As the rate of vaccinations fall, measles cases are on the rise in the United States, and out of control in Europe. Measles is a highly contagious disease spread via the air and on surfaces. It can live outside the host for two hours, in which time it can infect those who are not immunized. Just being in a room where an infected person has been can result in infection. The chances of contracting the disease after exposure to the virus are very high. The fact that contagious persons appear perfectly well in the early stages of the disease exacerbates the problem.
As persons who are not immune to the measles virus travel from Europe to the United States (that includes US citizens on vacation in Europe), the number of cases increases, particularly in areas where vaccination rates have fallen below 90%, and herd immunity is less effective.
Herd immunity. Let’s review the concept. From Wikipedia:
Herd immunity (also called herd effect, community immunity, population immunity, or social immunity) is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, thereby providing a measure of protection for individuals who are not immune. In a population in which a large number of individuals are immune, chains of infection are likely to be disrupted, which stops or slows the spread of disease. The greater the proportion of individuals in a community who are immune, the smaller the probability that those who are not immune will come into contact with an infectious individual.
Individual immunity can be gained through recovering from a natural infection or through artificial means such as vaccination. Some individuals cannot become immune due to medical reasons [such as your very young grandchildren; minimum age for the MMR is 12 months]
and in this group herd immunity is an important method of protection. Once a certain threshold has been reached, herd immunity gradually eliminates a disease from a population. This elimination, if achieved worldwide, may result in the permanent reduction in the number of infections to zero, called eradication. This method was used for the eradication of smallpox in 1977 and for the regional elimination of other diseases. Herd immunity does not apply to all diseases, just those that are contagious, meaning that they can be transmitted from one individual to another. Tetanus, for example, is infectious but not contagious, so herd immunity does not apply.
Herd immunity is vulnerable to the free rider problem. Individuals who lack immunity, particularly those who choose not to vaccinate, free ride off the herd immunity created by those who are immune. As the number of free riders in a population increases, outbreaks of preventable diseases become more common and more severe due to loss of herd immunity. Individuals may choose to free ride for a variety of reasons, including the perceived ineffectiveness of a vaccine, believing that the risks associated with vaccines are greater than those associated with infection, mistrust of vaccines or public health officials, bandwagoning or groupthinking, social norms or peer pressure, and religious beliefs. Individuals are more likely to free ride if vaccination rates are high enough so as to convince a person that he or she may not need to be immune since a sufficient number of others already are.
There is also a common belief that measles is just a childhood disease, and not at all dangerous. The “I had measles, and I’m just fine.” is a common claim. To those people I can only say that while complications are fairly uncommon, when they do occur they can result in death and permanent disability.
Most otherwise healthy children recover from measles just fine, but about 30 percent of people with measles develop one or more complications.
Eight percent of children develop diarrhea (which can also appear earlier and less severely, as a symptom of the infection). Pneumonia occurs in 6 percent of measles cases and is the most common cause of death from measles complications in children.
Other, less common difficulties include hepatitis, myocarditis (inflammation of the heart), meningitis, encephalitis (inflammation of the brain), and – very rarely – other serious brain complications. Complications are more likely in children younger than 5 years old and adults 20 and older.
In pregnant women, measles can cause miscarriage, premature birth, or a low-birth-weight baby.
Before the measles vaccine was introduced, about 3 to 4 million people in the United States were infected with the disease each year. Of those, 48,000 were hospitalized, and 400 to 500 died. After the vaccine program began, the number of measles cases was reduced by 99 percent.
In this article in U.S. News, there is a list of the 25 counties in the U.S. that are at highest risk of a measles outbreak. Most are in metropolitan areas of our largest cities.
So far, the number of cases nationwide is below 1,000, although this is the worst outbreak in 20 years. In Europe it is much, much, worse. From the Daily Star U.K.:
The World Health Organisation said the rise in cases was “unprecedented” for a preventable disease.
They revealed they are rapidly ramping up their response to the outbreak, which has spread over two years, “based on the growing number of children and adults affected by and dying from the disease”.
WHO revealed today that, since the beginning of last year, more than 90% of countries across the continent have together reported over 100,000 measles cases and over 90 related deaths.
The WHO highlighted “the persistence of pockets of non-immunized or under-immunized individuals in many countries fuelling the continuing spread of measles.”
More than half a million UK children could be at risk of disease after missing crucial jab, children’s charity Unicef warned last month.