The coronavirus disease, known as COVID , is a frightening reminder of the imminent global threat posed by emerging infectious diseases. Although epidemics have arisen during all of human history, they now seem to be on the rise. In just the past 20 years, coronaviruses alone have caused three major outbreaks worldwide. Even more troubling, the duration between these three pandemics has gotten shorter.
I am a virologist and associate director of the Animal Diagnostic Laboratory at Penn State University , and my laboratory studies zoonotic viruses, those that jump from animals and infect people. Most of the pandemics have at least one thing in common: They began their deadly work in Asia or Africa. The reasons why may surprise you. An unprecedented shift in human population is one reason why more diseases originate in Asia and Africa. According to the World Bank , almost million people moved to urban areas in East Asia during the first decade of the 21st century.
To put that into perspective, million people could form the eighth most populous country in the world. Migration on that scale means forest land is destroyed to create residential areas. Wild animals, forced to move closer to cities and towns, inevitably encounter domestic animals and the human population. Wild animals often harbor viruses; bats, for instance, can carry hundreds of them.
And viruses, jumping species to species , can ultimately infect people. The Asian H5N1 virus originating in poultry farms and sporadically infecting humans has so far killed over people, more than half those infected. Factory farming is especially prone to the emergence of dangerous pathogens, he says. Equally, avian and swine flu are still part of the genetic roulette [we are playing].
Intensive farming of wildlife, especially in Southeast Asia and China, concerns experts as well. Instead of farming a small range of animals like cattle, sheep, goats, poultry and pigs — to whose diseases humans have over centuries become partly immune — farmers are now breeding hundreds of different animals for both food and medicine with potential risk of pandemics.
One U. Food and Agriculture Organisation study in Vietnam found animal species being farmed , including ostriches, fruit bats, crocodiles, porcupines, flying foxes, turtles, crab-eating macaque monkeys, grasscutters, green pythons, civets, wildcats, deer, snakes and multiple rodents.
Veterinarians and epidemiologists argue that an important way to reduce the risk of future pandemics is to farm more sustainably. We are losing too many species, too many natural landscapes. We are intensifying agriculture in ways that are inhumane and unsustainable. Things that cannot go on forever will stop — often abruptly and nastily. D eadly diseases are also increasingly likely to spread from animals to humans in fast-growing cities where animals and humans are crowded together.
As people have migrated in from rural areas, the peri-urban areas that surround most cities in developing countries have become densely populated with people and animals. Urbanization is likely to lead to greater populations of urban wildlife like rats, foxes, skunks and possums, says Jamie Bartram, former head of the water, sanitation, hygiene and health at the WHO, now a professor of civil engineering at the University of Leeds and of public health at the University of North Carolina at Chapel Hill.
It is poor sanitation and water that spreads disease around densely packed cities, says Bartram. Waterborne zoonotic pathogens cause both gastrointestinal diseases like diarrhea and other illnesses like leptospirosis and hepatitis. One of the worst recent zoonotic incidents emerged in China, probably after a person became infected by a previously unknown coronavirus pathogen on a chicken farm in After the virus, which we now know as SARS, traveled to Hong Kong in an ill man, rats and cockroaches spread it through the drains and plumbing system of a dense cluster of 19 apartment blocks called Amoy Gardens.
More than people were infected, and 33 died before it was brought under control. SARS threatened to spread around the world but in the end traveled to only 29 countries, killing people.
Sign up now to receive our newsletter. SARS shows how fragile our cities are and how exposed people can be to virulent pandemic disease, he says. Underneath our cities are drainage and water systems which through rivers connect one city to the next and to food chains. A disease transmitted through water would be a big deal but would likely be localized. The way to reduce risk, he says, is to invest in accessible safe water and toilets for all.
It would pay itself back in health and productivity. The explosion in the number of pets and companion animals that now share their lives with humans also threatens to spread disease in new areas. In the U. The result is potentially serious epidemics. Bruno Chomel, a professor of veterinary medicine at the University of California, Davis, says affluence is leading to larger pet populations and possibly new diseases.
Our domesticated animals then can be a relay for some of these pathogens, such as flying foxes for Nipah virus and horses for Hendra. In some Middle East countries, it has become trendy to have exotic carnivores as pets. All people planning travel should become informed about the potential hazards of the countries they are traveling to. Learn how to reduce their risk of getting these diseases. It is believed that increased global travel is the reason for the recent renewal of many infectious diseases in the United States.
The number of people traveling internationally is increasing every year, and more people are taking trips to remote parts of the world. These often have unfamiliar health problems as well as underdeveloped healthcare services. Many travelers are also unaware of potential hazards in different parts of the world and do not take the necessary precautions.
These include getting necessary vaccines or taking preventive medicine. Many of the newly discovered infections have actually been in existence for a long time, but healthcare providers have not seen them in areas where new outbreaks happen.
With people's ability today to travel anywhere in the world within 36 hours or less, formerly little-known infections are picked up and rapidly spread to areas where they previously did not exist. Travel abroad does not need to result in an illness from infectious diseases.
Taking these measures can help reduce the risk to people traveling internationally:. Seek information as far before traveling as possible, even if the destination is one you have previously visited. Health conditions can change quickly in certain areas of the world. Get as much information as possible about current health risks for the country or countries you are visiting and learn about special risks for children, pregnant women, people with chronic diseases, and people with weakened immune systems who might be traveling with you.
For specific recommendations, see a travel medicine specialist or a healthcare provider familiar with the area you will be visiting at least 4 to 6 weeks before your trip. If you are pregnant or plan to become pregnant, make certain to ask a travel medicine specialist about any pregnancy-specific concerns in your travel area. Get the immunizations and take the preventive medicines recommended by your healthcare provider. Since some of these must be given or taken weeks before travel, contact your healthcare provider as early as possible to make sure that the effectiveness of these measures.
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