Measles

The measles is a highly contagious airborne pathogen which spreads primarily via the respiratory system. The virus is transmitted in respiratory secretions, and can be passed from person to person via aerosol droplets containing virus particles, such as those produced by a coughing patient. Once transmission occurs, the virus infects and replicates in the lymphatic system, urinary tract, conjunctivae, blood vessels and central nervous system of its new host.^[1] The role of epithelial cells is uncertain, but the virus must infect them to spread to a new individual.^[2]
Patients with the measles should be placed on droplet precautions.
Humans are the only known natural hosts of measles, although the virus can infect some non-human primate species.


Complications

Complications with measles are relatively common, ranging from relatively mild and less serious diarrhea, to pneumonia and encephalitis (subacute sclerosing panencephalitis), corneal ulceration leading to corneal scarring.^[3] Complications are usually more severe amongst adults who catch the virus.
The fatality rate from measles for otherwise healthy people in developed countries is 3 deaths per thousand cases.^[4] In underdeveloped nations with high rates of malnutrition and poor healthcare, fatality rates have been as high as 28%.^[4] In immunocompromised patients, the fatality rate is approximately 30 percent.^[5]


Prevention and Public health


In developed countries, most children are immunized against measles by the age of 18 months, generally as part of a three-part MMR vaccine (measles, mumps, and rubella). The vaccination is generally not given earlier than this because children younger than 18 months usually retain anti-measles immunoglobulins (antibodies) transmitted from the mother during pregnancy. A second dose is usually given to children between the ages of four and five, in order to increase rates of immunity. Vaccination rates have been high enough to make measles relatively uncommon. Even a single case in a college dormitory or similar setting is often met with a local vaccination program, in case any of the people exposed are not already immune.
In developing countries where measles is highly endemic, the WHO recommend that two doses of vaccine be given at six months and at nine months of age. The vaccine should be given whether the child is HIV-infected or not.^[6] The vaccine is less effective in HIV-infected infants, but the risk of adverse reactions is low.
Unvaccinated populations are at risk for the disease. After vaccination rates dropped in northern Nigeria in the early 2000s due to religious and political objections, the number of cases rose significantly, and hundreds of children died.^[7] A 2005 measles outbreak in Indiana was attributed to children whose parents refused vaccination.^[8] In the early 2000s the MMR vaccine controversy in the United Kingdom regarding a potential link between the combined MMR vaccine (vaccinating children from mumps, measles and rubella) and autism prompted a comeback in the measles party, where parents deliberately infect the child with measles to build up the child's immunity without an injection. This practice poses many health risks to the child, and has been discouraged by the public health authorities.^[9] Scientific evidence provides no support for the hypothesis that MMR plays a role in causing autism.^[10] However, the MMR scare in Britain caused uptake of the vaccine to plunge, and measles cases came back: 2007 saw 971 cases in England and Wales, the biggest rise in occurrence in measles cases since records began in 1995.^[11]
According to the World Health Organization (WHO), measles is a leading cause of vaccine-preventable childhood mortality. Worldwide, the fatality rate has been significantly reduced by partners in the Measles Initiative: the American Red Cross, the United States Centers for Disease Control and Prevention (CDC), the United Nations Foundation, UNICEF and the World Health Organization (WHO). Globally, measles deaths are down 60 percent, from an estimated 873,000 deaths in 1999 to 345,000 in 2005. Africa has seen the most success, with annual measles deaths falling by 75 percent in just 5 years, from an estimated 506,000 to 126,000.^[12]
The joint press release by members of the Measles Initiative brings to light another benefit of the fight against measles: "Measles vaccination campaigns are contributing to the reduction of child deaths from other causes. They have become a channel for the delivery of other life-saving interventions, such as bed nets to protect against malaria, de-worming medicine and vitamin A supplements. Combining measles immunization with other health interventions is a contribution to the achievement of Millennium Development Goal Number 4: a two-thirds reduction in child deaths between 1990 and 2015^]