Respiratory viruses among ethnic Nicobarese during COVID-19 pandemic | BMC Infectious Diseases

Demographic and clinical characteristics

In this article, 428 patients with respiratory diseases were treated on an outpatient and inpatient basis at BJR Hospital, Car-Nicobar. Among 428 patients, 142 (33.2%) were hospitalized cases with severe acute respiratory illness (SARI) and 286 (66.8%) were OPD cases with ILI. (SG). Of 428 cases, respiratory samples were taken from 320 patients who were treated for laboratory tests for respiratory viruses. The median age of inpatients and outpatients was 37 years (IQR: 15 – 52 years). The median age of hospitalized cases was 51 years (IQR: 6.5 – 57.5 years), which is higher than the median age of outpatient cases of 34.5 years (IQR: 16 – 50, 5 years).

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

In children up to 5 years and patients aged ≥ 65 years, high frequency of cases observed in hospital (hospitalization) settings (24.1% and 15.5%) than in outpatient settings (9.4% and 6 .3%). The demographic characteristics of ILI in Car-Nicobar are shown in Table 1. Compared to pre-pandemic cases, the most frequent ILI cases were reported during the pandemic (59.9% vs. 40.1%). Among these 428 ILI cases, the most common symptoms were cough (78.47%), fever (53.83%), runny nose (40.67%) and shortness of breath (41.15%). ). All symptomatic distributions of SGs in Car-Nicobar have been presented in Fig. 1.

Fig. 1

Symptomatic distribution of flu syndrome in Car-Nicobar

Table 1 Demographic characteristics of ILI patients 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. Among these 88 positive respiratory cases, the most frequently identified were influenza A (H1N1) pdm09 (6%), influenza A (H3N2) (56%), human metapneumovirus (hMPV) (15%), human rhinovirus ( 12%), 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 %). The etiology of non-SARS respiratory virus CoV-2 infection in Car-Nicobar, India is shown in Fig. 2. Of these 88 respiratory positive cases, 16 were reported as hospitalized cases and the remaining 72 were reported as outpatient cases. Reported cases during the pandemic period have been reduced due to travel restrictions and changing care-seeking behavior. Additionally, being the only district hospital and with a 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 on an outpatient basis. Among outpatients, more cases were positive for influenza (H3N2) (68.1%) and rhinovirus (13.9%) while among hospitalized cases, the most frequent cases were hMPV (50%), influenza (H1N1) pdm 09 (18.8%) and RSV A (12.5%).

Figure 2
Figure 2

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

Age and sex distribution of respiratory viruses

Respiratory viruses are known to have age-specific prevalence. Therefore, to understand the age distribution of respiratory viruses for the entire age group, the groups have been divided into 0 to 5; 6 to 15; 16 to 25; 26 to 35; 36 to 45; 46 to 55; 56 to 65; ≥ 66 years old. The age groups 0-5 and 6-15 included children and adolescents respectively. Compared to other age groups, children up to the age of five were more frequently affected by viral respiratory infection (23.9%). Other commonly affected age groups were 6-15 years (21.6%), 16-25 years (18.2%), 46-70 years (17.0%) and 26-35 years (12.5%). Children up to five years of age were more frequently affected by hMPV (N = 7) and influenza A (H3N2) (N = 4). Among adults over the age of 46, influenza A(H3N2) (N=11) was most commonly reported. Reported viral respiratory infections in the 36-45 year age group were low (6.8%). In comparison with other respiratory viruses, influenza A(H3N2) reported in all age groups is particularly high in children, adolescents and the elderly. Among viral respiratory infections, men (57.9%) were more frequently affected than women (42.1%). Men were more frequently carriers of respiratory viruses, which were influenza A (H3N2) (56.9%) and rhinovirus (19.6%). In this study, the age groups were not significant with the cases of influenza-like illness (P > 0.05). The prevalence of respiratory virus by sex and age in Car-Nicobar is listed in Table.2.

Table 2 Prevalence of respiratory viruses by sex and age in Car-Nicobar, India

Respiratory viruses during the pandemic and pre-pandemic

Screening people with travel history and their contacts for SARS-CoV-2 was done by the administration with the help of local health departments. In the present study, suspected ILI specimens were covered throughout the study period, including before and during the pandemic. The initial report of the respiratory virus spreads among the Nicobarese tribe in Car Nicobar. Compared to the pre-pandemic period (June 2019 to July 2020), the number of respiratory viral infections other than SARS CoV-2 was more frequently observed during the pandemic (August 2020 to May 2021) in the month of December 2020 (N=14) and January 2021 (N=35). During the pre-pandemic period, respiratory viruses other than SARS CoV-2 were most commonly identified in September 2019 (N=9) and October 2019 (N=7). Suspected cases of respiratory illness were reported more frequently in January 2020 (N=32), March 2020 (N=26), and April 2020 (N=24). However, the number of respiratory viruses other than SARS CoV-2 identified was minimal at the time of the pre-pandemic period.

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

Figure 3
picture 3

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

Influenza A(H1N1) pdm 09 (N=5) was reported in 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. Non-SARS CoV-2 surveillance by month during pandemic and pre-pandemic in Car-Nicobar is shown in Fig. 4.

Figure 4
number 4

Distribution by month of non-SARS-Cov-2 respiratory viruses

Thus among 320 samples tested, 88 samples were identified with respiratory viruses. Of 88 positive cases, 61 cases identified during the COVID19 pandemic and influenza A(H3N2) 49 (80%) and rhinovirus 10 (16%) were primarily non-SARS CoV-2 respiratory viruses reported while in the period pre-pandemic 27 cases identified with respiratory viruses and human metapneumovirus 13 (48%) and influenza A (H1N1) pdm09 5 (18%) were the most commonly reported.

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