What You Should Know About H3N2 Flu

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Close up of flu virus. Ian Cumin/Ikon Images/Getty Images

H3N2 Flu is a subtype of influenza A. Although they are multiple types of influenza, only influenza A is further broken down into subtypes. These subtypes are actually broken down even further as they are identified by the World Health Organization (WHO) based on:

  • Host of origin (type of animal in which virus was first identified - swine, bird, etc.; for human origin, no host is listed)
  • Geographical origin (location/city in which virus was first isolated)
  • Strain number
  • Year of isolation

Each year there are variants of influenza that cause illness during flu season. The virus mutates, making it difficult to predict which one will make people sick each year or even how severe the season will be.

When WHO officials choose the strains of influenza to include in the yearly flu vaccine, they choose two strains of influenza A (one variant of H1N1 and one variant of H3N2) and one or two strains of influenza B. Most flu vaccines contain three strains of influenza but the quadrivalent vaccine and the nasal spray vaccine, Flu Mist, contain four (two strains of influenza B instead of one). These strains are chosen over 6 months before flu season starts because it takes that long to manufacture and prepare those vaccines for distribution.

What To Expect From H3N2

Although flu symptoms are typically similar no matter the strain of influenza, history has shown that seasons in which H3N2 influenza A is the dominant strain have been more severe.

From 2003 to 2013, the three flu seasons that were dominated by H3N2 strains of the flu had the highest mortality rates - causing more deaths on average than other years (excluding the 2009 H1N1 pandemic flu).

At the beginning of the 2014-2015 flu season, a mutated version of H3N2 has caused a majority of the flu in the United States.

The mutated virus is different from the strain of H3N2 influenza A that is included in the season's vaccine. Unfortunately that means the vaccine may not provide as much protection against the flu as it would otherwise. However, that doesn't mean it doesn't work at all.

No matter what, you need to know what to expect from the flu. Whether it is caused by H3N2 influenza A or another strain, typical flu symptoms include:

  • Body Aches
  • Fever
  • Headache
  • Sore Throat
  • Cough
  • Exhaustion
  • Minor Congestion
  • Vomiting and Diarrhea - uncommon, occurs more frequently in children

Diagnosis and Treatment

Only your health care provider can diagnose you with the flu. A diagnosis is made based on symptoms you are experiencing, a physical exam and sometimes a rapid flu test that is performed using a nasal or throat swab.

If your health care provider determines that you have the flu, treatment can vary depending on your age, overall health and length of time that you have been sick.

You may be prescribed an antiviral medication (such as Tamiflu or Relenza) that can help shorten the severity of your symptoms or the duration of your illness.

However, these medications are most effective if taken within the first 48 hours of the onset of symptoms, so if you have been sick longer than that, your provider may decide that taking them won't really benefit you. You may also be told that you don't need an antiviral medication if you are not at high risk for flu complications.

Even without antiviral medications, there are things you can do to help yourself feel better. Taking over the counter medications to alleviate your symptoms, getting plenty of rest and drinking lots of fluids are important things you can do to give your body a chance to recover. Taking antibiotics won't help unless you have a secondary bacterial infection because antibiotics don't kill viruses.

Sources:

"Early Data Suggests Potentially Severe Flu Season". CDC Newsroom Releases 4 Dec 14. US Centers for Disease Control and Prevention. Department of Health and Human Services. 

"Flu Symptoms & Severity". Seasonal Influenza (Flu) 15 Aug 14. US Centers for Disease Control and Prevention. Department of Health and Human Services. 

"How the Flu Virus Can Change: 'Drift' and 'Shift'". Seasonal Influenza (Flu) 19 Aug 14. US Centers for Disease Control and Prevention. Department of Health and Human Services. 

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