Name: Sumara Choudhry
Lab Section: CRB

Disease

Measles

Causative Agents

Measles is caused by the Paramyxovirus, belonging to the family Paramyxoviridae. Paramyxoviruses are single stranded RNA viruses. Ranging from 60-100 nanometers (def), these types of viruses all have helical symmetry and have somewhat of an irregular shape due to the fact that the helical capsid (def) is wound in a lose sphere. They are negative-sensed enveloped virions (def) with spherical, filamentous or pleomorphic (def) forms. Their surfaces are studded with fusion and attachment proteins that appear as spikes, and inside the envelope, matrix proteins stabilize the structure. The nucleocapsid (def) cores contain nucleocapsid proteins, polymerase (def) proteins, RNA, and phosphoprotiens.

Epidemiology

Measles is typically spread through the respiratory tract, and is typically highly contagious due to its nature of being able to remain infectious in droplets in the air or respiratory secretions even after several hours without the host.

Measles is the most highly contagious viral infection that kills more children than any other disease that has an effective vaccine. Newborns have a natural immunity to the disease until they reach the age of about eight months old, for they still have the mother's immunity which they acquired in the womb to protect them. Throughout the world, more than 40 million people are infected, with the death tolls totaling over 750,000 each year. Although there is no one specific area where measles outbreaks are concentrated, the most are commonly found in the Eastern and South Eastern regions of the world, especially Africa, where in 2001, almost half a million cases were reported. In the United States and developed European countries, the threat of measles has been eliminated in the past two decades. Prior to an effective vaccine, large-scale outbreaks occurred in the winter/spring every 2-3 years, even in developed countries. Lack of proper infrastructure and inadequate healthcare systems, poor sanitation, and lack of enough food all contribute to the transmission of measles.

Transmission

Measles is spread through the respiratory route by either coughing or sneezing, and direct or personal contact with infected mucous membranes or bodily secretions that could contain the virus. Highly resistant and contagious, it can remain on surfaces or in the air for up to two hours. Following transmission from an infected host to a healthy host, the healthy host does not become sick immediately. Upon transmission, the virus migrates to the back of the throat and into the lungs. Once here, the virus replicates and begins to multiply. The approximate incubation(def) period is between 8-12 days from the time infected to the time the symptoms begin to show.

Signs and Symptoms

Several days after the date of transmission do the first signs of the characteristic measles symptoms appear. Fever, runny nose, red eyes, and coughing are all among the first symptoms of the disease. This is followed by a rash a few days later that lines the mucosal membrane of the mouth. This rash has a unique characteristic to it, small white granular-shaped dots, called the Koplik spots, on a reddish bump, characteristic of measles only.

As the days progress, the rash has a characteristic progression, starting from the head and slowly traveling to the neck, trunk, the abdomen and then the extremities (def) of the body. Starting out as a typical rash with reddish patches, bumps start to appear and soon become extremely itchy and irritating. As the rash spreads, the fever usually climbs higher, reaching as high as 106 degrees Fahrenheit. Diarrhea, nausea, and vomiting, as well as swollen lymph nodes (def) are added on to the cocktail of symptoms, with the cough becoming more severe and more painful in the throat.

Around 10-15% of all patients, especially children, develop bacterial complications along with the virus, such as pneumonia (def) and sinus infections. Further complications can cause more viral infections on the already immuno-compromised host, including bronchitis (def), laryngitis (def), croup (def), etc. Severe complications, such as encephalitis (def) can occur even after the initial symptoms have been resolved. This can further develop into a rare but fatal complication called subacute sclerosing panencephalitis (def), which can ultimately cause destruction of the entire brain, and inevitably, death.

Prevention and Treatment

Other than emotional and supportive treatment, as well as making sure the patient is taking antibiotics against potential bacterial infections, there is really no cure or antiviral therapy for the measles. Due to the extensive medical technology, measles has become a highly preventable infection. Containing tiny doses of living, inactivate viruses, the vaccine allows the immune system to develop antibodies(def) to the infection following vaccination. At approximately 15 months, a child should receive his first dose of measles vaccine. In order to ensure a strong enough reaction to prevent any future infections, a second dose is usually given when the child reaches the age of approximately 10 -12 years.

Bibliography

CDC. National Center for Immunization and Respiratory Diseases (NCIRD), Division of Viral Diseases. Measles. Retrieved April 13, 2010 from http://www.cdc.gov/measles/about/overview.html