“They can strike anywhere, anytime.  On a cruise ship, in the corner restaurant, in the grass just outside the back door.  And anyone can be a carrier: the stranger coughing in the next seat on the bus, the classmate from a far-off place, even the sweetheart who seems perfect in every way.  For whatever we go and whatever we do, we are accosted by invaders from unseen world.” – Medical writer Michael D. Lemonick in a cover story of Time magazine in 1994


Buoyed by improved sanitary conditions, advances in medical research, new vaccines, and better antibiotics, almost health officials in industrialized countries declared that the world need not worry about the scourge of communicable diseases.

In 1970, Surgeon General W. H. Stewart told the US Congress that the time had come to close the book on infectious disease.  Five years later, well-known biologist John Cairns wrote that the Western World had virtually eliminated death by infectious disease.

But like Phoenix that rises from the ashes, infectious diseases staged a comeback – deadlier, more virulent, and on a killing spree.  From time to time, new forms of previous virus emerge and create terror among human beings.

Such is the case of the novel coronavirus (2019-nCoV), which was first identified by Chinese health authorities.  The virus is associated with an outbreak of pneumonia in Wuhan City, Hubei Province. 

“Coronaviruses are a large family of viruses, some causing illness in people and others that circulate among animals, including camels, cats and bats,” the US Centers for Disease Control and Prevention (CDC).  “Rarely, animal coronaviruses can evolve and infect people and then spread between people.”

Such as has been seen with SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome).  SARS, first recognized in China, caused a worldwide outbreak in 2002-2003 with 8,098 probable cases including 774 deaths.  MERS, on the other hand, was first reported in Saudi Arabia in 2012 and has since caused illness in people from dozens of other countries.

Coronaviruses are named for the crown-like spikes on their surface.  There are four main sub-groupings of coronaviruses, known as alpha, beta, gamma and delta.  Human coronaviruses were first identified in the mid-1960s.  So far, seven coronaviruses can infect people, including 2019-nCoV.

In the beginning, many of the patients in the outbreak had some link to a large seafood and animal market, suggesting animal-to-person spread.  In Wuhan, a city in central China, vendors legally sold live animals which are butchered and eaten.  “This is where you get new and emerging diseases that the human population has never seen before,” said Dr. Kevin J. Olival, a biologist and vice president of research with EcoHealth Alliance, a nonprofit research organization, who has tracked previous outbreaks, told New York Times.

It all started before Christmas celebration.  On December 31, the WHO China Country Office was informed of cases of pneumonia of unknown cause.  By January 5, SARS and MERS were ruled out as the cause.  Four days later, preliminary investigation showed that it was a new type of coronavirus.

Then, a growing number of patients reportedly have not had exposure to animal markets, suggesting person-to-person spread is occurring. As this was occurring, President Xi Jinping admitted, in a report carried by Channel News Asia, that China was facing a “grave situation” as death toll from the coronavirus outbreak kept growing.  State-run China Global Television Network also reported that a doctor who had been treating patients in Wuhan also died from the virus.

“This time I’m scared,” admitted Dr. Yi Guan, who played an important role in tracing the development of SARS and is the director of the State Key Laboratory of Emerging Infectious Diseases at the University of Hong Kong. “Conservative estimates suggest that the scale of infection may eventually be 10 times higher than SARS,” he pointed out.

The Geneva-based World Health Organization (WHO) referred to the situation as a “public-health emergency of international concern.”  Some scientists believe that it is only a matter of time before the United Nations health agency will declare pandemic status.  This happens when it occurs over a wide geographic area and affecting an exceptionally high proportion of the population.

According to the US National Institute of Allergy and Infectious Diseases, infectious diseases are caused by tiny living creatures called germs (microbes).  They are found everywhere – in the air; on food, plants and animals; in soil and water –on just about every other surface, including the body. 

You can get infected by touching, eating, drinking or breathing something that contains a germ.  Germs can also spread through animal and insect bites, kissing and sexual contact. Vaccines, proper hand washing and medicines can help prevent infections.

Infectious agents come in a variety of shapes and sizes.  The Mayo Clinic says categories of microbes include: bacteria, viruses, fungi, protozoans and helminths.  Bacteria are one-celled germs that multiply quickly and may release chemicals which can make you sick. Some infections caused by bacteria include strep throat, tuberculosis, and urinary tract infections.

Viruses, smaller than cells, are capsules that contain genetic material, and use your own cells to multiply.  They are responsible for causing numerous diseases, including acquired immune deficiency syndrome (AIDS), common cold, genital herpes, influenza, measles, chickenpox and shingles.

Fungi, on the other hand, are primitive plants, like mushrooms or mildew.  Yeast, another type of fungus, is a necessary ingredient in most types of bread.  While some are edible, there are fungi that can cause illness.  For one, they are responsible for skin conditions such as athlete’s foot and ringworm.

Protozoans are single-celled animals that use other living things for food and a place to live.  Many protozoans call your intestinal tract home and are harmless.  But they cause diseases such as giardia, malaria and toxoplasmosis.

Helminths – which comes from the Greek word for “worm” – are actually larger parasites that include tapeworms and roundworms.  If this parasite – or its eggs – enters the body, it takes up residence in the intestinal tract, lungs, liver, skin or brain, where it lives off the body’s nutrients.  

Dr. Dennis Pirages, an American professor of International Environmental Politics in the Department of Government and Politics and the University of Maryland, consider infectious disease as a more serious threat than terrorism.

“Measured in numbers of premature deaths and associated physical sufferings, the biggest source of human insecurity, past and present is the dreaded Fourth Horseman of the Apocalypse — infectious disease,” wrote Dr. Pirages in a chapter which appeared in a State of the World Report published by Worldwatch Institute.

Infectious disease kills more people than those who perished in wars.  “Over the centuries, the number of deaths and injuries from military combat have paled in comparison to those from disease.  It is estimated that all the wars of the twentieth century killed 111 million combatants and civilians, an average of about 1.1 million a year.  Communicable diseases are now killing 14 times as many people annually.”

But despite this, relatively few resources from public treasures have been devoted to dealing with infectious disease. “Reducing the worldwide death toll from infectious disease should receive the highest priority,” Dr. Pirages urged.

Getting sick is a common experience, and most people encounters with disease organisms cause relatively little long-term damage to victims.  “Human immune systems have coevolved with a variety of potential pathogens and have developed defenses over time for dealing with most of them,” explained Dr. Pirages.

However, significant outbreaks of disease can occur.  This happens when people encounter new pathogens or new serotypes of old ones.  “But even most of these unfamiliar pathogens do relatively little damage to victims, and symptoms disappear after a few days,” said Dr. Pirages.  “Occasionally, however, virulent and debilitating pathogens emerge for which immune systems have few defenses, and fatal diseases can then move quickly through human populations.”

“The resurgence of diseases once thought to have been conquered stems from a deadly mix of exploding populations, rampant poverty, inadequate health care, misuse of antibiotics, and severe environmental degradation,” says another Worldwatch report, Infecting Ourselves: How Environmental and Social Disruptions Trigger Disease.

“Infectious diseases are a basic barometer of the environmental sustainability of human activity,” writes the report’s author, Anne Platt. “Recent outbreaks result from a sharp imbalance between a human population growing by 88 million each year and a natural resource base that is under increasing stress.”

Evidence is mounting that deforestation and ecosystem changes have something to do with this phenomenon, according to the report compiled by the Working Group on Land Use Change and Disease Emergence, an international group of infectious disease and environmental health experts.

“Many of our current activities, primarily for economic development, have some major adverse health effects,” points out Dr. Jonathan A. Patz, the lead author of the report, and a University of Wisconsin-Madison professor in the Center for Sustainability and the Global Environment (SAGE) of the Nelson Institute for Environmental Studies and the department of population health sciences.

As people remake the world’s landscapes, cutting forests, draining wetlands, building roads and dams, and pushing the margins of cities ever outward, infectious diseases are gaining new toeholds, cropping up in new places and new hosts, and posing an ever-increasing risk to human and animal health.  “The dramatic resurgence of infectious diseases is telling us that we are approaching disease and medicine, as well as economic development, in the wrong way,” Worldwatch’s Platt notes.

“One of the clearest examples of how ecosystem disruption affects disease behavior can be seen in the interaction between deforestation and the infectious, and particularly vector-borne, diseases that are common through tropics and subtropics,” writes Francesca Grifo, director of the Center for Biodiversity and Conservation at the American Museum of Natural History. (A vector is an organism that transmits a disease from place to place.)

In the 1940’s, Trinidad suffered a malaria epidemic in response to deforestation for massive cacao plantations. The plantations proved ideal for many species of bromeliad plants, 20 of which turned out to be perfect breeding sites for the local malaria-carrying mosquito Anopheles bellator.

Lyme disease, which is spread by ticks, was first identified in 1976 in the northeastern part of the United States.  “Forest fragmentation, loss of predators, and the shift of suburbia closer to woodlands were all implicated in the appearance of this disease,” said Prof. McMichael.

Another example was the Nipah virus. In 1999, this virus killed 100 people in Malaysia and nine in Singapore.  The virus was normally carried by the forest fruit bat and had not previously seemed to pass to humans.  However, because of deforestation and agricultural techniques the bat’s normal habitat and food source were changed. This forced the bats to encroach into fruit plantations, which were in close proximity to pig farms. The bats infected the pigs, which in turn infected the farmers.

“I think this has shown that deforestation has a very great impact on emergence of disease,” commented Dr. Victor Lim, a Malaysian professor of microbiology at University Hospital.

In Malaysia “and in other countries with lush tropical jungle and immense biodiversity,” continued Dr. Lim, “I am sure there are lots and lots of pathogens lurking in the jungle; they have been there for many years and they are quite happy to be there among the animals. I think things go wrong when we start to encroach into the jungle and start cutting down trees.”

Yellow fever, an acute infectious tropical and subtropical disease, was originally transmitted in a jungle cycle from monkey to monkey via the mosquito Aedes africanus. When logging started, people entered this cycle. Bitten in the forest, loggers would return to their homes in cities, where the disease would be spread in a person-to-person cycle via alternate Aedes species that thrive in disturbed urban environments.

A more global example is the AIDS virus – human immunodeficiency virus (HIV) – which some scientists think may have first infected “bush meat” hunters given access to Africa’s tropical forests by the growing network of logging roads in the continent’s interior. The disease subsequently spread by human contact and has become a global tragedy through the ability of humans to travel the world with relative ease.

In his report, Dr. Pirages wrote this conclusion: “The first step in responding to the increasing disease threat has been to use enhanced telecommunications capabilities to create more effective surveillance networks and to apply new medical expertise and technologies to task of rapidly identifying potentially diseases.  But much more remains to be done.”