Type 1 diabetes is thought to be caused by genetic predisposition and possibly environmental influences, such as exposure to certain chemicals or pathogens. On Friday, doctors in Taiwan said they've established convincing evidence for a long-speculated environmental cause: enterovirus infection.

The possible link between enterovirus diseases — polio, Coxsackievirus A, Coxsackievirus B and echovirus — and Type 1 diabetes has been debated since 1969, but solid proof has been evasive. And even the doctors in the current study, published in the journal Diabetologia, don't spell out exactly how enterovirus causes Type 1 diabetes. But they say the trend has been becoming more clear with studies that showed, for example, that widespread onset of diabetes tends to follow a seasonal pattern, usually just after outbreaks of enterovirus.

Using data from Taiwan's national health insurance system, the authors looked at people who were diagnosed with Type 1 diabetes between 2000 and 2008 and then checked out who was also previously diagnosed with some form of enterovirus. They say the relationship is more than accidental. Type 1 diabetes patients were 48 percent more likely than not to have had enterovirus infection.

There's another piece of evidence that bolsters the connection. Finland and Sweden have high rates of Type 1 diabetes, but low rates of enterovirus, suggesting genes are the main factor in the high incidence in that region. But in other places, "such as Africa, Asia, South America," the doctors said in a press release, there is "a low but increasing incidence of Type 1 diabetes and high prevalence of enterovirus infection." This suggests "environmental factors like enterovirus infection" are playing a larger role in the growing rate.

"We believe that the marked escalation of the said incidence in recent decades can be largely attributed to the highly endemic spread of enterovirus infection in Taiwanese children," they wrote, "given that there has been little gene flow and genetic drift in such a short period." They argue that getting more children vaccinated for enterovirus would result in lower rates of diabetes.

Source: T. Li, et al. "Enterovirus infection is associated with an increased risk of childhood type 1 diabetes in Taiwan: a nationwide population-based cohort study." Diabetologia. 2014.