Now, we'll cover measles. Rubeola. Measles is a childhood infection caused by a virus.
It is vaccine-preventable, also called rubeola, and it can be serious and have fatal complications.
This is caused by the measles virus which is a single-stranded RNA virus.
This is going to affect about 20 million people worldwide and this can affect people of any age.
This is one of the leading vaccine-preventable diseases than can cause death.
The risk of death is about 0.2% but it can be up to 10% in patients with associated malnutrition.
Most patients who die are less than 5 years old.
So we know that measles emerged around 500 AD
and it was differentiated from smallpox and chickenpox a couple hundred years later.
The vaccine was developed by Maurice Hilleman and this prevents 1 million deaths per year.
Here we see some notable outbreaks of measles.
In 1529 in Cuba, this killed about two-thirds of the population.
A couple years later in Honduras, this killed 50% of the population.
And then in the 1850s in Hawaii, an outbreak killed 20% of the population.
In 1875 in Fiji, a third of the population was killed by measles.
And between 1855 and 2005, this has killed about 200 million people worldwide.
About 7-8 million children died each year before this vaccine was introduced.
So, measles. It has a reputation. It is highly contagious.
About 90% of susceptible people who are exposed to someone with the measles virus will be infected.
Now, this is gonna replicate in the nose and the throat of an infected child or adult
and it's gonna be transmitted by droplets which are coughing, sneezing, laughing, or talking.
So the tricky thing about measles is it can live in the air for up to 2 hours after an infected person has passed.
If they're talking, coughing, sneezing, and you can imagine how this can spread
like wildfire in the setting of an airport, a public bus, a school, or a hospital.
So where I work, if we have a patient checking in for possible measles,
the team will log all of the patients and family members who've been in the same airspace
within 2 hours of the patients and those new patients will be contacted about a possible measles exposure.
And also in the newspaper, announcements will be made to the community
about possible areas of exposure including grocery stores, restaurants, and other public places
through which the patient may have passed.
For this reason, measles is a public health nightmare to contain.
Here we see the maximum number of people on average that can be infected by one sick person.
So if you look down through the list, do you see? Measles is at the bottom.
About 18 people can be infected by one patient with measles.
So what happens after the measles virus is inhaled?
Well, it's going to enter the mucosa and infect the epithelial cells in the trachea and the bronchi.
It's gonna use the protein hemagglutinin or the H protein to bind to the target receptor on the host cell.
It's going to have the signal lymphocite activation molecule or SLAM found
on the immune cells, the B cells, the T cells, and the antigen-presenting cells.
And this is gonna fuse with the membrane and get inside the cell.
There, it's gonna be transcribed by RNA polymerase.
Then it will be translated into viral proteins.
They will be coated in a lipid envelope and sent out as a newly made virus.
This is ready to spread to the local tissues carried by macrophages
from the local tissue in the lungs and the lymph nodes.
There, it will get into the blood and spread to the other organs like the intestines and the brain.
Then, it will spread to be a skin rash.
It's gonna be released from the epithelial cells in the respiratory tract.