According to the Indian Council of Medical Research (ICMR), the unexpected increase in influenza infections in India has been connected to the H3N2 virus, popularly known as "Hong Kong flu." This article explains what exactly the H3N2 influenza virus is along with its symptoms and prevention. 

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In the previous several months, thousands more instances have been reported by hospitals around the nation. H3N2 is a subtype of the influenza A virus. The virus causes respiratory sickness every year. According to a government assessment, there have been few influenza A subtype H3N2-related fatalities in India.

The most common subtype has been H3N2, followed by H1N1. The two strains of influenza A are related to one another. There have also been verified cases of influenza 'B' virus this year (of the Victoria lineage). In contrast to Influenza C and D, these two strains of the flu virus have been linked to actual epidemics in the past.

According to the health ministry's statement, "cases are found to increase during specific months internationally," thus the spike in influenza infections in India isn't unique. The Ministry of Health has said that there are two peak seasons for the virus: January through March and after the monsoons. This year's "seasonal influenza cases are projected to fall from the end of March," it said.

Earlier, the Indian Council of Medical Research (ICMR) said that H3N2 causes more hospitalisations than other influenza subtypes. Six per cent of inpatients had symptoms consistent with pneumonia, and six per cent experienced convulsions. Seven per cent of inpatients had life-threatening illnesses that need intensive care unit treatment, and ten per cent required oxygen therapy.

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Antibiotics prescribtion

1. Antibiotics are not utilised to treat influenza since they are not a part of the treatment procedure for any virus.
2. Doctors will often prescribe antibiotics if a secondary bacterial illness develops.
3. The ICMR has suggested that persons in crowded areas should protect their respiratory systems by using masks.
4. Paracetamol is an over-the-counter medication often used for fever and muscle pains.

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What exactly is the H3N2 influenza virus?

The influenza A, B, C, and D viruses are the four main strains that produce the annual flu season. The H3N2 subtype of influenza A is one of several subtypes that exist. Those born in the late 1960s and 1970s were the first to get the virus as children, and research published in the journal Nature Communications in 2020 discovered that the virus's strains had undergone a remarkable evolution in the preceding five decades.

The H1N1 pandemic was announced by the WHO in June 2009. The swine flu pandemic is another name for this situation. In April 2009, the first instances were recorded in North America. It had already reached 74 nations when the WHO labelled it a pandemic. Being one of the shortest pandemics on record, the swine flu pandemic was declared over in August 2010. Several changes in the new virus have occurred since then, and the swine flu pandemic was declared over in August 2010.

The new A virus, A (H1N1) pdm09, is responsible for the 2009 pandemic. Seasonal influenza vaccinations now contain protection against H1N1 (2009) since it is still circulating as a seasonal virus.

According to the US nodal agency Centers for Disease Control and Prevention, "Influenza A viruses are the only influenza viruses known to produce flu pandemics (i.e. worldwide epidemics of flu sickness). Around a million people died in a global pandemic in 1968 that was also caused by the influenza A H3N2 virus. The Hong Kong flu pandemic of 1968, also known as the Hong Kong flu of 1968, was a global outbreak of influenza that began in China in July 1968 and persisted until 1969-70. After the influenza pandemic of 1957 and the influenza pandemic of 1918–19, this pandemic was the third to occur in the 20th century.

So why is this illness now spreading so rapidly? Experts say the increase in reported instances may be attributed to the fact that "when the virus mutates, the protection that we have against the virus gets a little weaker," making susceptible individuals more vulnerable to infection.

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How does H3N2 manifest its symptoms?

It shares symptoms with other flu strains. Cough, fever, body aches and headaches, sore throat, runny or stuffy nose, excessive exhaustion, and achy joints are some of the symptoms. Several patients have reported stomach issues such as nausea, vomiting, and diarrhoea.

The fever associated with an H3N2 virus often subsides within three days, as reported by the Indian Medical Association (IMA). A persistent cough, however, may last for up to three weeks.

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Which age group is most at risk?

The IMA reports that those under the age of 15 and those over the age of 50 are the most common targets of this virus. High-risk groups include children and those with preexisting diseases including asthma, diabetes, heart disease, compromised immune systems, and neurological or neurodevelopmental disorders.

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How can we stop its spread?

The greatest defence against the transmission of H3N2 is good personal cleanliness. One may lessen their risk of contracting H3N2 by taking preventative measures, such as washing their hands often, using hand sanitizer, and staying away from those who are ill with the virus or the seasonal flu. A healthy diet rich in fruits and vegetables may also play a crucial role in boosting resistance to illness. The expert also recommended eating home-cooked, low-spice, and low-fat cuisine and drinking plenty of water.

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MoHFW guidelines

MoHFW has advised management guidance for seasonal flu. The guiding principles are as follows;

1. Precautions against spreading infections should be put in place as soon as possible during treatment to reduce the likelihood of patients contracting a potentially deadly illness while in a healthcare setting and reduce domestic transmission of illness by regular hand washing, social isolation, etc.
2. Rapid medical intervention to avoid serious sickness and death.
3. Early identification and monitoring of at-risk individuals.

Anti-viral medication: Oseltamivir is the recommended drug for treatment.

Often, empiric antiviral medication is required, and treatment should not be delayed by the findings of confirmatory tests. It is advised to start the therapy as soon as feasible (within 48 hours preferably).

The typical length of treatment is five days. [Clinicians may consider a prolonged course of antiviral medication for patients with a confirmed or suspected immune-compromised state or patients needing hospitalisation for serious diseases of the lower respiratory tract (particularly pneumonia or acute respiratory distress syndrome)]

The recommended dosage for therapy is as follows;

Weight-based age dosage

• <15kg - 1-5 years 30 mg BD for 5 days
• 15-23kg - 5-8 years 45 mg BD for 5 days
• 24-<40kg - 8-12 years 60 mg BD for 5 days
• >40kg - More than 12 years 75 mg BD for 5 days

Supportive treatment for mild flu cases

1. Drink plenty of oral fluids.
2. Intake of paracetamol.
3. Topical decongestants, saline nasal drops, throat lozenges, and steam inhalation may all be helpful for sore throats.
4. Due to the possibility of Reye's syndrome, avoid using salicylate. (in children)
5. Keep a close eye on the underlying, risky condition.

Supportive therapy for patients with high risk

• Antiviral treatment
• IV liquids
• supplementing with O2
• Ensure proper diet, electrolyte balance, and hydration
• Antibiotics for secondary infections
• Ventilatory support
• Vasopressors used to treat shock
• Track your breathing rate, SpO2, and state of consciousness

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Indications of concurrent antibiotics in influenza 

1. The first presentation of patients with severe illness (extensive pneumonia, respiratory failure, hypotension, and fever)
2. Examine and empirically treat bacterial co-infection in individuals who worsen after initial recovery.
3. Patients who do not recover after three to five days of antiviral therapy. ( Antibiotics should be administered in accordance with the recommendations for treating community-acquired pneumonia)

Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Monish Raut is a practising super specialist from New Delhi.