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Diabetes mellitus is an important global health issue leading to severe morbidity and mortality. The International Diabetes Federation has anticipated that the number of diabetic patients will increase to 380 million in 2025, and will finally increase to 439 million in 2030. Many studies have shown that diabetes mellitus has been linked with an increased risk of hospitalization with infectious diseases.

There are differences in innate immunity between diabetic and nondiabetic patients and also in adherence of microorganisms to diabetic and nondiabetic cells. These differences are important in the pathogenesis of increased prevalence of infections in diabetic patients. The monocytes of diabetic patients have impaired chemotaxis and phagocytosis. The presence of high glucose leads to a higher resting cytokine production by peripheral blood mononuclear cells (PBMCs); but after stimulation, this cytokine production is impaired as compared to the situation without glucose. Another substance which may play a role in the increased basal cytokine secretion is the advanced glycation end products (AGEs), which are products of glucose and lysine or arginine residues). An increased formation of AGEs takes place in poorly regulated diabetic patients.

A hyperglycemic environment can enhance the virulence of certain microorganisms, like Candida albicans. In vitro tests analyzing the functions of diabetic polymorphonuclear (PMN) cells show increased adherence of PMNs to bovine aortic endothelium. This increased adherence probably leads to a decrease in diapedesis and exudate formation of PMNs. A significantly lower chemotaxis has also been found in PMNs of diabetic patients (type 1 and type 2) compared to those of controls. Phagocytosis is also impaired in PMNs isolated from poorly regulated diabetic patients. Better regulation of diabetes leads to an improved phagocytic function.

Viral infections may be dangerous for people with diabetes because of problems with eating, insulin management, and hyperglycemia. The risk of complications from viral infections like influenza, increases in diabetics with associated increased risk of hospital admission, and intensive care admission. Viral infections like Hepatitis A and Hepatitis B are also more common among people with diabetes than in those without. Hepatitis C increases insulin resistance and the risk of developing diabetes.

Infections cause a stress response in the body, increasing the body’s production of glucose. This results in raised blood sugar levels, more so in diabetics since their mechanism for regulation of blood sugar levels are already compromised. The novel coronavirus may thrive in an environment of elevated blood glucose. The body of a diabetic is in a low-level state of inflammation, which makes the healing response of the body to any infection slower. High blood sugar levels combined with a persistent state of inflammation makes it much more difficult for people with diabetes to recover from illnesses such as COVID-19.

It has been seen that patients with DM are susceptible to developing infections with lower (but not upper) respiratory tract infections and urinary tract infections. One study showed that the age-standardized prevalence of total diabetes was 9.7% (10.6% among men and 8.8% among women), which was similar to the prevalence of DM in 2019-nCoV patients (COVID-19) and the overall prevalence of type 2 diabetes mellitus (9.1%).

Xiang Wang et al did a meta-analysis of 9 retrospective observational studies from all over the world, on COVID-19 patients with diabetes mellitus (DM). The diagnosis of 2019-nCoV was based on World Health Organization interim guidance (by RT-PCR). The pooled prevalence of DM in 2019-nCoV patients was 9% (total of 2007 cases). It was found that the prevalence of DM in patients with severe 2019-nCoV was 17% and the prevalence in patients with moderate 2019-nCoV was 7%. The prevalence of DM in severe patients with 2019-nCoV was significantly higher than that in moderate patients with 2019-nCoV.

Data from the National Health Service, England, showed that one in four people who died with COVID-19 also had diabetes. Earlier studies have also shown that about 25% of people who went to the hospital with severe COVID-19 infections had diabetes. It has been seen that patients with diabetes are not more likely to get the infection, but are more likely to have serious complications and die from SARS-CoV-2. Overall, having diabetes does put you at risk for COVID-19 complications, including the need for hospitalization and a ventilator.

In addition to developing the various complications of COVID-19, diabetic patients are also at greater risk for developing diabetic complications like diabetic ketoacidosis (DKA). A rise in blood pressure has also been seen in diabetic patients with COVID-19. High blood pressure can lead to dehydration. These patients should drink plenty of fluids and check their blood pressure very frequently regularly, about every six hours. If a person with diabetes has fever because of COVID-19, they are losing additional fluids. This can lead to dehydration, which may require intravenous fluids. As the blood sugar rises in response to the infection, the insulin requirements of the patient frequently rise. The blood sugar levels tend to fluctuate, as a result of which, frequent blood sugar monitoring is required and dosage of insulin is adjusted accordingly.

People with diabetes can protect themselves from contracting the virus by taking all the routine precautions and some that are specific for diabetics:

• Frequent hand washing with soap and water, for 20 seconds, or using an alcohol-based hand sanitizer when soap and water are not available.
• Avoid touching surfaces that have been touched by others.
• Frequently disinfect any potentially contaminated surfaces, such as countertops, tabletops, and door handles.
• The eyes, nose, or mouth should not be touched with unwashed hands.
• Practice physical distancing, by staying 6 feet (2 meters) away from others in public places.
• Cough and sneeze into the elbow (not the hands) or use tissues.
• Avoid contact with others who are sick, especially if they have a fever, cough, or both.
• Keep the immune system strong by getting at least 7 hours sleep per night and reducing stress levels as much as possible.
• Maintain an adequate intake of food and fluids.
• Keep a tight control of blood sugar.
• Limit the amount of time diabetics visit hospitals, to protect themselves and healthcare workers, and to reduce strain on the healthcare system.

References:

1. Xiang Wang, Shoujun Wang. Prevalence of Diabetes Mellitus in 2019 Novel Coronavirus: A Meta-Analysis. The Lancet. Posted: 31 Mar 2020.
2. King H, Rewers M. Global estimates for prevalence of diabetes mellitus and impaired glucose tolerance in adults. WHO Ad Hoc Diabetes Reporting Group. Diabetes Care 1993; 16 (1):157-177.
3. Benfield T, Jensen JS, Nordestgaard BG. Influence of diabetes and hyperglycaemia on infectious disease hospitalisation and outcome. Diabetologia 2007; 50 (3):549-554
4. Muller LM, Gorter KJ, Hak E, Goudzwaard WL, Schellevis FG, Hoepelman AI, et al. Increased risk of common infections in patients with type 1 and type 2 diabetes mellitus. Clin Infect Dis 2005; 41 (3):281-288.
5. Yang L, Shao J, Bian Y, Wu H, Shi L, Zeng L, et al. Prevalence of type 2 diabetes mellitus among inland residents in China (2000-2014): A meta-analysis. J Diabetes Investig 2016; 7 (6):845- 852.
6. Yang W, Lu J, Weng J, Jia W, Ji L, Xiao J, et al. Prevalence of diabetes among men and women in China. N Engl J Med 2010; 362 (12):1090-1101
7. Deresinski S. (1995) Infections in the diabetic patient: Strategies for the clinician. Infect. Dis. Rep.1, 1–12
8. Tater D. Tepaut B.Bercovici J.P.Youinou P. (1987) Polymorphonuclear cell derangements in type I diabetes. Horm. Metab. Res.19, 642–647.