Influenza A is responsible for flu pandemics owing to the presence of 2 surface proteins on the virus- haemagglutinin (H) and neuraminidase (N). The subtypes of the influenza A virus, H1N1 and H3N2, have been found to cause flu pandemics. Both these subtypes change genetically as well as antigenically to produce variants. H3N2 tends to change more rapidly, both genetically and antigenically, compared to H1N1. As per the World Health Organisation (WHO) report, H3N2 viruses have been responsible for considerable mortality.

Symptoms:

The symptoms associated with the H3N2 virus resemble other respiratory viruses, including fever, sore throat, nasal discharge, headache, coughing, myalgia, and nasal discharge. In severe cases, pneumonia and bronchitis could happen, thereby leading to death. 

Diagnostic evaluation:

H3N2 influenza virus detection techniques have been classified into four categories:

• Traditional methods: Virus culture comes under the class of traditional methods.
• Serological methods: These include:

1. Immunofluorescence assays
2. Complement fixation
3. Immunodiffusion test
4. Virus neutralisation method
5. Haemagglutination method
6. Rapid antigen testing.

• Advanced quick methods: These methods are based on the molecular biology of elements. It includes:

1. Rapid influenza technique
2. Real-Time polymerase chain reaction (PCR)
3.  Multiplex PCR
4. Non-PCR-based RNA-specific detection methods, such as nucleic acid sequence-based amplification (NASBA)
5. Conventional PCR.

It has been found that nasopharyngeal swabs yield higher rapid detection of influenza instead of nasal and throat swabs.

• Bio-sensing methods: These methods include:

1. Optical biosensors
2. Giant magneto-resistance biosensors
3. Aptamer-based biosensors
4. Electrochemical biosensors.^[1]

Comparative analysis of the detection techniques:

Treatment:

Symptomatic therapy is advised for patients that are not from a high-risk group. They are also recommended to stay home to minimise the risk of disease transmission to other members of the community.

Preventive measures:

Influenza vaccines, though, generally have variable and only moderate efficacy; they remain a critical preventive strategy for controlling the disease and its consequences.

The egg-based quadrivalent vaccines have been recommended by the Indian Council of Medical Research (ICMR) for administration in the 2020-2021 northern hemisphere influenza season containing the following composition:

• An A/Guangdong-Maonan/SWL1536/2019 (H1N1) pdm09-like virus;
• An A/Hong Kong/2671/2019 (H3N2)-like virus;
• A B/Phuket/3073/2013 (B/Yamagata lineage)-like virus; and
• A B/Washington/02/2019 (B/Victoria lineage)-like virus.^[2]

The Centers for Disease Control and Prevention (CDC) recommendations for patients at high risk:

The people who are at high risk of serious flu complications, including individuals 65 years and older, children younger than 5 years,  pregnant women, and individuals with certain chronic medical conditions (like diabetes, asthma, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions), are advised not to go to areas where pigs are present.