Five States — Maharashtra, Gujarat, Rajasthan, Delhi, Tamil Nadu — account for about 70% of India’s confirmed COVID-19 cases, that on Monday stood at 46, 416.
However, data from the Health Ministry’s National Centre for Disease Control (NCDC), show that these are also States that consistently accounted for the bulk of swine flu cases, or seasonal influenza (H1N1) since 2015.
Also read: COVID-19 | State-wise tracker for coronavirus cases, deaths and testing rates
Last year, Rajasthan, Gujarat, Delhi and Maharashtra accounted for 15,580 cases of confirmed H1N1 — or 54 % of the confirmed infections. In 2018 again, Tamil Nadu, Maharashtra, Rajasthan and Gujarat, made up 65% of H1N1 cases.
In 2015, which saw 42,592 cases, the largest spike in cases since the swine flu pandemic of 2009-10, Maharashtra, Rajasthan, Gujarat and Delhi polled 63% of the cases .
Excluding 2016, Maharashtra and Gujarat have either led or been among the top three in India’s swine flu count.
The number of swine flu cases dipped to a 5-year-low of just 1,786 cases in 2016.
In 2010, that saw the swine flu dig its heels in India, Mahrashtra, with 6,814 cases, Delhi (2,725) and Karnataka ( 2,575) topped the list of infections.
Also read: COVID-19 | Interactive map of confirmed coronavirus cases in India
While both HIN1 and COVID-19 are due to pathogens that trace their origins to viruses from non-human hosts, they belong to different families.
While both infiltrate the lungs and cause characteristic pulmonary infections, they have varying lethality. Swine flu infections have a higher case fatality rates (deaths per confirmed cases) and can cause significant deaths in children as well as those less than 60. COVID-19 on the other hand relatively more dangerous to those above 60 and almost harmless in children. “It may be too early to say this because we are still in the middle of a pandemic but it is possible that Sars-CoV2 may replace H1N1,” Director, NCDC Sujeet Kumar Singh, told The Hindu. “But we’ve noticed this pattern (of high number of COVID and influenza cases) in Gujarat and Maharashtra.”
Also read: Full coverage of COVID-19 | The Hindu’s e-book on COVID-19 now available for download in multiple Indian languages
February-March are typical months for influenza in India. Most influenza activity in northern India was seen during the summer months, but in southern and western India, cases occurred mostly during winter months. In 2017, there was a summer and winter spike, the NMJ paper notes. Given the novelty of Sars-CoV2, scientists nowhere can rule out another spike later in the year. Infections in India, so far, are yet to peak.
Another scientist, who was among the authors of the NMJ paper told The Hindu that migration for work probably explained the relative dominance of Gujarat and Maharashtra in influenza and covid trends. “They are both respiratory viruses that spread through contact and often true numbers of such viruses are never detected. This year we are seeing an exceptional rise in testing and active surveillance across states. But in most years, it's only a few states that have the infrastructure and system that actively report cases,” AC Dhariwal, former director, NCDC told The Hindu. Maharashtra and Tamil Nadu have 50 testing laboratories each for covid 19 (many of which are also deployed for influenza).
While Uttar Pradesh and Bihar are among India's most populous states and see intense migration to other states for work, only in 2019 and 2017 did Uttar Pradesh feature among the top 5 in terms of swine flu burden. Except for 2015, when it recorded 352 cases, Bihar has never recorded more than 50 cases of swine flu.
This year too, the NCDC—as part of India's integrated disease surveillance programe—recorded swine flu cases. However no public records are available after Feb 23, until which India had already recorded 1,1132 swine flu cases.
