Salmonella and E. coli
This year's big foodborne threat is killer tomatoes. Two years ago, spinach up and vanished from grocery store shelves around the country. Michael Pollan will be the first to tell you why: "Eighty percent of America's beef is slaughtered by four companies, 75 percent of the precut salads are processed by two and 30 percent of the milk by just one company." The consolidation of the industrial food supply necessarily means that any pathogen which enters the system will have no trouble finding its way to your dinner plate, heedless of global distances.
Compounding that problem, we have the issue of antibiotics being administered as a preventative measure in livestock and poultry. Animals are routinely fed these medicines as part of their diet, whether they are sick or not. This indiscriminate use has undoubtedly led to a reduced efficacy of antibiotics in humans. Dr. Arjun Srinivasan, a medical epidemiologist with the CDC, notes that we don't know whether overuse of antibiotics in humans is ultimately worse than overuse in animals, but that "there are those who say, if you look at the absolute amount of antibiotics that are used in animals, [it] vastly outweighs the amount that's used in humans. So therefore, that may actually be a larger component" of the problem.
trouble finding its way to your dinner plate, heedless of global distances.Compounding that problem, we have the issue of antibiotics being administered as a preventative measure in livestock and poultry. Animals are routinely fed these medicines as part of their diet, whether they are sick or not. This indiscriminate use has undoubtedly led to a reduced efficacy of antibiotics in humans. Dr. Arjun Srinivasan, a medical epidemiologist with the CDC, notes that we don't know whether overuse of antibiotics in humans is ultimately worse than overuse in animals, but that "there are those who say, if you look at the absolute amount of antibiotics that are used in animals, [it] vastly outweighs the amount that's used in humans. So therefore, that may actually be a larger component" of the problem.
Yellow Fever Virus
The first of two agents on our list spread by the Aedes mosquito, the yellow fever virus wasn't been much of a concern in the latter half of the twentieth century. Malaria control efforts in the 1950s successfully decimated the Aedes population, and with it the occurrence of yellow fever. In the past few decades, however, the mosquito has returned and is ranging much further than previous generations. It's also making its way into urban environments, which it has done in the past—an outbreak nearly wiped Memphis off the map in 1878—but in recent memory, it has been confined to the tropical jungles.
The fever gets its name from the jaundice it can cause after a few days of infection. Later comes internal bleeding (it's a hemorrhagic fever like Ebola and Marburg) followed by bloody vomit with the consistency of coffee grounds. What is most worrying about its return to cities is that it achieves a higher mortality rate among dense, unexposed populations—up to 30 percent. Recent outbreaks in Paraguay and the Ivory Coast have health officials racing to vaccinate as quickly as possible. While an effective vaccine exists, there is no treatment and no cure.
Shanghai SARS Alert
Nobody used to pay much mind to the coronaviruses. While the genus is home to two species responsible for the common cold, they haven't received the attention given to other cold-causing viruses because coronaviruses are difficult to grow in a lab environment. That all changed very quickly in 2003 when a new respiratory disease began killing doctors and nurses and showing the potential to spread at pandemic levels was identified as a previously unknown coronavirus. The infection was severe acute respiratory syndrome, or SARS, and it held the world's attention for just under a year before it disappeared in the summer of 2003.
The global public health response was a near-unparalleled success. Within weeks, control efforts led by the World Health Organization had identified a totally novel agent, devised a diagnostic test, and instituted plans for quarantine and isolation. It is undoubtedly a result of those efforts that the outbreak was contained before it could reach pandemic levels.
And while it is no longer topping watch lists, two questions persist: how did it get to humans and where did it come from? As Dr. Scott Dowell, head of the CDC's Global Disease Detection Program explains, "how it is that one of these animal pathogens acquires the ability to spread efficiently among humans is something that we don't do a very good job explaining or predicting."
Coronaviruses are known to mutate rapidly, so there may have been some biological basis to its sudden appearance and virulence, but it was still very much a surprise. Where it currently lies in wait is even more of an unknown. There is evidence the 2003 outbreak originated in a wildlife market in southern China, but the exact species of animal from which it came is still very much in contention.
Liver Infected With Ebola
This hemorrhagic fever has gained a special notoriety for being a quick and exceptionally deadly killer. Ebola is known as the fever that kills with a million cuts, because it causes a reaction in the blood that produces microscopic holes in the capillary walls. The patient then bleeds to death internally. Mortality can be as high as 90 percent. It is invariably a headline-grabber when outbreaks strike. But it's not on this list because it's presently a significant threat (it's not). It's here for two reasons.
The first has to do with a trait Ebola shares with the SARS coronavirus—its zoonotic host is a mystery. Although the virus has been known to us since the mid-1970s, we are still largely in the dark about what its reservoir is in nature. Even after a comprehensive study of tens of thousands of animals in outbreak regions, no virus was found. That points to the difficulty public health officials face when unknown threats emerge—we have a very hard time tracking some viruses we've known about for decades, so you can imagine the mounting complications when starting from zero.
The second reason it's on this list is to place it within the context of the rest of the agents. While it is a ravaging disease, it presents little threat outside of where it appears locally. It is not communicable through the air, and only spreads from person to person; often because of poor hospital conditions in the areas in which it appears. In addition, it presents symptoms very quickly—infected persons are likely to be isolated before getting very far. All the rest of the diseases on this list can spread far and wide, which makes them much more threatening.
The first has to do with a trait Ebola shares with the SARS coronavirus—its zoonotic host is a mystery. Although the virus has been known to us since the mid-1970s, we are still largely in the dark about what its reservoir is in nature. Even after a comprehensive study of tens of thousands of animals in outbreak regions, no virus was found. That points to the difficulty public health officials face when unknown threats emerge—we have a very hard time tracking some viruses we've known about for decades, so you can imagine the mounting complications when starting from zero.
The second reason it's on this list is to place it within the context of the rest of the agents. While it is a ravaging disease, it presents little threat outside of where it appears locally. It is not communicable through the air, and only spreads from person to person; often because of poor hospital conditions in the areas in which it appears. In addition, it presents symptoms very quickly—infected persons are likely to be isolated before getting very far. All the rest of the diseases on this list can spread far and wide, which makes them much more threatening.
Methicillin-Resistant Staphylococcus Aureus
Methicillin-resistant Staphylococcus aureus,—or MRSA,—is a mutant variant of the common staph infection found in hospitals and nursing homes. What sets it apart from common staph is its resistance to a wide range of commonly used antibiotics. In the late 1990s, it began to appear in people who hadn't been anywhere near a health-care institution. They were struck with what scientists have taken to calling Community-Associated MRSA. The disease appears in places where daily, close contact is the norm: schools, day-care centers, and prisons, for example. If caught early, before it gets into the bloodstream, it is usually treatable with low-grade antibiotics, and its spread can be controlled. It may even be remedied without antibiotics by draining the lesions it raises on the skin. Once it passes that early stage, however, it can become a much more difficult infection to eradicate.
MRSA is an important warning sign because doctors are frequently having to use the strongest antibiotics to treat it. We know this to be an effect of antibiotic overuse. The end result is a breed of bacteria against which we have little, if any recourse for a cure. "The challenge that we'll face is that a growing number of bacterial infections will be more and more difficult to treat. The reports are rare, but we're already seeing [cases] of bacteria... where there are no effective antibiotics to treat the infection," says Dr. Srinivasan. Right now, these cases are appearing only in hospitals and only in the most immunocompromised patients, but that was once the case for drug-resistant staph, too.
The only real, immediate course of action is education and vigilance about proper antibiotic use, because, as Dr. Srinivasan notes, "our ability to develop new drugs has already been surpassed by the speed with which bacteria are developing resistance." Several institutions have undertaken awareness campaigns, like the CDC's "Get Smart" program and the Infectious Diseases Society of America's "Bad Bugs, No Drugs," both of which have had good success educating both patients and health-care workers.
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