on its underlying cause:
Atypical Pneumonia
Viral Meningitis
Influenza
Respiratory Syncytial Virus Disease

