Why is swine flu surging in Maharashtra? What are the symptoms?

In the first 12 days of August, Maharashtra reported nearly 900 new cases of swine flu with 23 fatalities linked to the infection. This is almost a 162 per cent increase over the total swine flu cases and toll, 552 and 20 respectively, which the state had reported since the beginning of the year till July 31.
With the massive uptick in cases this month, the state has so far reported a total of 1,449 cases and 43 deaths, with Pune, Kolhapur and Nashik recording the most number of fatalities.
What is swine flu or H1N1?
The influenza viruses belong to the Orthomyxoviridae family. Of the four genera described, the influenza A virus is the one that infects humans most commonly. The virus has proteins called hemagglutinin (H) and neuraminidase (N), both of which help it infect cells in the human respiratory and gastrointestinal tract. There are at least 18 H subtypes and 11 N subtypes, and combinations of these are used to denote the type of strain. Swine flu — named as it was a reassortment of human, pig, and bird influenza viruses — is a type of influenza A virus. It has the H1 and N1 subtypes of these proteins and is hence called H1N1. It was responsible for a pandemic in the year 2009, and since then, H1N1, H3N2 and some Influenza B strains have been the predominant strains circulating worldwide.
Why is the state witnessing such a surge in cases this year?
The virus is known to peak during the monsoon. The surge this year could be a combination of three factors — first, this is the first monsoon since 2020 without lockdowns. Second, it is possible that COVID-19 has made people more aware and they are accessing healthcare earlier. Third, there is a widespread acceptance of getting nasopharyngeal swabs and better access to diagnostic test kits, leading to increased testing. However, it is possible that this is a genuine surge, and what we are witnessing is an exceptional year.
It has been witnessed that in alternative years, the state/Mumbai reports a large number of swine flu cases. What are the epidemiological reasons behind it?
Reassortment of viral proteins on the surface of the influenza virus can occur every few years. This can render exing immunity from past infections ineffective, as the virus evades the antibodies formed as a result of exposure to the earlier strains. Such “antigenic drifts” can cause year-to-year variability. Once every decade or so, larger changes in the virus (“antigenic shift”) can have the potential of causing a big spike. So, the creation of a new strain can have the same effects as the ancestral strain had on a native population.

How are the symptoms of COVID-19 different from swine flu? How can a person differentiate the symptoms?
Symptoms are similar and can be difficult to dinguish. Fever, nasal congestion, headache, sore throat, muscle aches and pains, cough are manifestations of both infections. Diarrhoea can also be seen in both. Secondary bacterial infections are possibly commoner in influenza than what we have witnessed in COVID-19 over the past two years. In the absence of having a documented close contact with someone who has influenza, it is impossible to dinguish between influenza and COVID-19, based on symptoms. Testing is the only way to confirm the infection.
What are the precautionary measures people should take?
Similar to COVID-19, influenza tends to cause the most severe disease among those with compromised immunity. These would include individuals who are elderly, those with immuno-suppressive conditions or on medication which suppress immunity, pregnant women, and those with comorbidities. Such individuals should especially avoid crowded spaces, closed, poorly ventilated areas and mask up especially when indoors. The annual influenza vaccine is protective, and those who have not received it this year should do so after consulting their doctor. Frequent hand-sanitising and isolating when sick are useful drills to protect oneself and close contacts. Oseltamivir, when started early, can potentially reduce the duration of illness and transmissibility, and would be recommended, especially for high-risk individuals.
What kind of patients are requiring hospitalisation?
Most individuals who have severe disease tend to be immuno-compromised. Influenza can often make individuals vulnerable to secondary bacterial infections after the initial viraemic phase and one needs antibiotics if there are indicators of a secondary infection. Viral respiratory infections are known to worsen underlying chronic diseases, and those with respiratory diseases such as COPD, asthma and underlying heart disease are especially vulnerable.