Delhi Battles H3N2 Surge: Top 7 Reasons Behind the Flu Outbreak Explained

As monsoon rains taper off, Delhi and the surrounding NCR region are facing a rising wave of viral illness. Nearly 69% of households in Delhi-NCR report that one or more family members are down with symptoms like fever, cough, sore throat and respiratory distress. The dominant culprit is known to be the H3N2 influenza A virus.

According to the reports, this outbreak is more severe than typical seasonal flu, has longer fevers, harder-to-treat symptoms, and more hospitalisations, especially among children, older adults, and those with pre-existing health conditions. In an exclusive interaction with the editorial team of Onlymyhealth, our expert, Dr Bhumesh Tygai, Senior Consultant and General Physician, Sharda Hospital - Noida, explained to us the main causes of H3N2 and its prevention tips. Read ahead to find out.

Causes Of the H3N2 Virus

Here are seven main causes contributing to this surge, according to Dr Tyagi: 

1. Post-monsoon Weather Changes and Humidity Fluctuations

After heavy monsoon rains, humidity and temperature fluctuations favour viral survival and transmission. Cool nights and warm days can stress the immune system, and damp conditions allow respiratory viruses to linger in the air and on surfaces longer.

2. Increased Crowding and Indoor Congregation

As people avoid rainy, damp outdoors, more time is spent indoors, such as in homes, public transport, schools, and offices, often with poor ventilation. This aids in the droplet transmission of flu viruses, such as H3N2.

Also Read: Symptoms And Treatment Of H3N2 Virus That You Must Know

3. Pollution and Compromised Air Quality

Delhi regularly experiences poor air quality, which irritates the respiratory tract, weakens lung defences, and makes it easier for viral infections to take hold. Individuals with respiratory conditions are affected more severely.

4. Virus Mutation and Viral Virulence

Influenza viruses mutate regularly. H3N2 is known to shift, which may make existing immunity less effective, and can lead to worse symptoms. The season’s dominant strain seems more aggressive in some cases.

5. Lower Immunity Due to Previous Low Exposure / Behavioural Fatigue

During COVID-19, mask use, distancing, and other precautions reduced the spread of many respiratory viruses. Following the relaxation of these measures, regular exposure (which helps build immunity) has been low. Also, as people resume normal social interaction, the virus finds more susceptible hosts.

5. Delay in Seeking Medical Attention & Self-Medication

Many people attempt over-the-counter remedies first. Delays in getting proper treatment can worsen illness or allow complications. The longer duration of fever, cough, and symptoms even after initial treatments is being reported.

7. Vulnerable Population and Comorbidities

Elderly people, young children, pregnant women, and those with chronic health problems like asthma, diabetes, and heart disease are more likely to have severe illness. In a large outbreak, such groups push up hospitalisations. Under-nutrition, lack of rest, and weakened immunity also amplify risks.

Preventive Steps for H3N2 Virus

Here are a few preventive measures you can take to safeguard yourself and your loved ones:

• Get the annual flu vaccine, especially people in high-risk groups.
• Practice good respiratory hygiene: frequent hand-washing, masks in crowded or enclosed spaces, covering coughs/sneezes.
• Ensure good ventilation in homes, workplaces, and schools.
• Rest, hydration, and proper nutrition to support immunity.
• Be alert: if fever persists beyond a few days, or symptoms worsen (breathlessness, chest pain), seek medical attention.
• Avoid self-medicating unnecessarily, especially with antibiotics (which do not work against viruses).

Bottomline

The rise of H3N2 in Delhi-NCR is a reminder that even familiar viruses can become serious threats under the right conditions. Understanding what is driving the current surge helps individuals and public health authorities target prevention and response more effectively. With vigilance, vaccination, and responsible behaviour, the impact can be mitigated.

FAQs on H3N2 in Delhi

1. What is H3N2, and how is it different from the common flu?

H3N2 is a subtype of Influenza A that causes more severe symptoms, longer fever, and higher chances of complications compared to seasonal flu.

2. Who is at the highest risk of severe illness from H3N2?

Children, elderly people, pregnant women, and those with chronic health conditions like asthma, diabetes, or heart disease are most vulnerable.

3. Can vaccination help prevent H3N2 flu?

Yes, the annual flu vaccine provides protection and reduces the risk of severe illness, especially for high-risk groups.