Nicholson Bailey model (NB-1930) [7]. In this paper the modified NB model is applied to host parasitoid system and the stability criteria were analysed and illustrated.

Introduction: Corona virus disease-19 (COVID-19), produced by severe acute respiratory syndrome Corona virus 2 (SARS-CoV2), has become a global pandemic, giving rise to a serious health threat globally. In India we have seen a two wave pattern of reported cases with peak of rst wave in September 2020 and peak of second wave in May 2021.Women undergoing pregnancy and those at the time of child birth and puerperium constitute potentially vulnerable populations for covid-19. Aims And Objectives: To evaluate differences in clinical presentation, co-morbidities, pregnancy complications and outcomes in women with covid-19 during rst wave and second wave of covid-19 pandemic. Materials And Methods: We conducted a retrospective observational cohort study of all hospitalized pregnant and postpartum woman with SARS-CoV2 infection in Government General Hospital, Kurnool. All the patients admitted from 1st May to 31st October 2020 were considered to be in the rst wave and those admitted from 1st April to 31st June were considered to be in second wave. Results: Incidence of cases has increased from 14.18 to 16.8%.There was two fold increase in the symptomatic cases from 4.2 to 8%patients in the second wave were younger in the age group of 16-25yrs.The number of pregnant women delivered by Caesarean section have increased from 57.5 %to 61.1 %.ICU admissions have signicantly increased from 2.7% to 3.1% Case fatality rate has increased from 0.4%-1.1%. As observed from the above results there is higher frequency of severe Covid 19,increased ICU ad Conclusion: missions and maternal deaths in second wave of Covid 19 pandemic as compared to the rst wave .Although the exact causes of increase in severity and mortality are unknown ,but probably due to emergence of most pathological strains of SARS-Co2.