Over the past few weeks, Delhi-NCR has seen a sharp increase in viral illnesses. According to a LocalCircles survey of over 11,000 households, 69% reported at least one member displaying symptoms such as fever, cough, sore throat and respiratory distress. Compared to earlier in the year (e.g. March 2025, when around 54% of households reported similar symptoms), the current outbreak represents a significant escalation. Doctors and virologists point to influenza A's H3N2 subtype as the leading driver of this surge. What's unusual this season, however, is how many cases are more severe than typical seasonal flu, i.e. fevers lasting longer, over-the-counter drugs being less effective, and more hospitalisations, especially among vulnerable groups.
Given Delhi's dense population, high co-morbid disease burden (diabetes, respiratory illness, cardiac conditions), and extended monsoon conditions aiding viral spread, the situation is a public health concern. Prompt awareness, correct diagnosis, prevention and care can make a big difference before it worsens. So, here's everything you need to know
What Is H3N2 Virus?
H3N2 is a subtype of Influenza A virus. Influenza viruses are categorised by surface proteins (haemagglutinin "H" and neuraminidase "N"). So, H3N2 refers to the type-3 H and type-2 N. It is one of the strains that causes seasonal flu, meaning it circulates in humans, mutates over time, and each season may have differing severity. It tends to cause more severe symptoms in high-risk populations:
- Children,
- Older adults,
- Pregnant women,
- People with weakened immune systems, and
- Those with underlying conditions such as asthma, COPD, cardiovascular disease, or diabetes.
How H3N2 Differs From COVID-19 And The Common Cold
Though all three are viral infections, H3N2 flu differs from COVID-19 and the common cold. Here's how:
- Virus type: H3N2 is an influenza A virus. COVID-19 is caused by the SARS-CoV-2 coronavirus. The common cold is usually triggered by rhinoviruses or adenoviruses.
- Onset of symptoms: H3N2 tends to have a sudden onset, often appearing 1-4 days after exposure. COVID-19 symptoms may take 2-5 days, sometimes longer. The common cold is usually gradual, with symptoms building up slowly.
- Typical symptoms: H3N2 often presents with sudden fever, chills, severe body ache, cough, headache, sore throat and weakness. COVID-19 shares some of these but often includes loss of taste or smell and can cause more severe breathing difficulty. The common cold usually involves sneezing, runny nose and mild sore throat without high fever.
- Duration: H3N2 symptoms usually last 5-10 days, though cough and fatigue may linger. COVID-19 has a wider range, with some recovering quickly and others experiencing long-term symptoms. A common cold typically resolves within 3-5 days.
- Severity: H3N2 can lead to complications such as pneumonia or worsening of chronic conditions, particularly in vulnerable groups. COVID-19 can affect multiple organs and sometimes cause long COVID. The common cold is generally mild and less risky.
Symptoms To Look Out For
Here are a few symptoms of H3N2 flu that you should beware of:
- Sudden high fever (often above 38-39C), chills
- Persistent cough and sore throat
- Severe fatigue, weakness and body aches
- Headache and nasal congestion
- In children: sometimes nausea, vomiting or diarrhoea
- Many patients in this outbreak report fever lasting more than 5-7 days, with cough lingering even after other symptoms improve
- Warning signs that need urgent medical attention include difficulty breathing, chest pain, bluish lips or face, confusion, or inability to keep fluids down
Consider the seasonal influenza vaccine, which often includes protection against H3N2 strains
Photo Credit: Pexels
Preventive Steps You Can Take
Like in the case of all viral infections, preventing H3N2 flu involves the following steps that should be strictly followed:
- Wash hands regularly with soap and water for at least 20 seconds
- Wear masks in crowded or poorly ventilated places
- Cover your mouth and nose when coughing or sneezing, and discard tissues immediately
- Avoid close contact with sick people; if someone at home is ill, try to isolate them
- Keep living spaces well-ventilated to reduce viral spread
- Maintain good nutrition, hydration and rest to support immunity
- Consider the seasonal influenza vaccine, which often includes protection against H3N2 strains. This is especially important for children, the elderly and those with chronic illnesses
When To See A Doctor And Available Treatments
You should consult a doctor if:
- High fever continues beyond 3-4 days
- You experience breathing difficulties, chest pain, or worsening cough
- Symptoms do not improve with rest and basic medicines
- You cannot keep food or fluids down
- You belong to a high-risk group such as older adults, pregnant women, children, or those with underlying chronic illnesses
Treatment options include:
- Prescription antivirals such as oseltamivir (effective if started early)
- Fever reducers and pain relievers such as paracetamol
- Cough medicines (expectorants or suppressants, as advised by a doctor)
- Rest, fluids and nutrition at home for most mild to moderate cases
- Hospitalisation and oxygen support in severe cases or complications
Home care tips:
- Stay isolated in a separate room if possible
- Use steam inhalation or humidifiers for congestion
- Keep utensils, bedding and towels separate for the sick person
- Regularly clean frequently touched surfaces
The ongoing surge of viral illnesses in Delhi-NCR, driven largely by H3N2 influenza A, is a wake-up call. With nearly 7 out of 10 households affected, preventive action, early medical consultation and responsible care are essential. While most people may recover with rest, those at higher risk must be especially vigilant. Staying informed, taking precautions and acting early remain our strongest shields against this seasonal threat.
Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.
