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H3N2, causes and prevention
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H3N2, causes and prevention

Post by M Peerzada on Sunday, March 12, 2023

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Isolate in case of symptoms, don’t neglect worsening symptoms: Dr Salim Khan

Influenza viruses, which cause the infectious disease known as flu, are of four different types: A, B, C and D. Influenza A is further classified into different subtypes and one of them is the H3N2. According to the United States’ Centers for Disease Control and Prevention (CDC), H3N2 caused the 1968 flu pandemic that led to the death of around one million people globally and about 100,000 in the US. To understand the basics of H3N2,  Rising Kashmir’s Health Correspondent M Peerzada interviews Dr Salim Khan Professor, Head, Dept. of Community Medicine, GMC Srinagar.

What is H3N2?

Acute respiratory infections can be caused by bacteria and viruses. Viral infections are usually seasonal in nature and cause clustering of cases. These are usually caused by influenza viruses which have four main strains, viz. A, B, C and D.

Majority of influenza among humans occur due to Influenza-A viruses which are further divided into subtypes based on two proteins on the surface of the virus, viz, haemagglutinin (H) and neuraminidase (N). Based on these surface antigens, there are eleven H subtypes (H1 to H18) and eleven N subtypes (N1 to N11).

Nowadays, H3N2 subtype is circulating in various parts of the country and present with various respiratory and other constitutional and non-respiratory symptoms, which include cough, fever, headache, body-ache, sore-throat, stuffy nose or running nose and fatigue which could be exhaustive and tiresome. Some affected persons may present with nausea, vomiting and diarrhoea also.  However, H1N1, though lesser in number is also circulating and causing acute respiratory infection.

India is witnessing a sudden increase in patients having symptoms of cough, vomiting, sore throat, body ache and diarrhoea, are we seeing such cases in our hospitals in Srinagar?

Over last few days, the lab reports from Influenza labs are showing an increasing number of positive cases for H3N2. However, there is no substantial increase of hospital admission. But there is constant surveillance on the pattern of illnesses and their clinical spectrum.

As per the ICMR, H3N2 has resulted in more hospitalization than other flu subtypes. Why so?

As per Viral Research and Diagnostic Laboratories (VRDL) network of The Indian Council of Medical Research (ICMR) and Integrated Disease Surveillance Programme (IDSP), around half of Influenza-A positive cases detected have H3N2 subtype and this strain has shown to be more virulent, thus more severe infection (SARI) and subsequent hospitalization.

The currently available national data shows that around 92 percent affected cases suffer from high grade fever while severe cough is reported in about 86 percent.

Over one-fourth cases have breathlessness. Among severe acute respiratory infections (SARI) due to H3N2, around 16 percent have clinical features of pneumonia and equally present with wheezing chest. Around 10 percent of SARI due to H3N2 need oxygen and some need intensive care in hospitals.

What is the reason behind such an outbreak?

H3N2 is highly contagious and usually spreads from the affected person through droplets when he/ she talks, coughs or sneezes. It can even spread by touching the surfaces which have been contaminated with the H3N2 virus from the infected person and then touching mouth or nose with contaminated fingers or hand. Infected persons who do not follow respiratory hygiene (facemask, cough etiquettes) can transmit the infection to others in closed spaces and even contaminate the surfaces which are touched by vulnerable people.

Should such people avoid crowded places?

It is suggested that we should primarily avoid visiting crowded places which include markets, offices, family gatherings and in case of unavoidable situations, shall wear facemask, maintain hand hygiene and respiratory etiquette.

Remember how we dealt during COVID-19 times; same things apply for all other respiratory illnesses including H3N2 or H1N1 (seasonal flu/ influenza)

What are the symptoms to watch for as the symptoms are similar to other influenza viruses?

The symptoms are predominantly high-grade fever, severe cough, headache and body aches leading to exhaustion. Though symptoms may subside in few days or up to a week, but severe cough and body aches may remain for more duration, even up to three weeks.

It is the H3N2, and that is not Covid, what tests are recommended?

There is a network of Viral Research and Diagnostic Laboratories (VRDL) of ICMR and other labs under Integrated Disease Surveillance Programme (IDSP) across the country where real-time testing is done for various viral illnesses and thus it differentiates between various viruses including influenza virus and SARS COV-2

Who are the people at high risk of complications?

Even though viruses can affect any person, however, it affects more children and elderly people (below the age of 15 years or above 50 years of age). Persons with underlying co-morbidities like asthma, heart diseases, diabetes, weak immunity are more susceptible to infection and severity of the illnesses. Even people with various neurological or neurodevelopmental conditions are at a higher risk of contracting the disease.

Does it affect children?

Children are more vulnerable as they usually suffer from episodes of various illnesses during their childhood which weaken their immunity.

They prefer to stay and play together and have higher risk of disease transmission within themselves, especially in schools, creches and more so, they avoid to follow respiratory etiquette and avoid wearing facemasks.

What should one do if one is sick with the flu?

Usually flu is self-limiting illness and one recovers in a week’s time with symptomatic management of fever, cough, headache, body ache etc. As it is a viral infection, antibiotics which are meant for bacterial infections, have no role in its management. Ideally, a doctor’s consultation shall be sought and adhered to till full recovery. Antivirals have some role but shall be taken on doctor’s advice only and dispensed on doctor’s prescription only. It shall not be sold over-the-counter by pharmacies.

What precautionary measures should be taken?

As COVID-19 has taught us how to deal with an acute respiratory infection, same principles apply for other viral infections including influenza (H3N2 or H1N1) also.

Social distance, avoiding public gathering, wearing masks, cough etiquette, hand hygiene (using soap or sanitizers) shall prevent one from contracting infection. One shall avoid touching nose, mouth, and eyes.

Isolating oneself in case of symptoms. However, one should not neglect worsening symptoms and shall seek prompt medical attention for appropriate care.


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