Measles has been getting a lot of press lately. What exactly is this disease?

Measles is caused by a virus whose genetic material is in the form of single-stranded RNA. The virus can be contracted from the air--it can hang out there, still infectious, for about two hours after an infected person coughs or sneezes it out--or through directly touching saliva or mucus from an infected person. It’s actually considered one of the most easily transmitted diseases known to man. About 9 out of 10 people who come in contact with it will get infected!

The most characteristic symptom of measles is not the blotchy body rash but some whitish-gray spots that appear on the inside lining of the cheeks. These are called Koplik spots, named after the doctor that described them in 1896. They tend to show up a few days before the rash does in at least 50-70% of patients.

Patients with measles also tend to get flu-like symptoms (fever, cough, runny nose) and conjunctivitis (pink eye.) Because the virus suppresses the immune system, children with the disease will often contract other diseases--pneumonia, ear infections, gastroenteritis (vomiting and diarrhea) and croup (an upper airway infection.) About 1 out of every 1,000 people with measles develop brain inflammation, which can cause permanent damage. 1 to 3 out of 1,000 will die.

There is no specific treatment for measles. Vitamin A supplements have been found to be helpful, and antibiotics can be given for those additional diseases a measles patient might get. Most therapy is simply supportive--making sure a patient with diarrhea stays hydrated, for example.

Before the measles vaccine was released, it’s estimated that 3 to 4 million people were infected every year in the United States. This is an estimate because most cases were not reported--the disease was so common that over 90% of people were infected by age 20. We do know that in the 1950s about 48,000 people in the US were hospitalized due to measles and about 1,000 developed chronic disabilities from it.

An attenuated (weakened) measles vaccine produced by John Enders and his co-workers was licensed in 1963. This vaccine worked but had too many side effects, so Maurice Hilleman took that weakened strain of virus and made it even weaker by passing it through chick embryos another 40 times. This version was what ended up being combined with mumps and rubella vaccines in the MMR shot, which is the one still in use today.

Unfortunately, though the CDC declared measles eliminated from the US in 2000, new cases have been cropping up due to people not getting vaccinated and traveling outside of the country. Measles is still around in developing countries and kills over 100,000 people worldwide every year. The two-dose series of the vaccine is 97% effective at preventing the disease and, as recent research has shown, because the virus’ immune-suppressing effect lasts a good 2-3 years, saving people from infection through vaccination has brought down childhood deaths in general from 30% up to 90% in poor countries.

Here's a disease that you don't hear about very often--leprosy. Now referred to as Hansen's disease after the Norwegian physician that isolated its causative agent in 1873, it's an infection of the organism Mycobacterium leprae. Contrary to popular belief, this bacterium is actually not very contagious and multiples very slowly in the body, dividing once about every 13 days. An estimated 95% of the population is not susceptible to infection.

M. leprae is believed to be spread through coughing and sneezing. Unless nerve involvement occurs, the disease basically manifests as a skin condition, like in the picture above. The loss of fingers, toes, etc. happens as a result of secondary infections, particularly when patients lose sensation in these areas and can't tell when the skin is broken (this is also a huge problem for people with diabetes, who can lose feeling in their feet and develop ulcers there.)

The first effective treatment for Hansen's disease dates to 1941. Promin, a sulfa drug, was used to cure patients at an institution for lepers in Carville, Louisiana. Because it had to be given by injection, it was replaced by an oral medication, dapsone, in the 1950s. A multidrug regimen consisting of dapsone, clofazimine and rifampicin is used today, since some strains of the bacterium have developed resistance to dapsone alone.

About 150-200 new cases of Hansen's disease occur every year in the US. It is still a significant disease in poor countries and a focus of public health efforts. Though some headway has been made, as of 2012, about 30,000 new cases still crop up yearly in Africa, and about 90% of beggars there are believed to be cured Hansen's disease patients with permanent disfigurement.

Exciting news from the Carter Center, which announced yesterday that only 126 guinea worm cases were reported last year (versus 3.5 million cases in the mid-1980s!)

Guinea worm disease is caused by an organism called Dracunculus medinensis. This worm's larvae infect water fleas, which pass into people when they drink contaminated water. Though the stomach acids kill the water fleas, the worms survive and grow in the body and come out in horrific fashion through the skin. There is no vaccine for the disease or medication to treat it, but it can be prevented through filtering drinking water, like with the nifty personal pipe filters shown here.

If you live in the US, you might have heard that the flu vaccine released this year is not a "good match" for the viruses going around. How could this have happened?

Influenza viruses have proteins on their surfaces that the immune system can recognize. Two of these proteins are called hemagglutinin (HA, shown in the graphic above) and neuraminidase (NA), which are the "H" and "N" found in the virus names. One of the reasons why flu viruses are so successful is because they can easily mutate and change the structure of these proteins. Here are two ways in which these mutations can happen:

Many of the H3N2 viruses circulating this season have undergone drift. Their antigens have become different from the H3N2 strain (dubbed A/Texas/50/2012) that researchers predicted would be most common. Because it takes about six months to develop and release a flu vaccine, researchers have to start early, drawing up a projection from data reported to the World Health Organization from 111 different countries. Sometimes the viruses will undergo changes during those six months, causing the vaccine to be less effective.

So should you still get the flu vaccine? Yes! Even though the H3N2 viruses' surface proteins have changed, there is still a good chance that the H3N2 virus parts in the vaccine are similar enough to them that the vaccine can help teach the immune system to respond to them. There are also other two other viruses included in the vaccine that it can help protect you from.

The CDC has a nifty little vaccination pledge you can fill out if you have gotten the vaccine or are ready to get it.

You can read more about the flu vaccine, its safety and why it's so important here.

Psychiatry is still a relatively young branch of medicine--even today, the physiology behind many mental illnesses remains poorly understood. Because of this, it wasn't too long ago that the field was full of bizarre methods of treatment. Here are a few of the defunct ones:

Gregg Gonsalves, co-director of the Yale Global Health Justice Partnership and AIDS activist, making a powerful point about the American response to Ebola.

Where did Ebola come from? Here's a brief history of the disease:

Ebola was first discovered in 1976. Two outbreaks occurred that year--one in Sudan, and one in what was then called Zaire (now the Democratic Republic of the Congo.) The Sudan subtype of the virus infected 284 individuals and killed 150 of them, while the Zaire strain racked up a grisly total of 284 out of 318 cases. As often is the case, health officials needed a name for the disease, but didn't want to associate a town or region with it, so they named it after a river located near the second outbreak--the river Ebola.

A single case popped up in 1977, with a 9-year-old girl dying from the Zaire strain. She did not personally transmit it to anyone, but in 1979, the Sudan strain struck again, claiming the lives of 22 out of 34 cases. After that, the virus vanished for about fifteen years, with its origins still a mystery.

It would not show up again until the 1990s, beginning with a single isolated case near Liberia of a unique strain that was dubbed Ebola Ivory Coast. This case, an anthropologist who had come in contact with an infected chimpanzee, survived.

Zaire came roaring back in 1995, killing 256 out of 315 infected individuals--a staggering mortality rate of 81%. This outbreak occurred in a large city, with the virus passing easily between patients in two of the local hospitals. Several other Zaire strain outbreaks followed, some of which were linked back to individuals that had handled dead animals, such as chimpanzees, antelopes and gorillas. As of 2005, thirteen outbreaks had occurred, all confined to Africa.

In the 70s and 90s, scientists searched feverishly for a reservoir--an animal that could carry the virus without quickly dying of it, much like pigs and birds with influenza. Apes didn't seem to fit, because Ebola made fast work of them. Maybe it was rats or mice. One strain, Reston Ebola, was found in both macaques and pigs, and became a cause for concern because some work suggested that it might be able to transmit through the air. However, this distinctive strain wasn't able to cause infection in humans; while antibody tests showed that several people had been exposed, none developed symptoms.

What about bats? In the early 2000s researchers found three species of fruit bats that carried Zaire Ebola RNA and Ebola antibodies (one of these, H. monstrosus, is pictured above.) They were unable to isolate the virus itself from any of the bats, but this possibility continues to look promising, especially because another related virus, Marburg virus, has been isolated from bats and outbreaks of Marburg have been connected back to bat habitats.

It still isn't known exactly what brought Ebola out to humans. Research is ongoing, as are attempts to get the virus under control as quickly as possible.

You can read more about Ebola in my previous post, or hear what some experts from my school have to say about the disease here.

Here's some neat medical news--there are cells in the olfactory bulb, the part of the brain governing the sense of smell, that can actually replenish nerves throughout life. These nifty cells, called olfactory ensheathing cells (OECs), are related to the Schwann cells that cover neurons and help speed up their signal transmission. Researchers have been interested in using OECs to help patients with nerve damage for about a decade, and they've finally managed it with this man, who was paralyzed from the chest down after being attacked with a knife.

I love the comment of one of the scientists involved too:

Have questions about Ebola? Experts at University of Michigan School of Public Health put together a series of videos about how the virus works, why the current outbreak is so bad and how much we should be concerned. You can find the rest of them here.