Demographic and Clinical characteristics

In this article, 428 patients with respiratory illness attended the outpatient and inpatient settings of BJR hospital, Car-Nicobar. Among 428 patients, 142 (33.2%) were hospitalised cases with severe acute respiratory illness (SARI) and 286 (66.8%) were OPD cases with Influenza like illness (ILI). Of 428 cases, respiratory samples were collected from 320 patients that were processed for laboratory testing of respiratory viruses. The median age of patients who attended both inpatient and outpatient settings was 37 years (IQR: 15 – 52 years). The median age of hospitalised cases was 51 years (IQR: 6.5 – 57.5 years) which is higher than the median age of outpatient cases 34.5 years (IQR: 16 – 50.5 years).

There was no significant gender-specific relation among ILI cases (P > 0.05)in the study. However compared with hospitalized cases, more frequent patients attended the outpatient settings. The percentage of males and females attending the outpatient settings werehigher when compared with hospitalized cases(male: 73.1% vs.26.9%) and (female: 60.7% vs. 39.3%) respectively.

Among childrenup to five years and elderly patients ≥ 65, high frequency of cases observed in hospitalised (inpatient) settings (24.1% and 15.5%) than outpatient settings (9.4% and 6.3%). Demographic characteristics of ILI in Car-Nicobar were shown in Table 1. Compared with pre-pandemic cases, most frequent ILI cases were reported during pandemic (59.9% vs. 40.1%). Among these 428 ILI cases, most common symptoms were cough (78.47%), fever (53.83%), runny nose (40.67%), and shortness of breath (41.15%). All symptomatic distribution of ILI in Car-Nicobar were shown in Fig. 1.

Fig. 1

Symptomatic distribution of Influenza-like illness in Car-Nicobar

Table 1 Demographic characteristics of patients with ILI in Car-Nicobar, India (2019 – 2021)

Detection of respiratory viruses

Among 320 suspected samples tested, 88 (27.5%) had viral respiratory infection confirmed by real-time RT-PCR. Of these 88 positive respiratory cases, most frequently identified were influenza A (H1N1) pdm09 (6%), influenza A (H3N2) (56%), Human metapneumovirus (hMPV) (15%), human rhinovirus (12%), human adenovirus(5%), respiratory syncytial virus A (2%), parainfluenza virus – 4 (PIV – 4) (1%) and human corona virus (HCoV–OC43 and HCoV – HKU1) (2% and 1%). Aetiology of non-SARS CoV-2 respiratory virus infection in Car-Nicobar, India are shown in Fig. 2. Of these 88 positive respiratory cases, 16 were reported as hospitalized cases and remaining 72 were reported as outpatient cases. The cases reporting during the pandemic period were reduced due the restricted movement and change in health seeking behaviour. Moreover being the only district hospital and with limited number of beds at BJR hospital, Car Nicobar Island only severe and complicated cases were admitted and the remaining cases were managed and treated as outpatients. Among the outpatients, more cases were positive for influenza (H3N2) (68.1%) and rhinovirus (13.9%) whereas among hospitalized cases, most frequent cases were hMPV (50%), influenza (H1N1) pdm 09 (18.8%), and RSV A (12.5%).

Fig. 2
figure 2

Spectrum of non SARS-Cov-2 respiratory viruses in Car Nicobar

Age and Gender distribution of respiratory viruses

The respiratory viruses are known to have age specific prevalence. Hence for understanding the age wise distribution of respiratory viruses for the overall age group, the groups were divided to 0 to 5; 6 to 15; 16 to 25; 26 to 35; 36 to 45; 46 to 55; 56 to 65; ≥ 66. The age groups 0 to 5 and 6 to 15 included the children and adolscent respectively. Compared with other age groups, children up to the age of five years were more frequently affected with respiratory viral infection (23.9%). Other frequently affected age groups were 6 to 15 years (21.6%), 16 to 25 years (18.2%), 46 to 70 years (17.0%) and 26 to 35 years (12.5%). Children up to the age five years were more frequently affected with hMPV (N = 7) and influenza A (H3N2) (N = 4). Amongadults aged above 46 years, influenza A (H3N2) (N = 11) were most commonly reported. Viral respiratory infections reported in the age group of 36 to 45 years were low (6.8%). Comparison with other respiratory viruses, influenza A (H3N2) reported in all age group especially high in children, adolescents and elder people. Among the respiratory viral infections, males (57.9%) were more frequently affected compared with females (42.1%). Males were more frequently harboured the respiratory viruses which were influenza A (H3N2) (56.9%), and rhinovirus (19.6%). In this study, age groups were not significant with the cases of Influenza-Like Illness (P > 0.05). Gender wise and age-wise prevalence of respiratory virus in Car-Nicobar are listed in Table.2.

Table 2 Gender and Age- wise prevalence of respiratory viruses in Car-Nicobar, India

Respiratory viruses during pandemic and pre-pandemic

The testing for SARS-CoV-2 from the people who had the travel history and their contacts was conducted by the Administration with help of local health services. In the present study, the samples of suspected ILI were covered during the entire study period, it includes before and during pandemic.The initial report on respiratory virus is diffusing among the Nicobarese tribe in Car Nicobar. Compared with pre-pandemic period (June 2019 to July 2020), number of non-SARS CoV-2 respiratory viral infection was more frequently noted during pandemic (August 2020 to May 2021) in the month of December 2020 (N = 14) and January 2021 (N = 35). During pre-pandemic, non- SARS CoV-2 respiratory viruses were most commonly identified in the month of September 2019 (N = 9) and October 2019 (N = 7). Suspected cases of respiratory illness were more frequently reported in January 2020 (N = 32), March 2020 (N = 26), and April 2020 (N = 24). However, the number of non- SARS CoV-2 respiratory viruses identified were minimal at the time of pre-pandemic period.

The total number of cases enrolled with respiratory illness and PCR proven respiratory viral infections during pre-pandemic and pandemic (COVID-19) are shown in Fig. 3. Human metapneumovirus (hMPV) (N = 13) and RSV A (N = 2) were the most commonly reported during September 2019 and October 2019. Rhinovirus appeared from January 2021 to April 2021 during the pandemic period, however, human adenovirus (N = 2) identified in March 2021 and April 2021.

Fig. 3
figure 3

Distribution of cases during pre-pandemic (June 2019–July 2020 and pandemic August 2020–May 2021

Influenza A(H1N1) pdm 09 (N = 5) was reported in the month of January 2020, February 2020 and April 2020. During the pandemic an upsurge of Influenza A (H3N2) (N = 49) was observed from December 2020 to January 2021. Month wise surveillance of non-SARS CoV-2 over the pandemic and pre-pandemic in Car-Nicobar are depicted in Fig. 4.

Fig. 4
figure 4

Month wise distribution-o-non SARS-Cov-2 respiratory viruses

Hence among 320 samples tested, 88 samples were identified with respiratory viruses. Out of 88 positives, 61 cases identified during the COVID19 pandemic and Influenza A (H3N2) 49 (80%) and rhinovirus 10 (16%) were predominantly reported non-SARS CoV-2 respiratory viruses while in the prepandemic period 27 cases identified with respiratory viruses and Human metapneumovirus 13 (48%) and influenza A (H1N1) pdm09 5 (18%) were most commonly reported.

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