Public health officials said Friday they were investigating the first suspected death from measles in Britain in five years, after an outbreak blamed on a campaign against vaccinations.
More than 800 people have contracted the highly contagious disease in Wales in the past six weeks, centred around the southern city of Swansea, in the worst outbreak for years.
Marion Lyons, director of health protection for Wales, said tests were being carried out on the first suspected fatal case. If confirmed, it would be the first in Britain since 2008.
"A diagnosis of measles has not yet been confirmed. Testing the deceased for measles is forming part of the investigations being overseen by the coroner," she said.
"My sympathies are with the family at such a tragic time. Whatever the cause of death in this case, we should not be surprised if, as the outbreak grows, we start to see deaths in Wales."
Since early March, more than 800 cases of measles have been confirmed in Wales, compared to just 116 in the whole of 2012 and only eight between 1996 and 2002, official data shows.
The age group most affected is children aged 10 to 14.
The outbreak has been linked to the low uptake of the combined Measles Mumps and Rubella (MMR) vaccination, which is widely used across the world as the most effective prevention against measles.
Immunisations across Britain fell in the late 1990s following the publication of research suggesting the MMR was linked to an increased risk of autism and bowel disorders.
Andrew Wakefield's 1998 study caused public outcry, and although his claims have been comprehensively proven to be wrong, health officials have struggled to restore public confidence in the jab.
The outbreak of measles in Wales sparked queues outside clinics as parents rushed to get their children immunised, while special vaccination sessions are also taking place in schools.
The disease causes a distinctive red-brown rash on the skin, fever, cold-like symptoms and fatigue.
It can cause serious complications in around one in 15 cases, leading to deafness, brain damage and even death.
However, two doses of the MMR vaccine offer almost guaranteed protection against the disease. Vaccination levels in Britain are now at a high of around 88 percent, officials say.