A novel coronavirus (nCoV) was identified, at the end of 2019, as the cause of a cluster of pneumonia cases in Wuhan, a city in Hubei Province of China. It then rapidly spread, resulting in an epidemic throughout China, followed by an increasing number of cases in other countries across the world. In February 2020, the World Health Organization (WHO) also designated coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
On February 19, the first official report of the cases with COVID-19 in the city of Qom, Iran, was correspondingly released. As of September 25, 2020, the COVID-19 outbreak has infected at least 32 million people worldwide. Concurrently, according to the WHO statistics, over 435,000 cases and the death toll exceeding 25,000 people has been so far reported in Iran. Based on the report by Shiraz University of Medical Sciences, Shiraz, Iran, COVID-19 cases in Fars Province, Iran, had surpassed 50,000 people as of September 20, 2020, while the mortality rate from this fast-spreading disease had crossed 940 patients.
To this point, the disease manifestations have varied from asymptomatic infection to severe fulminant pneumonia, respiratory failure, and death; however, the proportion of severe or fatal infections may also show a discrepancy by location. Such estimates are rapidly changing as more data are becoming available. With reference to the most recent WHO COVID-19 Situation Report, the global mortality rate is 5.3% [1].
The incubation period for COVID-19 is generally within 14 days following exposure, with most cases occurring approximately four to five days after being infected [2–4]. The proportions of asymptomatic infections have not been thus far investigated in a systematic and prospective manner. As estimated in the literature review, it is as high as 30–40% [5, 6].
The spectrum of symptomatic infections range from mild to critical and most infections are not severe [2, 7, 8]. Pneumonia seems to be the most frequent serious manifestation of this infection, primarily characterized by fever, cough, dyspnea, and bilateral infiltrates on chest imaging tests [8–10]. However, other features including upper respiratory tract infection (URTI) symptoms, myalgia, diarrhea, and loss of smell or taste are common. There are no specific clinical characteristics that can reliably distinguish COVID-19 from other viral respiratory infections, although development of dyspnea several days after the onset of initial symptoms is suggestive [4, 11]. Reviewing the complications, acute respiratory distress syndrome (ARDS) is assumed as the major complication in patients with the severe type of the disease and can manifest shortly after the onset of dyspnea. Furthermore, other side effects can be arrhythmias, acute cardiac injury, thromboembolic complications, and shock [3, 10, 12–14].
Comorbidities and other conditions, introduced to be associated with the severe cases of the disease and mortality are various. The severe condition can accordingly occur in healthy individuals of any age, but it is predominantly observed in older adults or those with underlying medical comorbidities such as cardiovascular diseases (CVDs), diabetes mellitus (DM), hypertension (HTN), chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), types of cancer, obesity, and smoking [11, 15–19].
As well, DM and poor glycemic control are regarded as major risk factors of infections especially influenza and pneumonia. In addition, studies on patients with DM have found that viral respiratory infections possibly cause a more severe type of the disease compared with non-diabetic cases [20]. Indeed, DM has been widely investigated in previous epidemics and pandemics such as influenza A virus subtype H1N1 (A/H1N1), SARS, and Middle East respiratory syndrome-related coronavirus (MER-SCoV), and it has been further identified as an important risk factor for mortality and morbidity [21–23].
There are some data regarding the association between DM and COVID-19, supporting that DM should be taken into account as a major risk factor for rapid progression and poor prognosis of COVID-19 [20, 24]. They also demonstrate a significant association between DM status and higher mortality rate in diabetic patients with COVID-19 [17] and indicate that glycemia is associated with markedly improved outcomes in patients with COVID-19 and pre-existing DM if it is well-controlled [25], but there is still considerable ambiguity with regard to diabetic patients with COVID-19 (29, 30)
This study aimed to explore whether DM was a risk factor influencing presentation, progression, and prognosis of COVID-19 or not. Accordingly, a total number of 447 COVID-19 patients admitted to Aliasghar Hospital and Chamran Hospital, and dedicated to COVID management and affiliated to Shiraz University of Medical Sciences, in the city of Shiraz, south-central Iran, from February 20 to April 29, 2020, was included to evaluate risk factors, comorbidities, and probable associated factors with this disease.