News of a handful of deaths from the flu wouldn’t usually cause so much as a ripple in today’s world—unless it turned out to be the strain known as the H5N1 avian influenza, or bird flu. First recognized in 1997, the virus infected 18 people in Hong Kong, causing six deaths. Since late 2003 there have been 169 additional documented cases of the infection in humans, with 91 resulting in death. Hundreds of millions of birds—primarily poultry—have also died, either from the disease itself or through culling as a preventive measure.
So far the human cases of bird flu have been limited to China, Southeast Asia, Iraq and Turkey. Nearly every one of these people contracted the virus through direct contact with infected poultry. But scientists around the globe have warned that this virus could mutate into a strain that can be transmitted between people. Once that happens, the bird flu could spread around the world and become a pandemic within a matter of weeks: it would just take one or two infected people to board a plane headed for another continent.
The most likely way in which the virus would mutate would be if a human who had the normal flu contracted avian flu at the same time. “If both viruses—the H5N1 bird flu virus and the normal flu virus—infect the same cell, that will allow the genetic material to be exchanged. The outcome would be a new hybrid virus that can be spread directly from human to human,” explains medical doctor Thomas Monath, who is the chief scientific officer at Acambis, a vaccine development company based in Cambridge, Massachusetts.
Many comparisons have been made between the H5N1 virus and the one that caused the 1918 “Spanish” influenza pandemic, perhaps history’s most deadly flu outbreak. Scientists are concerned because H5N1 appears to be as virulent as the 1918 virus (also thought to be avian), which resulted in the deaths of anywhere from 30 to 100 million people.
“H5N1 is spreading rapidly across the world. All countries must take measures to protect human health against avian flu, and prepare for a pandemic.
“There is no time to waste.”
Presently the H5N1 avian flu is classified as endemic, meaning that it exists in just one particular region. It will be considered pandemic if the outbreak becomes global.
Of course, the avian flu is only one of a number of emerging potential pandemics. There are others too, including HIV and drug resistant strains of tuberculosis, Staphylococcus and malaria. All of these diseases are starting to infect new parts of the world and new segments of the population.
Why are so many pandemics looming on the horizon? In many ways, it’s much easier for pandemics to develop in today’s world than in the past, replies Monath. Speaking of the 1918 flu, he states, “It took 11 months for that pandemic to spread around the world. The world population was much smaller then than it is now. People traveled less, and when they did, it was by ship. The virus today would get around the world much more quickly.”
He believes four primary factors are at play: global travel, mass migration in the developing world, poverty and urbanization.
Taking to the Air
One of the biggest factors contributing to the spread of infectious diseases is air travel. Each year, according to travel industry statistics, 700 million people travel internationally—more than at any other time in history. “The world is much smaller than it used to be,” notes Jim Hughes, director of global infectious disease programs at Emory University and former director of the National Center for Infectious Diseases at the Centers for Disease Control in Atlanta, Georgia. “Today anyone can get on a plane and get to the other side of the world in a matter of 24 to 36 hours.”
The speed of travel enables an American to go on safari in Kenya, pick up the Ebola virus, fly back home to New York, pass through immigration and customs, and then spend the next few days back at work before suddenly getting sick. During the incubation period—the time between getting infected and developing clinical signs of disease—this person may expose hundreds of people to the deadly virus.
“People can be spreading disease and not even know they’re ill,” warns Hugh Pennington, president of the Society for General Microbiology in the United Kingdom and honorary professor of medicine at the University of Aberdeen’s Institute of Medical Sciences. This is quite different from the past, when people traveled by ship and it may have taken two or three weeks to travel from one continent to another. “If someone had picked up a virus before getting on the ship, he or she would have developed that disease while still onboard,” Pennington says. “Upon arrival, it would have been obvious to port authorities which passengers were sick and needed to be quarantined.”
Today, however, even the lengthiest international flights are shorter than the incubation period for most contagious diseases, making it nearly impossible to screen infected people before they get on or off a plane. “Even if passengers are exposed to a pathogen several days before leaving on a trip, and they take a 20-hour flight to a far-flung destination, they may still be in the incubation period when they arrive, and appear fine,” says David Freedman, professor of medicine at the University of Alabama. Meanwhile, those contagions will be transported to new regions.
On the March
Refugee crises are another factor relating to the spread of infectious diseases. There are around 35 million refugees and internally displaced persons in the world today, primarily in sub-Saharan Africa, the Middle East, southern Asia and Latin America. Many of these people have fled their homes because of political conflicts in their respective countries. Often they are in poor health and have traveled hundreds of miles on foot under adverse conditions, with little or no food or clean water and inadequate hygiene, picking up numerous pathogens along the way before ending up at a refugee camp, shelter or other temporary living arrangement.
Not only do refugees transport pathogens to new regions, but the refugee camps they may be living in provide ideal conditions for the proliferation of contagious diseases. “The typical refugee camp is overcrowded and has poor sanitation, and the food and water supplies may be contaminated—just what bacteria need to flourish,” Monath says. A case in point would be the tragedy following the migration of more than half a million Rwandan refugees into Zaire in 1994. Cholera and Shigella dysenteriae swept through the camps, killing nearly 50,000 people during the first month.
Steeped in Poverty
Persistent poverty has also increased the potential for disease outbreaks. “We live in an epidemiologically divided world, with increasingly large gaps between rich and poor, both among and within countries,” asserts Roy Anderson, a fellow of the Royal Society and professor of infectious disease epidemiology at the University of London’s Imperial College.
In the mid-19th century, English physician John Snow was one of the first to note the consistently higher rates of disease among the poorest working classes. He saw that the poor were often malnourished, had limited understanding of proper hygiene, had little access to medical care, and often lived in densely populated slums—just the right conditions for the transmission of diseases. Snow saw, too, that diseases spread from pockets of poverty—in the cities, factories, mines and alleys—to society at large. Anderson confirms, “Diseases among the poor become diseases, eventually, among the well-to-do.”
Not surprisingly, the poorest nations of the world have typically had the worst problems with infectious diseases. One of the most desperate regions of the world is sub-Saharan Africa. A 2004 World Bank report found that close to half the population in this region live in poverty, and the percentage is projected to increase in the years ahead. According to the report, one in every ten of the world’s poor lived in sub-Saharan Africa in 1980. By 2000, the figure had risen to one in three. The actual number of poor in that region jumped during roughly that same 20-year period from 164 million to 314 million. Less than half the population has access to safe water or sanitation facilities. And projections suggest that sometime in the next decade, one out of every two poor people on earth will live in sub-Saharan Africa.
But, warns Anderson, “this is not just a concern for Africa.” Just as diseases do not stay in the poorer parts of a town, they do not confine themselves to poorer nations. “Many of the diseases that Western nations are contending with today got their start in the developing world,” he says. Sooner or later someone visits a disease-infested area or someone from that area travels to another region, and a pathogen is transported to new territory.
Diseases can follow the increasing numbers of people, particularly in the developing world, who move from rural areas to large cities in order to find work. Many end up living in overcrowded megacities—huge urban conglomerations. If we define these metropolises as having 5 million or more residents, then there are more than 40 megacities in the world today, a large majority of them in less developed nations. In contrast, 50 years ago there were just eight, nearly all in developed countries. Some predict that by 2015 the list will include 59 cities, and of these, 48 will be in less developed nations.
Urbanization encourages the spread of contagions that may once have been obscure and localized in sparsely inhabited villages. “Pathogens like dense populations because it promotes transmission from person to person,” Anderson says. Further compounding the problem, the population of many megacities has increased too rapidly for the infrastructure to continue supporting it, and the local economies aren’t usually strong enough to finance the necessary improvements. “Sewage and water systems are often inadequate, resulting in water supplies that are tainted with deadly bacteria,” Anderson says. “There may not be enough hospitals, so when people do get sick, they cannot get the medical care they need.” Additionally, he points out, most megacities are located in tropical or subtropical regions, where infectious microbes thrive.
Three Vital Steps
Today the world anxiously wonders whether or when the avian flu will reach pandemic status. Many view television news reports of new avian flu cases and worry about when the virus will show up in their country. There have already been reports of people stocking up flu medications and vaccines “just in case.” Some health officials believe that, at the very minimum, 2 million people will die worldwide from the disease, while others predict worst-case scenarios of up to 150 million. And if that weren’t enough to be concerned about, the number of cases of HIV, as well as drug-resistant TB, malaria and staph, also continues to climb.
“We are a long way from eliminating the health threat posed by the avian flu, HIV, malaria, or a long list of other infectious diseases,” warns Monath of Acambis. What’s the answer? He points to three vital steps that must be taken if we are to get disease problems under control: improved surveillance, continued research and public education.
“The looming threat of a global influenza pandemic demands global, regional and national attention, and preparation and response to a pandemic is a shared responsibility.”
“We need to improve our surveillance on a global level,” he says. “We need to keep an extensive lookout for new or reemerging infections so the health community can develop the appropriate containment measures before diseases spread to plaguelike proportions. Nations should report outbreaks to the international community when the first cases are detected. This is something that hasn’t always happened in the past.”
Continued research is essential, Monath adds, so that the medical community can better understand the factors that foster emergence of infectious diseases, and to develop better diagnostics, treatment regimens and prevention tactics. Public education and behavioral change are also vital in order to prevent the spread of diseases through travel, poor personal hygiene, improper food handling, drug abuse and high-risk sexual behavior.
“It’s going to take cooperation and sharing of information, with every nation working together, if we are going to get these problems under control and prevent pandemics,” says Emory University’s Hughes. “Things have changed a lot in the last century. What’s a problem for one country in a remote part of the globe is a concern for the whole world. We’re all in this together.”