For the past 30 years, the number of outbreaks of the virus has increased and rapidly spreading diseases, such as coronavirus in China today, are becoming more common. The world’s population is currently 7.7 billion, and we live closer to each other.
More people in reduced spaces implies a higher risk of exposure to pathogens that cause disease. Wuhan coronavirus appears to be spread from person to person by droplets when it coughs or sneezes. The virus survives for a limited time outside the body, so people have to be relatively close to each other to spread it.
In 2014, the Ebola epidemic spread through blood or other body fluids; only people in close contact could catch it. But not all viruses are transmitted from person to person. Even Zika, who passes from mosquitoes to humans, is made more accessible when we are nearby. Zika mosquitoes thrive in urban areas where they can feed on human blood. They reproduce well in densely populated, humid, and warm places.
Since 2007, more humans have lived in cities. More than four billion people live today on 1% of the earth’s land surface. And many of the towns where we settle are not ready for us. So many people end up in slums where they don’t have clean running water or a proper sewage system, so diseases spread quickly. Planes, trains, and cars mean that a virus can travel half the globe in less than a day. A few weeks after the appearance of the coronavirus, cases were suspected in more than 16 countries. In 2019, airlines carried 4.5 billion passengers, up from 2.4 billion just ten years earlier.
Wuhan is one of the main stations of Chinese high-speed rail service, and the virus struck at the time when China was about to embark on the greatest human migration in history – more than three billion journeys are made across the country on the occasion of Chinese New Year. One of the worst pandemics ever recorded was the 1918 flu, known as the Spanish flu. It erupted in Europe during another era of mass migration, towards the end of the First World War.
As the flu spread, the soldiers returned to their country and brought the flu with them. They brought the virus to communities that had not developed resistance to the infection, taking the immune system entirely by surprise. According to a study by virologist John Oxford, the source of the virus could have been a transit camp, through which approximately 100,000 soldiers passed daily.
Even before air travel, the epidemic spread to almost all regions of the world. It has killed between 50 and 100 million people. It still took six to nine months for the Spanish flu to spread around the world. In a world where we can circumnavigate the globe in one day, a new flu virus could spread much faster.
Ebola, SARS, and now Wuhan coronavirus are all zoonotic viruses – they have been transmitted to humans by animals. The new coronavirus appears to have come from a meat market in Wuhan – early studies indicate it could have come from live snakes.
Today, about three out of four new diseases are zoonoses.
Our world desire for meat increases, animal agriculture, develops as certain parts of the world get more luxurious and get a taste for a more balanced diet. Influenza viruses tend to reach humans through pets. The likelihood of infected animals coming into contact with humans is, therefore, also increasing. Coronaviruses pass from wild animals to humans. In China, live animal and meat markets are conventional in densely populated areas. This could explain why two of the last epidemics started in this country.
On the other hand, as our cities grow, we are sinking into rural areas where humans come into contact with wild animals. Lassa fever is one of the viruses that spread in this way: while people cut forests to use the land for agricultural purposes, rats living on the earth take refuge in houses and bring fever with them from Lassa.
When the Ebola virus struck West Africa in 2013, it had never been seen before, and medical personnel was slow to detect it. Although the world is more connected than ever, we still do not have a global health system capable of responding to these threats. To stem the epidemic, we count on the government of the country where it is declared. If they fail, the whole planet is in danger.
Nowhere was this more evident than in West Africa during the Ebola epidemic. When local health systems in Guinea, Liberia, and Sierra Leone failed, and the virus spread. The Ebola virus has killed 11,310 people in West Africa. Fortunately for the rest of the world, it is a virus that spreads relatively slowly, but respiratory infections like the flu or the coronavirus spread much faster.