POST-RENASCENCE ENVIRONMENTAL ADAPTATION OF SWINE-ORIGIN INFLUENZA VIRUS (S-OIV).

Background The three types of influenza viruses are A, B, and C. They belong to the Orthomyxoviridae family of single stranded RNA viruses. Method Retrospective study was conducted on  7515 sample results data which were collected from January 2014 to December 2018 in the Department of Microbiology, Government Medical College, Kota Results 16.58% samples were positive over the period of study. Prevalence in 2014 was 3.08% followed by the drastic change in the number of cases in 2015 with the prevalence of 18.57% with the similar trend in the successive years except in 2016 which might be due to change in humidity. Post-renascence the virus was able to infect even at higher relative humidity. Discussion The dominant flu strain in India in 2017 was A/ Michigan/7/2009 (H1N1) pdm09 virus, replacing A/California/7/ 2009 (H1N1) pdm09 seen during 2016. The new strain is capable of infecting at relatively higher temperature.


Material and Method:-
Retrospective study was conducted on all the suspected cases of Influenza A H1N1 (Swine Flu) from January 2014 to December 2018 in the Department of Microbiology, Government Medical College, Kota, Rajasthan, India.
We have included all suspected swine flu cases in our study irrespective of their categories (A, B or C) and age group.
As per the laboratory criteria for diagnosis of influenza specimen suggested by WHO, the RT-PCR protocol was adopted. The throat swabs were collected under all aseptic and universal precautions and kept in Viral Transport Medium and processed in a Biosafety level Class II type B3 cabinet. Real-time Reverse Transcriptase Polymerase Chain Reaction (rtRT-PCR) was done as per the CDC Protocol using StepOne by Applied Biosystems(AB).
A total of 7515 sample results data was collected in the study. A specially designed data collection form was used to collect some epidemiological data like age, sex, and month of the test performance during study period.
Data of average temperature and humidity were collected from National Centre for Disease Control, Ministry of Health and Family Welfare last updated on 3 rd November,2019. 3 This is a retrospective analysis of routine laboratory work, so an ethical consideration was not necessary.

Results:-
A total of 7515 samples were obtained during the study period. Out of which 1246 samples (16.58%) were tested positive for swine flu influenza H1N1 (Table 1). Prevalence of swine flu positive cases was calculated for each year from 2014 to 2018 with its corresponding relative humidity and average temperature in our region.
With this data obtained we found out that the prevalence of swine flu positive cases in 2014 was 3.08% followed by the drastic change in the number of swine flu cases in the year 2015 with the prevalence of 18.57%. After renascence in the year 2015 the similar pattern was observed in 2017 and 2018 with an exception of the year 2016 (Table 2). With the pattern of humidity and its respective prevalence we have noted that after the renascence virus was able to infect even at higher relative humidity which was against the previous pattern that swine flu virus exhibits its infection only at low humidity (Table 3). With the data studied we found out that there was a trend of higher prevalence of swine flu positive cases in the months October to March in the year 2014, 2015 and 2016 which are broadly speaking considered as the cooler months as compared to the year 2017 and 2018 where the prevalence was higher in the months of relatively higher temperature i.e. April to September (Table 4).  Using the guinea pig as a model host, Lowen et al showed that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. 7 After the renascence of 2015, there has been a similar pattern of high virus activity observed except in the year 2016 in Rajasthan (197 cases) which might be due to the change in the relative humidity (Graph:1). This low prevalence in the year 2016 was also found in the Delhi (193 cases), Uttar Pradesh (122 cases), and Gujarat (411 cases). 8 with respect to the seasonal pattern of distribution of the disease, possibly linked with climatic conditions, seen during 2017. Understanding the genetic epidemiology of the virus in India would be helpful.

Conclusion:-
With our study we have tried to ascertain a relationship between the low prevalence in the year 2016 and the relatively higher humidity in that year. The cascade of swine flu infectivity is multi-factorial. The drastic change in the prevalence in the year 2017 and 2018 could be the ability of the virus to exhibit its infectivity even at different environmental conditions. For elaborative knowledge extensive researches must be carried out.