Infections Spread Across A Shrinking Globe
Ebola grabs its victims like a leopard hungry for a kill and voraciously sucks life from its prey. Last February, an African woman who boarded a connecting flight to Toronto at Newark Airport became seriously ill during the flight with some of the symptoms of Ebola hemorrhagic fever. Full blown Ebola is characterized by high fevers, exhaustion, severe head, stomach and chest pains, and widespread oozing of blood, with the majority of those affected dying within two weeks. The virus is named for a river in the Democratic Republic of the Congo in Africa, where it was first recognized. So far, the disease has struck only in Africa.
The news spread quickly that Ebola might have landed in the Garden State, and some New Jerseyans panicked. Public health authorities cautiously monitored events, but tests rapidly confirmed that the woman was not infected with this deadly virus. Although state residents breathed a collective sigh of relief, the questions remain: Is it time to worry? Can this virus jump continents and take a foothold in this country?
An epidemic represents an increase in the occurrence of a disease beyond usual expectations. Epidemics that mushroom to affect a large number of people in multiple areas are termed pandemics. Some of the most devastating pandemics in human history were the Black Plague of the Middle Ages, influenza in 1918 and, most recently, AIDS, which is now killing millions of people yearly.
An epidemic of a bacterial or viral pathogen can be spurred in many ways, such as: 1) an animal or insect picks up disease organisms from a source of infection, such as blood, and later deposits them, infecting a new host; 2) a single infected human, perhaps not yet symptomatic, comes in intimate contact with others; 3) deficiencies in sanitation and hygiene increase exposure to bodily fluids; 4) social customs increase bodily fluid contact; and 5) the health care system infrastructure (hospitals, staff, equipment) is inadequate.
Could Ebola make its way here? Its not likely, says Stanley H. Weiss, MD, (left), associate professor of preventive medicine and community health at UMDNJ-New Jersey Medical School (NJMS). Ebola occurs in small localized outbreaks in developing countries, and healthy people do not harbor the virus. Scientists believe the first person contracts the infection from an animal host, perhaps a primate or a mammal. From there the disease is generally spread in a health care setting or during burial of bodies infected with the virus.
"Because Ebola immobilizes its host quickly, its not easy for it to spread beyond the initial local outbreak even though it is highly contagious," says Weiss, who is also an associate professor of quantitative methods at UMDNJs School of Public Health (SPH). "Contrast it to HIV, an insidious virus that typically infects its victim silently for years without producing symptoms, all the while having the capability to be transmitted by intimate contact."
But its not impossible that a person might board a plane before becoming deathly ill, perhaps deliberately seeking advanced medical care in the U.S., and begin spreading the disease to others especially before its been diagnosed. The job of public health specialists at the Centers for Disease Control and Prevention (CDC) and state health departments is to assist with identification, monitor the situation and implement appropriate control measures to minimize an outbreak. What are some of the infections currently capturing the attention of U.S. surveillance teams?
STOPPING GERMS IN THEIR TRACKS
Globalization is the buzz word of our times; and frequent and far-reaching travel is its primary fuel. Add to that an international market for food and medicines and destruction of natural habitats, and you will begin to understand how a germ can be set loose from a jungle in South America and find its way to your doorstep.
"Mathematically, we can predict what fraction of a population needs to be protected to prevent the spread of an infectious disease," says Weiss. "But sometimes the immunity levels fall, and we lose what is known as herd immunity, the ability of a group or community to resist a disease after an infectious agent has been introduced."
Take measles, for instance. In 1985 and 86, Jersey City was the site of a serious outbreak of the disease, 15 years after the MMR vaccine was licensed in this country. When this highly contagious childhood infection was brought back into the U.S. by unvaccinated foreign-born children, there was a pool of susceptible youngsters without immunity and it spread efficiently and quickly, especially among pre-schoolers.
Surveillance is the critical tool for controlling the spread of infectious disease. According to the CDC, surveillance systems provide for the ongoing collection, analysis and dissemination of data to prevent and control disease. Data is used to identify cases to further investigate, to estimate the magnitude of a health problem, to detect outbreaks and generate appropriate interventions, to monitor changes in infectious agents, to facilitate research, to detect changes in health practices, and to aid in planning for future resources and policies.
Weiss cites the emergence of West Nile virus in the metropolitan region as resulting in part from a breakdown of good public health surveillance in New York. "The West Nile outbreak came as a surprise because funding cutbacks led to inadequate surveillance of mosquito populations in New York," he says.
This virus was isolated in the West Nile District of Uganda in 1937, and the first recorded epidemics occurred in Israel during the 1950s. It cropped up in the U.S. in 1999, causing fatal encephalitis in humans and horses and death in some domestic and wild birds. Although no one is certain how it entered this country, experts think that it came by way of infected mosquitoes, illegally imported birds or perhaps, in infected birds that migrated here. The infected mosquitos and birds have since crossed state lines from New York to New Jersey.
Although dead crow reports made the news on a daily basis last summer, many health experts believe the attention is overblown, and that surveillance efforts will keep the virus in check. Leah Ziskin, MD, MS, (left), points out that New Jersey has maintained mosquito commissions, which are the first defense against mosquito-borne illnesses. "Our local public health departments get good marks here," says Ziskin, who is associate dean of the Stratford/ Camden campus of SPH.
TB AND THE RUSSIAN CONNECTION
Tuberculosis (TB) resurfaced in this country in the 1980s, primarily in urban communities. The HIV/ AIDS epidemic and increased immigration from countries where TB rates are high both contributed to the disease gaining a foothold once again, and spawned more dangerous, drug-resistant variants.
But it is now under control in this area due to the watchfulness and swift action of medical personnel, according to Jerrold Ellner, MD, (left), director of the Center for Emerging and Re-Emerging Pathogens at NJMS. He says that 97 percent of all cases worldwide occur in developing countries. Hot spots include Africa, India, the former Soviet Union and the Republic of China.
"In general, those at risk in New Jersey include people in close contact with recent immigrants, prison populations and hospital workers," says Ellner, who is also acting chair of medicine at NJMS. He notes that all staff of UMDNJ-University Hospital are tested once yearly for TB.
The Center for Emerging and Re-Emerging Pathogens was created to recruit leading scientists who are studying infectious diseases that are increasing in frequency or becoming drug-resistant, and to provide them with the biocontainment facilities necessary for their work. Tuberculosis, HIV/AIDS, Lyme disease and potential agents of bioterrorism, such as anthrax, are being investigated.
Ellner, who has been involved in TB research for 25 years, points out that New Jersey is not yet ready to close the book on tuberculosis. Many immigrants from the former Soviet Union and eastern Europe are settling in Jersey City and Union City, and may be infected with the bacillus that causes the disease.
MAD COWS AND OTHER ASSORTED BEASTS
We eat a lot of products that come from cows. In addition to the obvious favorites like cheeseburgers, steaks, hot dogs and meatballs, we consume or utilize many other cow-derived products such as gelatin, which finds its way into gummy bears, vitamin capsules and cosmetics, to name just a few. Should we be worried that mad cow disease will jump across the Atlantic? Experts say it could certainly be headed our way.
Mad cow disease (bovine spongiform encephalopathy or BSE) has killed more than 200,000 cattle since it first cropped up in Great Britain in 1984. It has also spread to several other European countries. Over the past eight years, a human form of mad cow disease has killed more than 80 people, many of them young. This neurologic disease is called nvCJD, or new variant Creutzfeldt-Jakob disease. Its believed to be contracted through eating the meat of an infected cow, even if the meat has been well cooked. No one has ever gotten the disease from milk or cheese.
Both the human and bovine forms of this fatal brain disease have long incubation periods; and both seem to be caused by the same agent, a virtually indestructible protein called a prion. It is not known whether BSE is carried in the blood and blood products of infected cattle.
Of major concern is bovine serum albumin (BSA), a processed component of cows blood that has been used as a growth medium for cell cultures in laboratories all over the world. BSA derived from cattle in Great Britain has now been banned from use in the U.S., but many questions remain. Might BSA used years ago during the long development process of some pharmaceuticals have been contaminated? How about nutritional supplements which can contain gelatin and other cattle-derived substances, and which are not regulated by the FDA? Could processed meal or pet food containing contaminated cow products have found their way into this country? What has surfaced so far in Great Britain could be just the tip of an enormous and slow-moving iceberg.
Worrisome as this might be, Weiss is more concerned about xenotransplantation, the transfer of tissues, blood, organs or byproducts from animals to humans. Thousands of people die each year waiting for a kidney, heart or liver. However, the public health expert says a look at HIV and the 1918 flu pandemic raises reasons for caution and concern, as does our evolving knowledge of agents such as endogenous retroviruses, and should give the medical communities enough reason to ban the breeding of primates for their organs. We are still struggling to develop regulations that balance the theoretical risks to public health versus the medical benefits for those who need replacement organs to survive.
"Xenotransplantation brings great risks for new or re-emerging diseases which could attack whole populations," Weiss says. Developmental efforts to raise pigs and perfect transplantation methodology are speeding ahead.
Investigators think that the virus now called HIV jumped from primates to humans in Africa, and that the flu epidemic of 1918 which killed 20 million people most likely evolved from flu viruses passing from chickens to pigs to people. Although the influenza virus can live complacently in animal hosts, their crossover into the human population called a zoonosis can have catastrophic consequences.
While many infectious killers such as polio and measles seem to be well under control, there are new or newly discovered infections such as Mad Cow disease that may be getting a little too close for comfort. "Globalization" has opened up the world in many new and thrilling ways, but it seems to carry on its wings the threat of more potent and widespread epidemics of infectious disease than we can even imagine.
ADVANCE OF THE SUPERBUGS
Medicine had made tremendous progress in controlling infectious disease until a few years ago. But bacteria have the ability to mutate, or change form; and many have become resistant to the powerful drugs that once killed them.
Experts blame overuse and misuse of these drugs for the problem. According to the CDC, about 50 million of the 150 million prescriptions written each year for antibiotics are unnecessary. Patients often demand an antibiotic when they visit a doctor, and also frequently stop using it when they start to feel better. Sometimes physicians prescribe a strong, broad-spectrum antibiotic that can wipe out a number of different bacteria, instead of one that specifically targets the infectious microorganism. A wait-and-see attitude often makes good sense, especially for conditions likely due to viral rather than bacterial infections.
Penicillin the miracle drug discovered in the 1940s was able to knock out almost all staph (Staphylococcus aureus) infections, which can cause some serious and potentially fatal diseases such as pneumonia, meningitis, toxic shock, heart valve and bone infections. (Many staph infections are relatively simple, like a boil.) Currently in the U.S., 90 percent of staph strains are resistant to some antibiotics; and there are strains of other bacteria resistant to all antibiotics.
Thirteen percent of this countrys two million hospital infections each year are caused by staph, according to the CDC. Hospital infections kill 60,000 to 80,000 people yearly. Vancomycin, a powerful antibiotic used for resistant infections, is losing its grip. For example, an estimated 18 to 20 percent of enterococci, bacteria living in the intestinal tract that can invade other parts of the body, are currently vancomycin resistant.
Researchers continue to devise more potent drugs in the battle against the superbugs, but unfortunately, these bugs cunningly continue to outwit them.
The magazine of the University of Medicine and Dentistry of New Jersey