A 2015-like swine flu outbreak might be on the anvil

A major outbreak can be inferred from its rapid spread towards the northern states which have not been highly affected by the virus in the past few years

By Akshit Sangomla
Published: Thursday 07 February 2019

Swine flu, caused by the H1N1 virus, is creating a scare in northern and western India since the beginning of 2019. Latest data indicates a major outbreak could be on the anvil. 

As of February 3, 2019, Rajasthan has recorded the highest number of cases (2,363) and deaths (85) due to the disease in the country according to data released by the National Centre for Disease Control. The number of cases is only 12 less than the state’s annual tally of 2,375 in 2018 which had resulted in 221 deaths that year.

While in 2015, there were around 42,592 cases in the entire year; in 2019, within a month, India has recorded about 6,701 cases of H1N1 and 226 deaths. The average monthly cases reported in 2015 was around 3,500, half of what it is this month. 

Delhi has recorded the second highest cases (1,011) till February 3 and the media has reported one death on February 6. The third most affected state in terms of reported cases and second in terms of reported deaths is Gujarat with 898 cases and 43 deaths.

Rajasthan and Gujarat together constituted half of the total cases and deaths in the country in the last month.

A major outbreak can also be inferred from its rapid spread towards the northern states which have not been highly affected by the virus in the past few years. For instance, Haryana has recorded 490 cases in just over a month this year, which is more than its annual tallies of any year since 2012.

Similarly, Himachal Pradesh has recorded 105 cases till February 3, and 14 of these patients have died. Compare this to the major swine flu outbreak in 2015 when the entire year saw 123 cases and 27 deaths in Himachal Pradesh.

The pattern also continues into Punjab, Jammu Kashmir and even Uttar Pradesh. In Punjab, 250 cases and 30 deaths were reported in the last month as compared to 47 cases and 11 deaths in 2018. In 2015 and 2017 the state had witnessed 300 and 295 cases in total respectively. 

Pooling the cases from the resurging virus in the newly affected states of Haryana, Jammu and Kashmir, Himachal Pradesh, Punjab and Uttar Pradesh constitutes almost one fifth of the total cases in the country.

Climate and local weather patterns might also be playing a role in the spread of swine flu. Experts in Maharashtra, in the past 9-10 years, have observed that the surge in influenza activity generally peaks twice in any year. The first spurt is seen in the post monsoon season and the second at the end of winter (January-February).

“In Maharashtra there were no deaths reported till July last year but as the monsoon withdrew and winter set in, the next few months saw an increased death rate and the state ended up with 461 deaths, the highest in the country in 2018,” Pradeep Awate,  Maharashtra’s head of epidemiology and infectious diseases expert, told Down to Earth.

Awate also observes that hot and humid weather discourages the spread of the H1N1 virus while cold and dry weather encourages it. He adds that while the link between cold weather and H1N1 has been scientifically established, more work needs to be done on the relationship between the virus and humidity.

He draws this conclusion from his lab’s observations of the distribution of cases within Maharashtra. While regions like Mumbai, Vidarbha and Nagpur which experience hot and humid conditions during the monsoon reported less number of cases, regions like Pune and Nashik which have cooler and drier weather during that period reported more cases.

“Even after available facilities and reporting biases are taken into account, we have observed that the monsoon patterns in certain areas affect the spread of the virus,” says Awate.

Another weather factor at play here is the difference between maximum and minimum temperatures at a place. When this difference is high it aids the spread of the virus and a low gap between these temperatures discourages the spread.

Awate attributes the recent spurt of H1N1 cases and deaths in northern and western India to the cold wave conditions that have prevailed this winter season. The lack of Western Disturbances in December could have also led to a lack of water vapour in the atmosphere paving the way for a cold and dry winter.

Down to Earth had earlier reported that as the weather becomes colder and drier, swine flu cases might rise. This link between cold weather and H1N1 has been observed even in Europe and the United States, according to Awate.

“Cold conditions in general lead to decreased wind speeds which let the infected virus droplet stagnate in the air, making its spread more conducive,” says Awate. The cold also leads to crowding of more people in small spaces which adds to the spread of the infection.

Apart from the weather conditions, a stronger strain of the virus (California instead of Michigan), decreased immunity among populations and migration of people from affected states to unaffected states might be important factors in the continuing spread of swine flu.

Higher unemployment rates in some of these states might induce further migration of people increasing the scope of the spread of swine flu to newer areas. These factors need to be studied in greater detail to understand the disease, curb its further spread and avert a major outbreak.

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