Friday, 21 October 2011 20:45
2011 has seen a considerable increase in reported measles cases in Canada and the USA - the vast majority of people who became ill were not vaccinated, informs James M. Hughes, MD, President of the Infectious Disease Society of America. Measles had been declared 'eliminated' in the USA thanks to a high rate of MMR (measles, mumps and rubella) vaccinations among infants.
"Eliminated" means a disease has not been spreading continuously - which in this case meant since 2000.
However, when measles comes in from abroad, outbreaks can occur, mainly through unvaccinated Americans who travel abroad to Europe or other parts of the world, come back and infect others, most of whom are also unvaccinated. Infected foreign tourists coming into the USA are also a source of infection for unvaccinated Americans in the USA.
Measles, one of the most contagious diseases there are, can spread rapidly in a community where vaccination rates are low, or where vaccination rates are not complete (people have not had all their shots). The current measles outbreak is the largest in the US for 16 years and 16 years in Canada.
So far this year, in the USA there have been 212 reported cases of measles, of which 68 have been admitted to hospital; at least twelve of them had developed pneumonia, says the CDC (Centers for Disease Control and Prevention).
86% of infected individuals this year were unvaccinated. 27 cases involved infants less than twelve months old.
In 47% of imported cases a US resident was returning from Europe. In some parts of Europe vaccination rates are much lower than in the USA and there is a serious ongoing measles outbreak.
Health authorities say prompt public health response efforts have stemmed the spread of the outbreak.
Infectious Disease Society of America president, James M. Hughes, said:
"Forest fires start with sparks, but unless there is sufficient dry tinder, they won't roar out of control. The same is true of outbreaks. The occasional case is not an issue, but when it occurs in a community where a fair number of people are not vaccinated it can cause serious problems. This is why vaccination is important. We don't want to return to the days when measles and other vaccination-preventable diseases were rampant."
Measles vaccinations became available in the 1960s. Before they did, approximately three to four million individuals were infected annually, 48,000 were admitted to hospital, 1,000 developed lifelong disabilities, and 500 died
Huong McLean, PhD, epidemiologist at the CDC, Atlanta, Georgia, said:
"The MMR vaccine is very safe and effective at preventing measles, and high coverage is critical for preventing outbreaks. Quick public health response limited the spread of the disease. But the more unvaccinated people there are in a community, the more difficult it is to control an outbreak."
The financial burden of a small measles outbreak
A measles outbreak earlier this year in Salt Lake County, Utah occurred when a local unvaccinated high school pupil returned from Europe with measles. The disease only spread to nine other people because local authorities responded rapidly. However, infection control measures carried out by two local hospitals, state and local health departments cost $300,000.
When an infected student or adult goes to school, every person there is exposed. According to Utah law, anybody who has been exposed to measles and has not been vaccinated or cannot prove they have been vaccinated has to stay at home (quatantined) for 21 days after being exposed. In this case 12,000 were told about possible exposure and 184 had to be quarantined, including 51 schoolchildren. The costs quoted did not include other actions, such as hiring substitute teachers.
Karyn Leniek, MD, MPH, deputy state epidemiologist for the Utah Department of Health, Salt Lake City, said:
"It is always a concern to have a large number of unvaccinated people in close proximity. Our goal is to have as many people vaccinated as possible to protect those who cannot receive the vaccine and who are not fully immunized."
Written by Christian Nordqvist