Background Information on Measles
Introduction
Measles is an acute highly infectious viral illness transmitted via droplet infection. Almost all who are infected develop symptoms. Measles is a notifiable disease, which means that a doctor who sees a patient whom they suspect has measles is required by law to report it.
The Illness
A prodromal phase (early warning signs) of two to four days starts with fever, conjunctivitis, coryza and Koplik spots on the buccal mucosa (spots inside the mouth, in line with the molars). The characteristic rash appears on the body between the third to seventh day, spreads over four days and lasts for a week. Complications are common, and include otitis media, pneumonia, croup or diarrhoea. Other complications may include bronchiolitis, sinusitis, myocarditis, corneal ulceration, mesenteric adenitis (inflammation of the glands of the mesentery), hepatitis and thrombocytopaenic purpura (low blood platelets resulting in a haemorrhage into the skin). Severe complications of measles are encephalitis, and subacute sclerosing pan-encephalitis (SSPE), a rare but fatal late complication of measles infection.
The incubation period is about ten days with a further two to four days before the rash appears. However, it may be as long as 21 days and is prolonged in the immunosuppressed. Exposed individuals are highly infectious from the beginning of the prodromal period to four days after the appearance of the rash. Contagiousness is similar to chickenpox and more infectious than mumps or rubella.
Notification is based on clinical diagnosis.
Epidemiology
Measles is endemic in many countries. In 2005, 345,000 children died from measles globally according to WHO estimates, mostly in developing countries. Measles is also serious in industrialised countries. In the UK prior to 1988, half of all children who died from measles were previously healthy. There have been one death from acute measles in 13 years old child since 1992.
Case fatality rates for measles are age-related. They are high in children under one year of age, are lowest in children aged 1 to 9 years and then rise again with advancing age.
Measles Deaths E&W 1980 - 2006
Measles has been notifitable began in England and Wales since 1940, and notifications varied between 160,000 and 800,000, the peaks occurring in two-year cycles. The introduction of a single measles vaccine in 1968, had limited effect because coverage was never sufficiently high to have an effect on virus transmission. Measles notifications dropped until by the late 1980's, annual notifications had fallen to between just 50,000 and 100,000. In countries where high coverage was achieved shortly after the introduction of measles immunisation, the epidemic cycle was more effectively suppressed and very low levels of measles were observed.
Following the introduction of MMR vaccine in October 1988 and the achievement of coverage levels in excess of 90%, notifications of measles fell progressively to the lowest levels since records began. However, MMR vaccine covarage has been falling between 1995 and 2003. There have been several outbreaks of measles in communities with historically low vaccine uptake in 1998, 2002,2006 and 2007. Some of these outbreaks have spilt into pockets of the general population with low MMR coverage.
Diagnostics
Diagnosis of measles is usually done on oral fluid or serum. In acute cases measles virus can be detected in urine and throat swabs. Contact your local Health Protection Unit (HPU) for information and oral fluid sample test kit.
Treatment
There is no specific treatment for measles. Treatment should be based on symptoms. Human Normal Immunoglobulin (HNIG) is used to prevent an attack or reduce its severity, and is most effective if given within 72 hours.
For more information on the use of HNIG, see the PHLS Immunoglobulin Handbook
Prevention
Measles vaccine is one of the components of MMR vaccine. The introduction of MMR vaccine in 1988 effectively halted the two yearly cycles of measles epidemics. However, an epidemic of between 100,000 and 200,000 cases of measles during 1995, mostly in school children, was predicted in England and Wales based on epidemiological evidence from several sources. It was likely that the predicted epidemic would have caused substantial morbidity and mortality. The increasing proportion of susceptible individuals results from the reduced opportunity for unvaccinated children to acquire immunity through natural infection, following the sharp decline in circulation of measles after the introduction of MMR.
There are two licensed MMR vaccines: Priorix (SKB) using attenuated Schwarz measles strain and MMR II (Aventis Pasteur) using attenuated Enders line of the Edmonston strain. There is no single antigen measles vaccine licensed in the UK.
Recommended immunisation schedule
MMR is given in the national immunisation programme at 12-15 months and at 3-5 years of age. There is no upper age limit and where required, two doses can be given separated by a three monthly interval.
Frequently asked questions
Q: Why do we need two MMR vaccinations?
A: Experience has shown that one MMR vaccination protects over 90% of children who receive it, yet this is not enough to eradicate disease. If 90% of children have had MMR by their second birthday and only 90% of them were successfully protected, nearly 20% of all children would be left unprotected. Over the years, this would mount up until a measles epidemic would occur, as happened in the USA in 1989/90. By giving two doses this is prevented. Many countries follow a two-dose MMR policy.
Q: If we are giving the 2nd dose of MMR because 10% of children are not protected by the first, why not test all children's immunity through saliva testing, and then immunise those who need it?
A: Saliva testing determines acute infection and has not been validated to determine protection against disease. For more information, please see Statement from the PHLS Virology Committee.
Q: I am pregnant and my child has a rash. The GP says it is unlikely to be measles, what could it be?
A: Rubella, Parvovirus B19, varicella, human herpes virus 6 or a streptococcal rash are a few of the possibilities. For more information regarding the management of and exposure to rash illness in pregnancy,see:-
Guidance on the management of, and exposure to, rash iIlness in pregnancy.
Useful links
Last reviewed: 28 May 2008
