The current outbreak of enterovirus D68 has called attention to the wide range of problems viral infections can cause. In adults, the virus tends to have no effect at all. In children, it generally causes a cold-like illness, but sometimes triggers a severe respiratory infection or even partial paralysis.
Researchers also suspect that enterovirus infections may raise a child’s risk of type 1 diabetes.
A study published today in the journal of the European Association for the Study of Diabetes suggests that children who fall ill with an enterovirus infection are almost 50 percent more likely to be diagnosed with type 1 diabetes later in life. The finding is based on an analysis of the medical records of more than a million Taiwanese young people, half of whom were treated for enterovirus infections between 2000 and 2008.
Mysteries Remain About Type 1 Diabetes
Type 1 diabetes, also known as juvenile diabetes, has a strong genetic component, but genetics alone do not fully explain why some people develop the disease and others don’t. For instance, when one identical twin is diagnosed with type 1 diabetes, the second has just a 50 percent chance of following suit.
Genetics also can’t account for the growing number of type 1 diabetes cases in many parts of the world. That mystery has spurred research into which environmental triggers might also be at work.
Enteroviruses are one suspect, in part because they help account for another oddity about type 1 diabetes: it is more often diagnosed in the winter, a few months after enterovirus infections peak in the late summer and fall.
“Taiwan has relatively low type 1 diabetes incidence; we believe that the marked escalation of the incidence in recent decades can be largely attributed to the highly endemic spread of enterovirus infection in Taiwanese children, given that there has been little gene flow and genetic drift in such a short period,” the China Medical University researchers said in a press release.
Are Enteroviruses Just Innocent Bystanders?
The large sample size and strong correlation between enterovirus infections and type 1 diabetes are convincing. But the data don’t prove that viruses can trigger type 1 diabetes, said Jessica Dunne, director of discovery research at the Juvenile Diabetes Research Foundation (JDRF).
“We don’t know if there’s a separate cause, so we’re trying to understand those mechanisms through model systems and cadaverous organs” donated for research, she said.
Hypothetically, how could a virus cause diabetes? Scientists know that enterovirus infections can reach the pancreas. They propose that when the immune system attacks the virus, it may also destroy the cells that produce insulin. These cells, called beta cells, occupy nooks in the pancreas. In type 1 diabetes, the immune system destroys the body’s own beta cells, leaving it unable to process sugar.
But it’s also possible that there’s something about the pancreas of a child who is prone to type 1 diabetes that makes the organ more vulnerable to enterovirus infection. No one has yet shown that a viral infection occurs before the immune system begins to turn on the pancreas, Dunne noted.
Which comes first, the virus or the immune attack, is still unknown. But doctors increasingly agree that there is a link.
“Viruses are linked to destruction of the pancreatic beta cell in susceptible individuals,” said Dr. Michael Bergman, a clinical professor of endocrinology at New York University medical school.
EV-D68 Not the Most Obvious Suspect
Here’s the catch. Enterovirus D68 (EV-D68) is the strain of enterovirus currently making children across the United States sick. But there are at least 100 types of enterovirus.
The Taiwanese study didn’t break down the virus by strain, and only included patients who were sick enough to seek medical attention. Previous Scandinavian research on enteroviruses and type 1 diabetes has identified the Coxsackie B1 virus, which causes hand, foot, and mouth disease, as the chief suspect.
One way to solve the mystery is to develop vaccines for the suspected viruses.
“Our results suggest that preventive strategies, such as an effective vaccine against EV infection, may lessen the incidence of type 1 diabetes in Taiwan,” the researchers said.