Cholera. You’ve probably heard about this disease that’s plagued the world for centuries,
spreading around sickening and killing millions. But what you probably didn’t know is that
the disease has created one of the world’s longest pandemics ... ever. So what exactly
does cholera do to the body? How can we prevent it? And why has this ancient disease lasted
throughout the ages?
It's actually a good time to be talking about cholera because of the COVID pandemic right
now because cholera causes pandemics and we've had seven pandemics of cholera in the last
200 years.
I am Anita Zaidi and I'm the director for the Bill and Melinda Gates Foundation
in enteric and diarrheal diseases.
First discovered in the Ganges delta in India, Cholera is caused by the bacteria vibrio cholerae.
And it’s been around since ancient times, with multiple pandemics starting in 1817.
During that first outbreak was when the world really got to know about this disease. Out
of the more than 200 serogroups of V. cholerae, only two are known to actually cause Cholera:
O1 which is responsible for most of the recent outbreaks, and O139 which is linked to more isolated
cases. So how exactly does the bacteria spread?
Well, that mystery was solved thanks to a pump back in 1854.
John Snow is like one of those legendary epidemiology figures that everybody learns about when they
learn about cholera. John Snow noticed, that there was a lot of cholera happening in London
and he started looking at the patterns of how cholera was spreading and he noticed that
the areas which had high incidence of cholera, all had a similar drinking source, a water pump.
And so he removed that water pump and it showed that cholera rates in those areas went down
and it's a famous epidemiology story about one smart person paying attention to patterns
of disease and figuring out how to stop it. And two centuries later, we’re still trying
to figure it out.
What we know is that when a person contracts cholera, it’s usually through a contaminated
source like drinking water that’s come into contact with infected feces. Now, after that
first sip, it takes the bacteria anywhere from a few hours to a couple of days to begin
wreaking havoc on the body.
When you ingest the bacteria, it goes from your mouth, into your esophagus, into your stomach, and then
pass the stomach and where it causes disease is in the small intestine.
Once there, the bacteria swims towards the intestinal wall, pushing through the thick
mucous layer of the intestines’ epithelial cells where it then attaches itself and begins
to multiply, releasing toxins that stimulate the cells to secrete water. And that’s where
the chaos begins.
What it does to the body is it will cause vomiting. It causes stomach pains. It causes
bad watery diarrhea. All of a sudden, all of the water in your body starts being secreted
through your intestinal cells. The secretion of fluids is so massive that you basically
pour out liters of fluid from your body. That's how cholera kills, right, because it just
dehydrates then all of the organs shut down. Like if you've seen a cholera dehydration in
your life once, you never forget it.
Oh and if that weren’t scary enough, that rapid loss of fluid can all happen within
a matter of hours of showing symptoms. Thankfully, only a minority of cases experience
this. While the rest have mild to moderate symptoms, developing bouts of nausea, vomiting,
and loose stools. But milder cases still present a threat because patients can excrete V. cholerae
for up to two weeks after the infection has passed.
Luckily though, we know how to treat it. For patients suffering, the most important thing
to do is to replace the rapid loss of minerals, so a solution of oral rehydration salts is
usually given and in the more extreme cases, IV fluids can be used to get the job done
faster. And to stem future spread, antibiotics can help reduce the amount of the bacteria
present in the stool.
As for prevention, there are two main methods: One is of course making sure that people have
access to clean water and sanitation and now we know much more about the types of areas
where cholera spreads, they're called hotspots, where there is a lot of people living in close
proximity, so high population density slums, inner city areas in developing countries and
typically they are close to a body of water.
While the other is vaccines. Currently, there’s the oral cholera vaccine, which is taken in
two doses one to two weeks apart. It’s the main one used in mass vaccination efforts
and it’s produced by two manufacturers: Euvichol and Shanchol. And the best part is,
is that it’s really cheap, at less than two dollars a dose.
This vaccine has now saved thousands and thousands of lives. 30 to 40 million doses are being
used every year in the cholera hotspots. This is for the first time that so many doses
of vaccines are being used that we are now seeing a number of deaths from cholera decreasing
in the world for the last two years and so that's really good news on cholera.
So if we know how to treat the disease and have a way to prevent it, then why is this
ancient disease still an issue today?
The reason that Cholera has persisted is that we have not addressed poverty to the level
that we should and with time we know how Cholera happens and where it happens and we should
be able to focus on those cholera hotspots as first priority for areas which need improved
sanitation and hygiene. And that's countries working together prioritizing health over
other things and improving their own infrastructure.
So when we can do that, cholera will disappear.
To help get there, the World Health Assembly,
which is the WHO’s decision making body, pledged to eradicate cholera by 2030, hoping
to reduce deaths worldwide by 90%. And if we can achieve that goal, we may soon see the
end of one of the world’s longest pandemics.
We have an opportunity to get rid of cholera from the world forever and also an opportunity
for the world to understand how we have worked together as a multinational effort, coming
together to control cholera as an infectious disease pandemic and what are the lessons
learned for controlling COVID in the same way.