How to MeaslesTransmission

MeaslesTransmission -

Measles is highly contagious and can be spread to others from four days before to four days after the rash appears. Measles is so contagious that if one person has it, 90% of the people close to that person who are not immune will also become infected with the measles virus.

The virus lives in the mucus in the nose and throat of the infected person. When that person sneezes or coughs, droplets spray into the air. The droplets can get into other people’s noses or throats when they breathe or put their fingers in their mouth or nose after touching an infected surface. The virus can live on infected surfaces for up to 2 hours and spreads so easily that people who are not immune will probably get it when they come close to someone who is infected.

Who is at risk?

Unvaccinated young children are at highest risk of measles and its complications, 

including death. Unvaccinated pregnant women are also at risk. Any non-immune person 

can become infected.

Measles is still common in many developing countries – particularly in parts of Africa and 

Asia. More than 20 million people are affected by measles each year. The overwhelming 

majority (more than 95%) of measles deaths occur in countries with low per capita i

ncomes and weak health infrastructures.

Measles outbreaks can be particularly deadly in countries experiencing or recovering 

from a natural disaster or conflict. Damage to health infrastructure and health services 

interrupts routine immunization, and overcrowding in residential camps greatly increases 

the risk of infection.

Structure of Measles Virus...

Structure of Measles-

Structure of Measles Virus

• Structure of Measles Virus-
• 
  
• Measles virus is a member of the genus Morbillivirus of the family Paramyxoviridae
• Measles) virus is a typical paramyxovirus (spherical enveloped particles that contain a non segmented negative strand RNA genome)
• Measles virus have two types of envelope spikes that shows:

    Hemagglutinating activity

Cell fusion and hemolytic activity

• Single serotype i.e. Life long immunity occurs in individuals who have had the disease.
• Hemagglutinin is the antigen against which neutralizing antibody is formed.
• Infants are protected during the first six months of life ( they get maternal antibody as it passes the placenta)

Replication cycle of Measles Virus

• Adsoprtion to the cell surface: via Hemagglutinin. Cellular receptor of measles virus is CD46 molecule.
• Penetrates the cell surface and uncoats
• Virion RNA polymerase transcribes the negative-strand genome to mRNA
• Specific viral proteins are formed
• Assembly to helical nucleocapsid
• Release of virus by budding

Transmission and Epidemiology of Measles

• Worldwide distribution, outbreaks in 2-3 years
• Transmitted via respiratory droplets produced by sneeze or cough during prodromal period which continues up to few days after rash appears
• Measles virus is extremely infectious, most children contract clinical disease on exposure
• More serious outcomes in Malnurished children, people with deficient cell mediated immunity.

Pathogenesis

• Measles virus infects the cells lining the upper respiratory tracts
• Enters blood and infects reticuloendothelial cells and replicates again.
• Spread to skins
• Appearances of rash: (because of cytotoxic T cells attacks measles virus infected vascular endothelial cells in the skin).
• Formation of Multinucleated giant cells.

Clinical features of Measles

• Incubation period: 10-14 days
• Prodromal phase: Characterized by fever, conjunctivitis (causing photophobia), running nose, and coughing
• Appearance of Koplik’s spot (bright red lesions with the white, central dot) # Diagnostic feature
• Appearance  of Maculopapular rashes, common features of which includes:
  
  

  Child infected with Measles
  Source:: CDC
• Occurs 5‐7 days after symptoms    
• Lasts 3 or more days
• Brownish hue
• Progresses from face to body to extremities
• Rash becomes confluent as it progresses
• Rash affects palms and soles
• Soon after the rash appears, the patient is no longer infectious.

Complications  because of Measles infections

• Encephalitis: 1 per 1000 cases
• Subacute sclerosing panencephalitis (SSPE): Fatal disease of nervous system can develop after several years after measles.
• Giant cell pneumonia
• Co-infections:

–     Secondary bacterial pneumonia –     Bacterial otitis media

• Increased risk of still birth in pregnant women infected with measles.
• Measles virus infection of fetus causes fetal death
• Atypical measles develops in some people who were given killed vaccine and subsequently infected with measles virus.

Key Facts about Measles

Key facts-

• Measles is one of the leading causes of death among young children even though a safe and cost-effective vaccine is available.
• 
  
• In 2012, there were 122 000 measles deaths globally – about 330 deaths every day or 14 deaths every hour.
• Measles vaccination resulted in a 78% drop in measles deaths between 2000 and 2012 worldwide.
• 
  
• In 2012, about 84% of the world's children received one dose of measles vaccine by their first birthday through routine health services – up from 72% in 2000.
• Since 2000, more than 1 billion children in high risk countries were vaccinated against the disease through mass vaccination campaigns ― about 145 million of them in 2012.

signs and symptoms measles

 The classic signs and symptoms of measles include four-day fevers [ the 4 D's ] and the three Cs—cough, coryza (head cold), andconjunctivitis (red eyes)—along with fever and rashes. The fever may reach up to 40 °C (104 °F). Koplik's spots seen inside the mouth arepathognomonic (diagnostic) for measles, but are not often seen, even in confirmed cases of measles, because they are transient and may disappear within a day of arising. Their recognition, before the affected person reaches maximum infectivity can be used to reduce spread of epidemics.
The characteristic measles rash is classically described as a generalized, maculopapular, erythematous rash that begins several days after the fever starts. It starts on the back of the ears and, after a few hours, spreads to the head and neck before spreading to cover most of the body, often causing itching. The measles rash appears two to four days after the initial symptoms and lasts for up to eight days. The rash is said to "stain", changing color from red to dark brown, before disappearing.

History-


The Antonine Plague, 165–180 AD, also known as the Plague of Galen, who described it, was probably smallpox or measles. The epidemic may have claimed the life of Roman emperor Lucius Verus. Total deaths have been estimated at five million.[83] Estimates of the timing of evolution of measles seem to suggest this plague was something other than measles. The first scientific description of measles and its distinction from smallpox and chickenpox is credited to the Persian physician Rhazes (860–932), who published The Book of Smallpox and Measles.[84] Given what is now known about the evolution of measles, this account is remarkably timely.


16th century Aztec drawing of someone with measles
Measles is an endemic disease, meaning it has been continually present in a community, and many people develop resistance. In populations not exposed to measles, exposure to the new disease can be devastating. In 1529, a measles outbreak in Cuba killed two-thirds of the natives who had previously survived smallpox. Two years later, measles was responsible for the deaths of half the population of Honduras, and had ravaged Mexico, Central America, and the Inca civilization.


Between roughly 1855 to 2005 measles has been estimated to have killed about 200 million people worldwide Measles killed 20 percent of Hawaii's population in the 1850s. In 1875, measles killed over 40,000 Fijians, approximately one-third of the population.[88] In the 19th century, the disease decimated the Andamanese population.] In 1954, the virus causing the disease was isolated from an 11-year old boy from the United States, David Edmonston, and adapted and propagated on chick embryo tissue culture. To date, 21 strains of the measles virus have been identified.[91] While at Merck, Maurice Hilleman developed the first successful vaccine. Licensed vaccines to prevent the disease became available in 1963.[93] An improved measles vaccine became available in 1968.