Delhi H1N1 cases surge: Doctors explain rise, symptoms and who faces higher risk

Delhi has reported a sharp rise in H1N1 influenza cases this year, with 1,777 infections recorded up to August 20, compared with 229 during the corresponding period last year.

H1N1 has emerged as the dominant Influenza A subtype in the capital this year. Of the 2,392 Influenza A cases reported up to August 20, 1,777 were H1N1, while the total number of Influenza A and B infections stood at 2,602.

The rise has raised concerns about whether a new or more dangerous strain of the virus is circulating. However, the Indian Council of Medical Research (ICMR) has said there is no evidence of a new H1N1 strain and no reason for panic.

Doctors report rise in severe cases

Doctors across Delhi say they are seeing more influenza patients, with some developing pneumonia, respiratory distress and other complications.

Dr Animesh, Professor of Medicine at AIIMS Delhi, said influenza viruses undergo genetic changes over time, which can leave more people susceptible to circulating variants.

He said he was seeing around 15 to 20 influenza patients every day in his outpatient department. Some patients have developed pneumonia and respiratory distress, while others have reported diarrhoea and complications including kidney injury.

Doctors are also reporting secondary infections in some patients after the initial influenza illness.

No evidence of a new or more lethal strain

Dr Ashish Choudhary, Professor and In-charge of Virology at AIIMS Delhi, said the H1N1 virus currently circulating is not more lethal than previous seasonal variants.

The virus commonly known as pandemic H1N1 emerged during the 2009 swine flu pandemic and has since become a seasonal influenza virus. It continues to undergo minor genetic changes, a process known as antigenic drift.

Dr Choudhary said most infections remain mild, although patients with underlying illnesses are more vulnerable to severe disease.

At AIIMS, around 40 to 50 respiratory samples are being tested daily, with positivity rates varying between 5% and 15%, he said.

Pneumonia, oxygen requirement reported

Dr Rajesh Chawla, Senior Consultant in Respiratory and Critical Care Medicine at Indraprastha Apollo Hospitals, said the number of influenza cases has increased compared with last year.

He said some patients are requiring oxygen support and progressing to pneumonia. Gastrointestinal symptoms, including diarrhoea and, in some cases, blood in stools, have also been reported.

Doctors believe weather conditions and increased transmission may be contributing to the current surge.

Persistent cough and gastrointestinal symptoms

Dr Neha Rastogi, Senior Consultant in Infectious Diseases at Fortis Hospital, said doctors are seeing clusters of infections, with increased travel and greater testing also contributing to the rise in detected cases.

She said many patients are experiencing high fever during the first few days, followed by a persistent cough that takes longer to resolve.

Gastrointestinal symptoms such as diarrhoea and stomach cramps are also appearing alongside respiratory symptoms in some patients.

Who is at greater risk?

Doctors say severe influenza is more likely among:

• Older adults
• Young children
• People with lung or other chronic illnesses
• Patients with weakened immunity
• People with other underlying medical conditions

Dr GC Khilnani, Chairman of the PSRI Institute of Pulmonary, Critical Care and Sleep Medicine, said most severe cases being treated at his hospital involved patients with co-morbidities.

Do all patients need antivirals?

Doctors have cautioned that antiviral medicines are not required for every influenza patient.

Patients with mild illness generally recover without antiviral treatment. However, people at high risk of complications and those with severe disease may require antiviral therapy.

Oseltamivir is commonly used for influenza treatment, with doctors deciding whether it is appropriate based on the patient's condition. Antivirals work best when started early, particularly within the first 48 hours of symptom onset.

What should people do?

The current rise in H1N1 infections is significant, but doctors and ICMR have stressed that there is no evidence of a new pandemic strain.

People can reduce the risk of infection by maintaining hand hygiene, wearing masks in crowded settings and avoiding close contact with people who are unwell. Vaccination can also help protect against seasonal influenza.

People with underlying health conditions should seek medical attention promptly if they develop significant or worsening symptoms, particularly breathing difficulty, persistent high fever or signs of pneumonia.