An attack of shingles can increase the risk of having a stroke or heart attack years later, new research suggests.
For people under the age of 40, the viral infection boosted the chances of a stroke by 74% and a heart attack by 50%.
Older individuals were less affected, but shingles increased their risk of a heart attack by 10% and of a "mini-stroke" or transient ischaemic attack (TIA) by 15%.
Researchers studied data on 106,000 patients with shingles and 213,200 matched non-sufferers. Patient records were reviewed for an average of six years after a shingles diagnosis and in some cases for as long as 24 years.
A total of 40 people with shingles went on to experience a stroke, compared with 45 of those who did not have shingles.
People under 40 affected by shingles were more than twice as likely to have a TIA.
Shingles is caused by the same virus responsible for chicken pox, which can lie dormant in nerve roots for years before awakening and producing a painful rash.
Stress and inflammation may explain the link between shingles and stroke, scientists believe.
Study author Dr Judith Breuer, from University College London, said: "Anyone with shingles, and especially younger people, should be screened for stroke risk factors.
"The shingles vaccine has been shown to reduce the number of cases of shingles by about 50%. Studies are needed to determine whether vaccination can also reduce the incidence of stroke and heart attack.
"However, what is also clear is that factors that increase the risk of stroke also increase the risk of shingles, so we do not know if vaccinating people can reduce the risk of stroke per se. Current recommendations are that anyone 60 years and older should be vaccinated. The role for vaccination in younger individuals with vascular risk factors needs to be determined."
The findings are published in the online issue of the journal Neurology.