According to the Directorate-General of Health (DGS), of the 23 cases notified, 11 have been confirmed as measles by the Ricardo Jorge Institute and the other 12 are still being looked into.

Over the weekend media reports told of six cases of patients being admitted to hospital with measles in the Lisbon region, one of them an adolescent in serious condition who had to be transferred from Cascais, set of the capital, to the city's Hospital Dona Estefânia. According to the online edition of Expresso, the transfer was made to this hospital because it was the only unit “with rooms with negative pressure [ventilation] and intensive care necessary for this kind of situations".

The newspaper quoted the managing director of the hospital in Cascais where the patient had previously been as saying that she was one of six minors admitted to the unit with measles. The first was detected in a 13-month-old child who had not been vaccinated, and who was admitted to hospital on 27 March; she infected five hospital staff who, since they were vaccinated suffered the illness in only a mild form.

Measles is one of the most contagious of infectious diseases, and can cause serious illness or even death. It is avoidable for people who are vaccinated and has been under control for some years in Portugal.

More than 500 cases of measles have been reported this year alone in Europe, in at least seven countries, according to the World Health Organisation.

In several countries vaccination rates for children have fallen due to suspicions - that health authorities insist are unfounded - that vaccines can trigger problems such as autism.