After swine flu, H3N2 spreads its tentacles

PUNE: Another strain of influenza A virus, besides H1N1 (swine flu), is making its presence felt in the city and its adjoining areas, laying sizable number of people down with flu-like symptoms.




The subtype, H3N2, just like swine flu is characterized by fever, cough, sore throat and weakness. “Positivity of both these virus types has collectively gone up to 5-10% in the last few days,” scientists at the Pune-based National Institute of Virology (NIV) said.

“The co-circulation of both these virus types, H1N1 and H3N2, is one of the reasons why we are seeing more cases of influenza-like illness these days. The H3N2 virus is co-circulating not only in Pune and Pimpri Chinchwad, but also in other parts of the state,” senior NIV scientist Mandeep Chadha told TOI.

The scientist said H3N2, just like swine flu, causes mild to moderately severe illness in most cases. “But there is no need to panic. Having said that, people with comorbid condition should be more cautious and should not delay in seeking treatment,” Chadha said.

“Swine flu and H3N2 are subtypes of influenza A virus. They cause flu-like symptoms like fever, cough, sore throat and weakness. Patients infected with H3N2 virus go unreported as this subtype is not tested at private labs the way some pathology labs have started testing throat swab samples of suspected patients of swine flu,” the scientist added.

Chadha said seasonal spike in influenza cases, including swine flu, is a known phenomenon. “There is nothing unusual about it. It is only the level of transmission of this virus that differs. Besides, all influenza viruses are known for their rather unpredictable behaviour. We have seen swine flu cases even during summer,” she added.

Although swine flu has become endemic and is like any other seasonal influenza strain now, NIV scientists still monitor its genetic make-up to rule out the virus developing extreme virulence.

“However, there is no such thing now. It continues to be the Michigan strain of swine flu virus, which has been in circulation since last year,” Chadha said.

The observations of general practitioners in the city corroborate the NIV scientists’ findings. “There is perceptible rise in the number of cases of influenza-like illness in the city. I have been seeing the cases with flu-like symptoms in all age groups,” senior general practitioner Prakash Mahajan said.

General practitioner Mahesh Wayal said, “I am seeing three to four patients every day with swine flu-like symptoms. These patients are mostly in the age group of 22-38 years.”

But how suspected patients of swine flu differ from patients with common flu or respiratory tract infection?

Usually, in cases of common respiratory infection, patient has cold, cough, redness in the eyes, runny nose in the first three days after the onset of the illness. The person can develop lower respiratory tract infection, including chest congestion, with expectoration in normal course on the fourth or the fifth day. But this progression of illness is very fast among swine flu suspected patients. They progress to lower respiratory tract infection, including chest congestion, and mild breathlessness within 36 hours of the onset of illness,” Wayal said.

In most of these patients, where progression of flu-like symptoms is quick, the virus responsible could be influenza A H3N2, the NIV scientist said.