**1. Introduction**

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> The COVID-19 global pandemic is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and continues into a second year [1]. In the Philippines, around ~552,000 cases have been recorded, ~11,500 (2%) of whom have died, as of 15 February 2021 [2]. HCWs remain at high risk of acquiring the infection as they attend hospitalized COVID-19 patients. In the months that followed the first confirmed case of COVID-19 in the Philippines, recorded in San Lazaro Hospital (SLH) [3], there has been an increasing national trend of confirmed cases. The influx of patients has placed an enormous workload on hospitals, and consequently to HCWs. Mandatory quarantine/isolation of HCWs suspected of exposure has strained hospital workforces; specifically, HCWs experiencing a high-risk exposure to a confirmed case, or presenting with influenza-like-illness (ILI), are required to undergo at least two weeks of quarantine/isolation away from the hospital. The resulting reduction in the HCW workforce causes extended work hours for

**Citation:** Agrupis, K.A.; Villanueva, A.M.G.; Sayo, A.R.; Lazaro, J.; Han, S.M.; Celis, A.C.; Suzuki, S.; Uichanco,A.C.; Sagurit, J.; Solante, R.; et al. If Not COVID-19 What Is It? Analysis of COVID-19 versus Common Respiratory Viruses among Symptomatic Health Care Workers in a Tertiary Infectious Disease Referral Hospital in Manila, Philippines. *Trop. Med. Infect. Dis.* **2021**, *6*, 39. https:// doi.org/10.3390/tropicalmed6010039

Received: 17 February 2021 Accepted: 12 March 2021 Published: 19 March 2021

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the remaining available staff, and inevitable "shift fatigue" [4] accompanied with increased fear and anxiety in working with COVID-19 patients.

We have reported that at SLH in Manila only 2% of HCWs were positive for SARs-CoV-2 as screened by RT-PCR (8 out of 324 HCWs screened) [5]. At that time, the criteria for screening were: (1) a history of close contact or high-risk exposure with a confirmed COVID-19 case or (2) the development of COVID-related signs and symptoms. Of the 324 HCWs, 88% had upper/lower respiratory tract infection-like (URTI/LRTI-like) illness such as fever, cough, sore throat, runny nose, shortness of breath, and loss of smell and taste. The small percentage of SARs-CoV-2 positivity suggests the possibility of underlying infections other than SARs-CoV-2.

SARS-CoV-2 is projected to circulate in the population indefinitely [6], and thus is likely to continue to cocirculate with common respiratory viruses. Although there is limited data on the prevalence of common respiratory viral infections in the Philippines, the Department of Health reports that acute respiratory infections consistently top the leading causes of morbidity in the country [7]. COVID-19 resides in the respiratory tract of the human host, and commonly exhibits URTI/LRTI-like symptoms, which overlap with those of common respiratory viral infections [8]. Because of the relatively small proportion of confirmed COVID-19 among HCWs described above [5], we sought to investigate whether HCWs who presented with these symptoms could be explained by other common respiratory viral etiologic agents.

#### **2. Materials and Methods**

HCW participants were tested for the presence of the following respiratory viruses: COVID-19, influenza A and B, human metapneumovirus (HMPV), respiratory syncytial virus (RSV), parainfluenza types 1 to 4, coronavirus 229E, coronavirus OC43, rhinovirus, adenovirus, and bocavirus.

Viral RNA from nasopharyngeal and oropharyngeal swab specimens were extracted using a QIAamp Viral RNA Mini Kit (Qiagen, Hilden, Germany), following the manufacturer's instructions [9]. Real-time PCR was performed to detect SARS-CoV-2 viral RNA using Corman et al. [10] and Nao et al. [11] protocols. Multiplex and hemi-nested multiplex PCR was done to test for the presence of the genetic materials from 13 other respiratory viruses, based on the protocol by Yoshida et al. [12]. Amplicons were visualized in 2% agarose gel.

We limited our analysis to those who exhibited URTI/LRTI-like symptoms. We categorized participants as "having URTI/LRTI-like symptoms" when they exhibited at least one of the following: fever, cough, sore throat, runny nose, shortness of breath, or loss of smell and taste. The epidemiological and clinical characteristics of these HCWs were compared between those who tested positive for the respiratory viral panels other than COVID-19 and those who tested negative for any of the panel of tests. The values were expressed as absolute numbers and percentages for categorical variables, and mean with standard deviation (SD) and median for continuous variables. Fisher's exact test and chi-square test were used to test for associations between categorical variables, and the Mann −Whitney test was used to compare discrete variables between classifications of categorical variables. A p-value of ≤0.05 was considered statistically significant. Stata SE ver. 16.1 (StataCorp 2019, College Station, TX, USA) was used for all analyses.
