A new drug could pave the way to a measles pill that cures infections and stops them spreading.
In early tests, the drug ERDRP-0519 halted symptoms in infected ferrets and prevented their deaths.
The drug is administered by mouth, raising the prospect of turning it into an easy-to-take pill or capsule.
Scientists believe it could be used to curb measles outbreaks by treating people who have not yet developed symptoms but may have caught the virus from a friend, relative or other social contact.
A big advantage is that, while fighting the virus, the drug allows strong natural immunity to develop in those who are infected.
“The emergence of strong anti-viral immunity in treated animals is particularly encouraging, since it suggests that the drug may not only save an infected individual from disease, but contribute to closing measles immunity gaps in a population,” said US researcher Dr Richard Plemper, from Georgia State University.
Measles was virtually eradicated in the UK after the introduction of the MMR (measles, mumps, rubella) vaccine in 1988.
But in recent years it has made a comeback as a result of parents choosing not to vaccinate their children.
In 2012 there were more than 2000 cases of measles in England and Wales, the highest number in two decades.
Vaccination rates plummeted after now-discredited claims in 1998 of a link between the MMR vaccine and autism. Despite reassurances from health officials, MMR uptake reached its lowest level in 2003-04.
In the past five years, the proportion of children being immunised has fallen from 92 per cent to 87 per cent. Scientists say at least 95 per cent of children must be protected to be sure of keeping the infection at bay.
Measles, a member of the morbillivirus viral family, is highly infectious and in rare cases can be fatal. One in five children with measles suffer complications such as ear infections, vomiting, pneumonia and meningitis, and 10 per cent end up in hospital.
Currently, vaccination is the only weapon against measles available.
The new research, reported in the journal Science Translational Medicine, involved tube-feeding the drug to ferrets infected with canine distemper virus, another morbillivirus closely related to measles.
In ferrets, exposure to the virus is usually 100 per cent fatal. But the treated animals remained alive and symptom-free, and developed a strong immune response that prevented them being infected again.
The drug would not replace vaccination, but work alongside it, the scientists stressed.
They wrote: “We have pioneered the development of an orally available small molecule… that is capable of curing a lethal morbillivirus infection when administered at the first onset of viremia (viral spread in the blood).
“These findings may pioneer a path toward an effective morbillivirus therapy that could aid measles eradication by synergising with vaccination to close gaps in herd immunity due to vaccine refusal.”
Encouragingly, the study found that when the virus became resistant to the drug it was also weakened and less able to transmit between animals.