Animal Contact and Environmental Destruction: The Contagion Threat to Humanity

Out of the Wild

The world has been swept several times in recent years by viruses, humanity’s natural predator, resulting in many deaths. Examples include various Avian influenza strains, particularly the H5N1 subtype whose first human transmission was confirmed in 1997; SARS, or severe acute respiratory syndrome, first recognized in 2003; and Ebola virus disease, notably in 2014–16.

“The primary cause of the outbreak of infectious diseases has been the destruction of the natural environment by human beings,” explains Ishi Hiroyuki, a 79-year-old environmental journalist and author of Kansenshō no sekaishi (A World History of Infectious Diseases).

Human beings have long laid waste to forests and other parts of the natural environment in search of natural resources. Wild animals that had lived away from human beings have lost their habitats and sources of food, driving them into human-inhabited areas. The former clear line between humanity and the wild has been blurred, resulting in increased contact between wildlife and domesticated animals like livestock and pets—and the transmission of previously unknown viruses.

From 1976 to 2019, there were over 30 outbreaks of the Ebola virus in West Africa. This highly infectious disease causes deaths from the hemorrhaging of blood throughout a patient’s body. Ebola is one of the most powerful infectious diseases, and even dead patients remain contagious for a certain period of time. The animal that transmitted the disease is the “flying fox,” a fruit bat with a 1-meter wingspan living deep in the rainforest.

“Outbreaks of Ebola have occurred immediately after large areas of the forests in Africa were destroyed. One example is Gabon, where gold mines and other sites were developed in a rush to exploit the nation’s rich underground resources,” explains Ishi.

From Animals to People

As the consumption of meat expands worldwide, livestock are increasing in number. This has increased points of contact between human and animal populations, expanding infectious diseases and generating new types of illnesses. Beef, pork, poultry, and other meat sources are being mass produced to meet the demand for that increased meat consumption, but Ishi notes that this has had an “unexpected chain of consequences.”

From 1998 into the following year, over 100 people in Malaysian Borneo died of a disease whose symptoms included high fever and headaches. The military was sent to the area of the disease to cull the villagers’ pigs, which were thought to be transmitting the disease.

Pigs were being raised on Borneo, deep in the forests, to meet Singaporean demand for imported Malaysian pork. This was the result of a ban on domestic pig farms in the small island nation of Singapore in response to protests about the foul odors generated by such farms. The pigs raised in Borneo were infected by a virus spread by the urine of fruit bats inhabiting that area, and the disease—a new type of Nipah virus infection—was then transmitted to human beings. It later spread to India and other parts of Asia, resulting in around 10 separate outbreaks.

Animal populations do not have to be raised as food to pose a threat to people. Wetlands that serve as wintering areas for migrating birds have been gradually disappearing in recent years. This has influenced the ferocity of avian flu. Ishi notes that “overcrowding of birds in wintering areas has significantly raised the possibilities for transmission of viruses by ducks.”

The majority of new infectious diseases like COVID-19 are transmitted by animals. One is tempted to view this as a “counterattack” by humanity’s natural predator in response to the way we have continued to take the natural environment lightly.

Overcrowded and Unsanitary: The Urban Threat

The English physician John Snow, who clarified that contaminated drinking water was the source of cholera. (From the collection of the United States National Library of Medicine)

Populations around the world are increasingly concentrated in urban areas. Overcrowded city living conditions can cause spikes in infectious diseases. Beginning in the latter half of the eighteenth century, the population in England became highly concentrated in cities as a result of the industrial revolution. As more workers from the countryside flowed into these industrial centers, urban functions like housing, water systems, and garbage removal could not keep pace with the rapid change, leading to the emergence of slums. “Unsanitary, overcrowded living conditions spread infectious diseases,” Ishi points out. 

Cholera broke out in England in 1831, spreading throughout the country and claiming the lives of around 140,000 people. At the time, raw sewage flowed into the Thames River, which was the source for the city’s untreated drinking water. In 1854 the physician John Snow investigated areas with large outbreaks of cholera and found that many of those who contracted the disease were drinking water from wells that had been similarly contaminated.

Clarifying that cholera was transmitted by drinking water overturned the prevalent view that it was an airborne disease. Dr. Snow became known as the father of epidemiology, a new field of study that led to improvements in water and sewage systems.

Confined Spaces Breed Mass Infection

“The example of slave ships first made people aware of just how easily viruses can spread when people are in cramped quarters,” Ishi explains. He notes that during voyages from West Africa to the Americas, around 30% to 50% of the slaves on board would die of disease before reaching the destination. Viruses easily infect one person after another when people are concentrated in a small area.

This problem of mass infection arose on the Diamond Princess cruise ship during this year’s outbreak of COVID-19. Ishi describes what happened on board: “Around 3,700 passengers were on the ship, making it a highly concentrated living environment. On top of that, many on board were elderly—a cohort more likely to be infected—creating the optimal conditions for the virus. Outbreaks of infectious diseases often occur on cruise ships. According to a report by the US-based Centers for Disease Control and Prevention, there have been 110 cases of mass infections aboard cruise ships worldwide over the past decade.” Even the most luxurious ship can be attacked without mercy by a virus.

The Diamond Princess cruise ship, which saw a mass outbreak of COVID-19, docked at Daikoku Pier in Yokohama on February 12, 2020. (© Jiji)

China’s Heavy Responsibility

In his aforementioned book, written six years ago, Ishi pointed out that “China bears a major responsibility for the outbreak of infectious diseases.” He accurately predicted a future pandemic of the sort we are experiencing now. Under a heading titled, “China Could Be a Nest of Infectious Diseases,” he noted that the masses of tourists during the Chinese New Year, traveling within and outside the country, could spread infections. China, with a population of nearly 1.4 billion, still faces many serious public sanitation problems outside of its main urban areas.

Ishi also offers harsh criticism of Chinese development on the African continent. “area of concern is China’s business expansion in West Africa, another part of the world also lagging behind in terms of public sanitation. Huge numbers of Chinese workers have been dispatched to the area for resource-extraction projects that have hastened deforestation.”

As already noted, Africa is the source of Ebola, one of the most lethal infectious diseases of recent times. One shudders to think what might happen if the Ebola virus were brought back to China.

(Originally published in Japanese. Banner photo: Burial workers wearing protective gear carrying the body of a victim of Ebola in Beni, Congo, on July 14, 2019. © Jerome Delay/AP Photo/Aflo.)