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Overview of Influenza

Influenza is a viral illness and is commonly referred to as ‘flu’. It is a contagious illness affecting the respiratory system caused by the influenza viruses. In the USA, on average 5–20% of the population gets the flu every year and about 36,000 people die from flu.1 Influenza typically consists of 4 or 5 days of fever, chills, headache, muscle pain, weakness, and, sometimes, upperrespiratorytract symptoms and cough. Severe complications and deaths can occur, in susceptible populations like infants, elderly and individuals with chronic conditions such as diabetes mellitus and heart disease. Among the most severe complications is pneumonia, which can be associated with secondary bacterial infection.

History: Influenza has caused major pandemics and epidemics worldwide. The first widely studied of influenza pandemic was occurred during 1889—1893.2 There was a ‘Spanish flu’ pandemic during 1918–1919 that is rated among the deadliest publichealth crises in human history, killing an estimated 675,000 people in the USA and an estimated 50–100 million people worldwide.3


Influenza Virus       

Influenza virus can be any of the three types: influenza A, B and C. Influenza A and B viruses cause seasonal viral illnesses in epidemic proportions. Influenza C infections cause a mild respiratory illness in a smaller population.

In the past few years, influenza viruses have managed to grab international headlines due to their epidemic spread. Most often, they are denoted by the name HiNi or H3N2 strain influenza viruses. These are influenza A viruses. The alphabets H and N denote the hemagglutinin and neuraminidase proteins, respectively. These proteins were present on the surface of the virus. There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes. Influenza B viruses are not divided into subtypes. The 1918–1919 influenza pandemic was caused by an influenza A virus of the H1N1 subtype.2

Flu vaccine


Influenza Shot

Influenza shot commonly called as ‘flu-shot’ is the vaccination for influenza. Vaccination remains one of the best options to prevent influenza. The strains of influenza A (H1N1), A (H3N2), and influenza B are included in the influenza vaccine.

Getting a flu shot can protect against influenza A and B viruses. The flu vaccine does not protect against influenza C viruses.

Vaccination provides protection from the disease as well as cost savings for working adults. In a study to assess the cost savings of influenza vaccination, it was found that influenza immunization decreased the frequency of upper respiratory illnesses by 25%, absenteeism from work due to upper respiratory illness by 43%, and physician’s visits for upper respiratory illness by 44%4


Treatment Options

Although vaccination forms the primary fight against influenza, there are some treatment options available after contracting the illness. Influenza treatment comprises of two options. One is the actual treatment of the virus using antiviral medications and the other is focused on alleviation of the symptoms of influenza.

There are two neuraminidase inhibitors that are licensed for their use in USA. These are oseltamivir (Tamiflu®) and zanamivir (Relenza®).

Oseltamivir (Tamiflu®) is approved for the treatment of persons aged above 1 year. It is also licensed for its use as chemoprophylaxis in persons aged 1 year and older.

Zanamivir (Relenza®) is approved for treatment of persons aged above 7 years. It is also licensed for use as chemoprophylaxis in persons aged 5 years and older.

Oseltamivir and zanamivir can reduce the duration of uncomplicated influenza A and B disease by approximately 1 day. Trials suggest that oseltamivir and zanamivir may also prevent serious influenza-related complications (e.g., bacterial or viral pneumonia or exacerbation of chronic diseases) in uncomplicated influenza. The recommended duration of treatment with oseltamivir and zanamivir is 5 days.

Another group of antivirals are the adamantanes—amantadine (Symmetrel®) and rimantadine (Flumadine®). Although these have been effective antivirals against influenza, currently they are not recommended for their use in an outbreak during 2007–2008.5 Surveillance demonstrates that susceptibility to these antiviral medications has been reestablished among circulating influenza A viruses and will be needed before they can be used for the treatment or chemoprophylaxis of influenza A. 

Symptomatic Treatment

These are medications used purely for the symptomatic relief.

Analgesics and antipyretics: Analgesics (pain relieving medications) and antipyretics (fever reducing medications) are used to relieve headaches and body aches. The OTC drugs for these medications that are commonly used are aspirin, acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs).

Decongestants: These are available over-the-counter and can provide much needed symptomatic relief from running nose, stuffy nose etc. Some of the common decongestants are psuedoephedrine and nasal spray decongestants such as phenylephrine or oxymetolazone.


Chemoprophylaxis also plays a very important role in checking the spread of influenza during outbreaks. Both ostelamivir and zanamavir have shown good results for chemoprophylaxis of influenza in studies.

In susceptible populations when there is a spread of influenza, chemoprophylaxis should be initiated whether or not vaccination has been done. It helps in a great way by checking the spread of the illness.


Preventive measures for influenza

In institutions where outbreak or spread can be predicted, stocking up on antiviral medications can be one of the best ways of being prepared for the illness. Getting a physicians recommendation will be helpful for stocking the necessary antivirals..

Written by Healthplus24 Team
Date last updated: April 16, 2012