Measles is a highly contagious infection of the respiratory system. Caused by the measles virus, a measles outbreak spreads when people breathe in infected droplets that are then exhaled through coughing or sneezing. The virus lives and flourishes in the mucus of the throat and nose of sufferers. A measles outbreak can also occur if someone touches a surface where infected droplets have landed and then inadvertently touches his mouth, eyes or nose. The virus can live on surfaces for several hours, which enables it to infect many new hosts as they come into contact with it.

A serious measles outbreak can occur in areas with large populations of unvaccinated people. Such was the case in 2010 in Malawi, where dozens of people died. More than 17,000 were infected. The outbreak was made worse by the victim's poor nutrition — people who lack adequate vitamin A appear to contract the virus easier than others — which left sufferers more susceptible to severe symptoms of the disease, including pneumonia, dehydration and blindness.

A measles outbreak also can happen in areas where a majority of people are vaccinated, simply by finding a weak link. An example of this is a 2008 measles outbreak in California in which a child's parents chose not to have him vaccinated against measles. The boy then traveled overseas, came in contact with the virus, and brought it home. Before anyone realized he had the virus, he had exposed hundreds of people, including several other children who had not been vaccinated and contracted the disease.

Prior to the development of a successful measles vaccine, approximately 130 million people a year contracted the virus. Despite the development of the vaccine and a significant decrease in infections, measles outbreaks still occur around the world and deaths are widespread. People traveling to undeveloped countries where measles is still quite common are encouraged to receive the appropriate vaccination to prevent a measles infection from occurring. As a person ages, the vaccine's effectiveness decreases and a booster may be needed.

Measles symptoms usually materialize approximately 10 days after coming into contact with the virus. Symptoms begin as a runny nose, elevated temperature and cough. Optical sensitivity to light occurs as the infection progresses, and the whites of the eyes also begin to appear red. After three to seven days, the symptoms become more severe and people suffer a higher temperature, which often reaches 105° F (40.5° Celsius). A red, blotchy rash appears over the infected person's body — even, possibly, on the palms of the hands and soles of the feet — and white spots may appear on the gums and elsewhere inside the mouth.

The United States works diligently to prevent a measles outbreak from occurring by immunizing school-age children. It is advised that anyone who received a measles vaccine prior to 1980 be revaccinated to increase protection. When receiving the vaccine, also check to see how long it will be before the vaccine is effective. It may take a couple of days, if not weeks, to fully enter the person's system and begin protecting against the virus.