Influenza - Introduction, Causes, Signs and Symptoms, Prevention, Diagnosis and Treatment

What is Influenza? Causes of influenza, Types of influenza, Mode of transmission, Signs and Symptoms, Diagnosis and Treatment

Introduction

• It is an acute infectious respiratory disease caused by RNA viruses.

• High risk of attack  in all age groups with high mortality rate was observed even in young adults.

• It spread in all countries and effected million of people every year.

• Sunlight, disinfectants, soaps and detergents can inactivate the influenza virus.

•  Frequent washing of hands with soap reduces the risk of infection. 

Causative Agent

• Influenza viruses are RNA viruses which belongs to Orthomyxoviridae family are the main cause of influenza.

•  Many subtypes of viruses are present but influenza A and Influenza B viruses are mainly responsible for influenza.

• Type C influenza virus is mainly associated with sporadic cases and minor localized outbreak.

• Among all virus's influenza A virus is unique among all viruses because it is frequently showing antigenic variations.

Reservoir of Infection

• Major reservoir of influenza virus are birds and animals.

• Many types of influenza viruses have been isolated from animals like cats, dogs, horses etc.

• Animals reservoirs provide new strains of influenza virus by recombination between influenza viruses of man, birds and animals.

Types of Influenza

Influenza has three sub-types:

Influenza A (Potentially serious disease, rapidly changing epidemics and pandemics).

Influenza B (Less serious disease, more uniform epidemics, generally).

Influenza C (Usually mild or asymptomatic, with limited effects on public health).

Incubation period:

Incubation time ranges from one to five days with an average of 2 days.

Mode of Transmission

• Transmission is possible from asymptomatic carriers.

• Influenza virus is mainly transmitted through respiratory droplets of sneezes and coughs from infected person.

• It may transmitted through direct skin to skin contact with infected person or through indirect contact with infected materials, which ultimately leads to the entry of virus through nasopharyngeal route.

Signs and Symptoms

• Cough

• sore throat

• congested conjunctivae

• flushed face

• Vomiting

• Sneezing

• Fever for 2 to 3 days

• Back pain

• weakness and headache

• Pneumonia due to secondary bacterial infection produces more complications.

Diagnosis

1. Diagnosis is based on virus isolation or by serology.
2. Virus is mainly isolated from nasopharyngeal region (throat swabs) or from sputum.
3. Detection of antigen in nasal secretions by immunofluorescence test, antigen capture ELISA, Reverse transcriptase polymerase chain reaction (RT-PCR) are used for diagnosis.

Prevention and Control of Influenza

Following precautions has to be followed to prevent and control influenza:

1. People with symptoms should avoid contact with others. At least 1-meter distance should be maintained with others.

2. While sneezing and coughing, cover the nose and mouth.

3. We should dispose the respiratory secretions using disposable tissues.

4. Tissues after use should be disposed immediately.

5. Good ventilation of the buildings is necessary.

Immunization offers best prospect of controlling influenza. As the antigenic characteristics of the viruses changes from time to time and there is a need for development of new vaccines constantly.

Treatment

a)    Antibiotics like amantadine, rimantadine, oseltamivir are used for bacterial complications of influenza.

b)    Antiviral drugs