After the Covid pandemic, another virus is on the verge of an outbreak. However, it is rather an expected outbreak due to its characteristic of reassortment – H3N2 flu.
The H3N2 flu is a type of influenza A virus first introduced in 1968 that lead to a major pandemic. Thereafter, H3N2 flu led to 4-5 major outbreaks around the world. H3N2 strain most likely originated from reassortment that occurred between human H2N2 flu and avian H3N2 flu which resulted in the development of novel human H3N2 strains. Reassortment means the exchange of genetic materials between 2 viruses that lead to a new hybrid virus. It is particularly present in Influenza viruses as they are segmented viruses containing 8 separate RNA segments.
Classification of H3N2 flu
Influenza A virus has 2 types of surface glycoproteins:
- Hemagglutinin (HA)
- Neuraminidase (NA)
Hemagglutinin is responsible for binding the virus to the host cell which helps in its entry into the cell. While Neuraminidase is responsible for the release of newly formed virions of influenza from infected cells and spread through other healthy cells. There are 18 subtypes of Hemagglutinin numbered H1-H18 and 11 subtypes of Neuraminidase numbered N1-N11. The influenza A viruses are classified based on the presence of these subtypes of surface glycoproteins, e.g. H3N2, H1N1, H2N2, etc.
The H3N2 flu is known for its ability to mutate easily. This mutation occurs mostly in the surface glycoproteins due to which, the antibodies have a hard time trying to identify viral proteins and kill them. As a result, the virus evades the immune system of the host easily and creates major outbreaks periodically. Hence, special guidelines have been created to update the vaccination against the H3N2 strain every year to combat such a highly mutative virus.
How does the H3N2 flu spread?
The H3N2 flu primarily spreads through respiratory droplets via coughing, sneezing, talking, etc. of an infected person. A healthy person could inhale such respiratory droplets when staying in proximity to an infected individual.
It can also spread while touching any objects such as utensils, stationery items, etc. that are contaminated with infected respiratory droplets and then touching your mouth or nose with the same hand. Such objects are called fomites.
Once you are infected, these viruses travel through your respiratory tract and begin to replicate. The virus triggers an immune response, which can cause inflammation and damage to the respiratory tract. However, the severity of the infection can vary widely, depending on factors such as the age and overall health of the person infected.
Symptoms of H3N2 flu
The symptoms of H3N2 flu appear 1-4 days after the person is affected. However, symptoms vary according to the individual. Common symptoms are:
- Fever
- Cough
- Runny nose
- Headache
- Sore throat
- Fatigue
Some additional symptoms include:
- Bodyache
- Nausea
- Vomiting
- Diarrhea
Some cases can become severe which can lead to complications leading to hospitalizations. Such complications are more common in elderly and immunocompromised people. Some complications are:
- Pneumonia
- Bronchitis
- Worsening of an underlying medical condition such as asthma, diabetes, or heart disease.
How to prevent H3N2 flu
The best way to avoid the spread of H3N2 flu is by curbing the transmission through respiratory droplets.
- Maintain proper hygiene and sanitation
- Frequent Hand washing
- Avoiding close contact with infected persons
- Cover the mouth and nose with a handkerchief while talking, sneezing, or coughing
- Drinking plenty of fluids and proper rest
Vaccination is another strategy to combat H3N2 flu. Seasonal influenza vaccines are developed every year to fight against recommended strains of influenza that are more likely to cause infection. According to the Centers for Disease Control and Prevention (CDC), seasonal influenza vaccines are quadrivalent vaccines i.e. they contain four different influenza strains. Two strains of Influenza A: H1N1 and H2N3 and two strains of Influenza B: Yamagata and Victoria lineages. WHO recommends updating the strains of influenza annually in seasonal influenza vaccines as influenza viruses have a higher tendency to mutate.
Since the virus mutates every year, the efficacy of the H3N2 strain of the vaccine varies every year. One of the major reasons for outbreaks of influenza virus is the reduced efficacy of the respective strain of influenza to stimulate the immune system of the host body. This happens due to the mutation of the influenza virus that alters its glycoproteins structure and function. The H3N2 strain is an inactivated or killed component of the vaccine that stimulates the immune system once it is inoculated in the body.
Treatment
The most common medications against H3N2 flu are Oseltamivir (Tamiflu) and Zanamivir (Relenza). These antiviral medications act on surface glycoproteins: Hemagglutinin and Neuraminidase and block their activity which prevents the spread of the virus inside the body.
Other treatments include drugs to alleviate the symptoms of H3N2 flu. These medications include:
- Antihistamines to alleviate runny nose, and itchy or watery eyes
- Pain medications such as paracetamol or ibuprofen for body aches and headaches.
If the condition becomes severe, hospitalization may be required where mechanical ventilation and supplemental O2 therapy can be provided. It is necessary to visit a nearby hospital if you belong to:
- Children 5 years or younger
- People 65 years or older
- Pregnant people
- Immunocompromised people
- People with long-term complications such as heart disease, asthma, diabetes, etc.
Conclusion
H3N2 virus is a notorious and highly mutative virus. Because of its tendency to easily mutate, it is pretty hard to create a vaccine that can combat such a virus. Hence, scientists have recommended taking the new flu shots periodically. A flu shot has an effective period of about 3-6 months. Every 6 months, a newly developed flu shot is distributed around the world. It is necessary to take those flu shots at least annually and especially during times of outbreak, to prevent any infection.
Moreover, people who are immunocompromised or at the extremes of their age should take necessary precautions to avoid any infection. H3N2 infection can become severe in these groups. It is to be noted not to take any self-prescribed over-the-counter medications to alleviate the symptoms. Kindly visit your nearby doctor for the correct diagnosis and prescription. Taking the prescribed antiviral drugs within 48 hours of the onset of symptoms has a much better prognosis. These will help you protect yourself and your loved ones.
