Introduction

Influenza is a highly infectious viral illness caused by influenza virus. It is a single stranded, helically shaped, RNA virus of the orthomyxovirus family. Basic antigen types A, B, and C are determined by the nuclear material. Type A influenza has subtypes that are determined by the surface antigens hemagglutinin (H) and neuraminidase (N). Three types of hemagglutinin in humans (H1, H2, and H3) have a role in virus attachment to cells. Two types of neuraminidase (N1 and N2) have a role in virus penetration into the cells.

Signs and Symptoms

Fever or feeling feverish/chills
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue

Transmission

It is believed that flu viruses spread mainly by droplet made when people with flu cough, sneeze or talk.
These droplets can land in the mouths or noses of people who are nearby.
Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes or possibly their nose.

Pathogenesis

Respiratory transmission of virus.
Replication in respiratory epithelium with subsequent destruction of cells.
Viremia rarely documented.
Virus shed in respiratory secretions for 5-10 days.

Diagnosis

It is very difficult to distinguish the flu from other viral or bacterial causes of respiratory illnesses on the basis of symptoms alone.
A number of flu tests are available to detect influenza viruses. The most common are called “rapid influenza diagnostic tests.”

Prevention and Treatment

The first and most important step in preventing flu is to get a flu vaccination each year.
Antiviral drugs are prescription medicines that fight the flu in the body.
The FDA-approved influenza antiviral drugs are: Oseltamivir, Zanamivir, and Peramivir.