Keshan disease is a rare form of heart disease caused primarily by severe selenium deficiency. First identified in 1935 in Keshan County in northeastern China, it damages heart muscle tissue, leading to an enlarged, weakened heart that can progress to heart failure. The disease occurs almost exclusively in rural regions of China where the soil contains very little selenium, a trace mineral essential for protecting cells from damage.
How Selenium Deficiency Damages the Heart
Selenium is a building block for specialized proteins your body uses to neutralize harmful molecules called free radicals. Two of these proteins are particularly important for heart health. When selenium intake drops low enough, production of these protective proteins falls, and oxidative damage accumulates in heart muscle cells. Studies comparing heart tissue from people with Keshan disease to healthy controls found significantly lower levels of these protective proteins in affected individuals.
Over time, this unchecked damage kills patches of heart muscle (a process called myocardial necrosis) and replaces them with scar tissue. The heart enlarges to compensate, its pumping weakens, and irregular heartbeats develop. The end result looks very similar to dilated cardiomyopathy, a more common condition where the heart becomes stretched and floppy. That resemblance makes early-stage Keshan disease difficult to distinguish from other forms of heart muscle disease.
The Virus Connection
Selenium deficiency alone doesn’t fully explain the disease. Researchers have long suspected that a common virus, coxsackievirus B3, acts as a second trigger. This virus is widespread and usually causes only mild illness in well-nourished people. But in a selenium-deficient body, two things go wrong. First, the immune system is weaker, giving the virus freer rein. Second, the virus itself can mutate into a more dangerous form.
In selenium-deficient mice, coxsackievirus B3 accumulates mutations at an accelerated rate because the body lacks the antioxidant defenses that normally limit damage to viral genetic material. A normally harmless strain can transform into one that directly attacks heart tissue. This dual mechanism, selenium deficiency plus viral mutation, helps explain why the disease appears in seasonal outbreaks (peaking in cold winters in northern China and hot summers in the southwest) rather than striking everyone in a low-selenium area equally. A combined deficiency of selenium and vitamin E in the diet may further raise vulnerability during these seasonal infection waves.
That said, the viral theory isn’t fully settled. Enterovirus genetic material has been found at high rates in the heart tissue of Keshan disease patients, but it also appears in people without heart damage, leaving some questions about exactly how much the virus contributes versus selenium deficiency alone.
Who Gets It and Where
Keshan disease has been documented in 330 counties across 16 provinces in mainland China, a geographic footprint that closely overlaps with a well-mapped belt of selenium-poor soil stretching across the country. The World Health Organization classifies it under dietary selenium deficiency (ICD-10 code E59). Adults in the hardest-hit areas historically consumed no more than 10 micrograms of selenium per day, far below the intake of at least 20 micrograms needed to prevent the disease.
The disease disproportionately affects two groups: children between ages 2 and 10 and women of childbearing age. Both populations have higher nutritional demands relative to their intake, making them more vulnerable when the food supply is selenium-poor. A 2015-2016 survey of roughly 237,000 people across 280 endemic counties found that disease prevalence clustered in the provinces of Shaanxi, Gansu, Shanxi, Inner Mongolia, and Jilin. Notably, prevalence was closely tied to poverty: counties with lower per capita disposable income had significantly higher rates of the latent (early, symptom-free) form of the disease.
Symptoms and Forms
Keshan disease ranges from a silent, slowly progressing condition to a sudden cardiac emergency. In its latent form, the heart is already showing signs of enlargement and weakened pumping on imaging, but the person feels fine. This stage is the most common finding in modern surveys of endemic areas.
The chronic form develops gradually, with symptoms typical of heart failure: fatigue, shortness of breath during activity, and swelling in the legs or abdomen. Heart rhythm abnormalities are common. In the acute form, the onset is rapid. The heart’s pumping ability drops sharply enough to cause cardiogenic shock, a life-threatening state where the body’s organs aren’t getting enough blood. Before selenium supplementation programs, acute episodes were a leading cause of sudden death in affected communities, particularly among young children.
Prevention Through Selenium Supplementation
China launched large-scale selenium supplementation trials in endemic areas beginning in the 1970s, and the results were dramatic. Disease incidence plummeted over the following decades. A 2018 meta-analysis pooling 41 studies found that selenium supplements reduced the risk of Keshan disease by 86%. Supplementation also reversed some of the early heart changes in people with latent disease, halting progression before permanent damage set in.
Since 2013, China’s public health strategy has shifted from active prevention to an elimination and assessment phase. Most endemic counties are now part of a national surveillance system that monitors for new cases. The combination of selenium supplementation, improved nutrition from economic development, and broader food distribution networks (which bring selenium-rich foods from other regions) has made new cases increasingly rare. Still, the link between poverty and latent disease in recent surveys suggests that the most remote and economically disadvantaged communities remain at some residual risk.
Why It’s Hard to Diagnose
One of the persistent challenges with Keshan disease is that it looks nearly identical to other forms of cardiomyopathy on standard tests. An enlarged heart, reduced pumping function, and irregular rhythms on an EKG or echocardiogram could point to Keshan disease or to idiopathic dilated cardiomyopathy, a condition with no known cause. The key distinguishing factor is context: a patient living in or originating from a selenium-deficient region, combined with low blood selenium levels, points toward Keshan disease. Without that geographic and nutritional history, the diagnosis is easy to miss.