Procopius, writing in Constantinople (now Istanbul) in 542 C.E., complained that the plague had killed nearly everyone in the city. Eight hundred years later in Italy, Boccaccio described the disastrous Black Death, which killed a third to a half of the population of Europe. In 1855, twelve million people in India and China alone died from the same cause. And these terrible statistics only tell us about one disease. There are others. There were more victims of the 1918 Spanish flu epidemic – which did not actually come from Spain – than the total number of casualties in the First World War. In 2010, malaria killed 1.25 million people, 65% of them under fifteen years of age. There are also new diseases that cannot be cured, like SARS, ebola and AIDS. AIDS has killed more than thirty million people in about thirty-five years. And now we have Covid 19!
Why are there Diseases and Can we Ever Make a World Without
Them?
Procopius, writing in Constantinople
(now Istanbul) in 542 C.E., complained that the plague had killed
nearly everyone in the city. Eight hundred years later in Italy, Boccaccio
described the disastrous Black Death, which killed a third to a half
of the population of Europe. In 1855, twelve million people in India and China
alone died from the same cause. And these terrible statistics
only tell us about one disease. There are others. There were more victims of
the 1918 Spanish flu epidemic – which did not actually come from
Spain – than the total number of casualties in the First World War. In 2010,
malaria killed 1.25 million people, 65% of them under fifteen years of age.
There are also new diseases that cannot be cured, like SARS, ebola and
AIDS. AIDS has killed more than thirty million people in about thirty-five
years. And now we have Covid 19!
But where does disease come from and
can modern medicine ever create a world without it?
So, when and where did disease start?
For a disease to spread quickly, there must be a large population living close
together in a city. Scientists think the number is about half a million. This
usually means there are animals living very near them, so that they can easily
get milk, eggs and meat to eat and skins to wear.
Most epidemic diseases come from animals (although some –
like leprosy – travel in the opposite direction from human beings to
animals). So, an epidemic starts when people get in the way of a normal
animal to animal infection. For instance, plague happens
when fleas (that
live on rats and cause them to become ill) find healthy human blood and pass
the disease from the rat to the person. People also eat diseased meat. For
example, the ebola outbreak in Zambia in 2012 probably came from
people hunting and eating sick animals. The disease can sometimes then pass
from a person to family members, friends and so on through
touching, sneezing or sex.
In ancient communities, there
was not so much travel between different groups and so a disease could kill all
the people in a town and then die out. However, if people moved from one town
to the next, probably to trade, they carried the disease or the fleas with
them and the disease spread there too. As soon as they travelled by ship, they
took fleas
overseas
to bite the local population of a new land. Of course, people carrying a
disease but not yet sick fly to other parts of the world nowadays and
so epidemics can spread much faster.
But we know so much about medicine
these days. Isn’t there some way to stop disease spreading?
In fact, one of the best is prevention through
education. Although 30 million people have now died of AIDS, for example, we
can be sure that number would be much, much higher if everyone still had unprotected sex.
The gay population in Europe quickly learnt to
use condoms to avoid the same increase in the disease as
happened in the States, for instance. Malaria still kills more than a million
people a year, but the numbers were once much higher. Although there is still
no vaccination available,
its numbers have fallen because people use mosquito
nets from dusk to dawn and so do not get bitten so
often.
Education has also been very important
in changing the ways people think about disease. Until the nineteenth century,
people usually asked why they were
sick and not their neighbours or friends (or, more happily, enemies). This did
not help much. But, as science advanced, attitudes changed and people
began to ask what disease they had and what they could do to control it.
(Nowadays, of course, as genetic explanations play a larger role in our
understanding of disease, we have started to ask once again why we have got
lung cancer when we do not use cigarettes while our chain-smoking neighbour
has not.)
Another point is that we now have very
advanced medicine. Surely, this must help to control the spread of disease or
even cure it?
The fact is that bacteria, one of the
two causes of disease – the other is viruses – have been on this planet for
millions of generations, while human beings only go back about 20,000. This
means that bacteria have moved back and forth between animals and people for
thousands of years and their genetic codes have changed and continue to
change as a result. From the discovery of a disease to the invention of a vaccine
or treatment typically takes ten to fifteen years, if there are not too many
different government controls and tests. Many people can die in that time, of
course, as we have seen with AIDS. However, by the time we have developed
an effective medicine, the virus or bacteria might not have the same
chemistry or DNA as it had when we first noticed the disease and so the
medicine needs to adapt too. In other words, we are always two or
three steps behind the disease.
It is also for this reason we can be sure more diseases will appear in the twenty-first century as new genetic combinations occur and human beings get in the way and become infected. As we walk more and more crowded streets, attend bigger and bigger universities and travel further and further, these new diseases will spread … inevitably and unstoppably.
If you want to watch some videos on this topic, you can click on the links to YouTube videos below.
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Videos :
6. Bacteria and Viruses (3:19)