Globalization and Infectious Disease
Globalization and Infectious Disease
The rise of globalization has contributed significantly to the spread of infectious disease. As the AIDS epidemic has illustrated, a disease that emerges or re-emerges anywhere in the world can now move rapidly around the globe. With the increased ease of air travel and the growth of international trade, infectious diseases have more opportunities to spread than in previous eras. Dangerous microbes (pathogens) can arrive in people, in insects, in exotic animals, or in shipments of fruits, meats, or vegetables.
With globalization, diseases no longer have borders. Nations and international health organizations must now work together to prevent and control the spread of infectious diseases.
Trade and travel can transmit infectious diseases. More than 760 million people travel internationally each year, according to the World Tourism Organization. It takes less than 36 hours to travel to almost any destination on the globe—far shorter than the usual incubation periods for most infectious diseases. A person can become infected in Sierra Leone, travel through Europe, and die in the United States within the space of a few days, as the American traveler Joseph Ghoson demonstrated in 2004.
Lassa fever, a zoonotic or animal-borne disease, can also be spread through person-to-person contact. Transmission occurs when a person comes into contact with blood, tissue, secretions, or excretions of an infected individual. In epidemics of Lassa fever, as many as 50% of infected individuals may die. When Lassa fever was confirmed as Joseph Ghoson's cause of death, the Centers for Disease Control (CDC) rushed to compile a list of 188 people known to have had contact with him while he was infectious. They included five family members; 139 health-care workers at the hospital where he died; 16 employees of commercial laboratories in Virginia and California, where Ghoson's blood samples were tested; and 19 people on the London, England, to Newark, New Jersey, flight that he took home. If infected, these individuals could spread Lassa fever.
The CDC could not locate every person who had contact with Ghoson in part because of reporting problems. The CDC does not have electronic access to airline records and or flight manifests without special arrangement. Accordingly, investigators from the CDC's Global Migration and Quarantine unit had to fly to Newark and sift through paper documents to identify Ghoson's fellow travelers. There was no way to identify other people who may have come into contact with Ghoson on his trek back from Africa.
The exact scope of infectious diseases spread through globalization is unknown. Many cases probably go unreported each year because surveillance is passive. Physicians must recognize a disease, inquire about the patient's travel history, obtain proper diagnostic samples, and report the case. A physician who does not expect to see an illness that is rare or unknown in his country could misidentify the disease.
Additionally, inspections of cargo are declining even as imports, legal and illegal, increase. Monkeypox is a zoonotic, or animal-borne, disease that first appeared in the United States when contaminated African rodents that had been imported into the country were housed next to prairie dogs. The virus passed from the prairie dogs to humans in 2003 after the animals were sold as pets. Tens of thousands of exotic animals are smuggled into the United States each year as part of a global black market. Meanwhile, the globalization of food production has created a boom in food import and export without an accompanying rise in inspectors. However, an infected insect or small animal in a corner of a large crate might elude even the most eagle-eyed official.
WORDS TO KNOW
EMERGING INFECTIOUS DISEASE: New infectious diseases such as SARS and West Nile virus, as well as previously known diseases such as malaria, tuberculosis, and bacterial pneumonias that are appearing in forms that are resistant to drug treatments, are termed emerging infectious diseases.
PATHOGEN: A disease causing agent, such as a bacteria, virus, fungus, etc.
VECTOR: Any agent, living or otherwise, that carries and transmits parasites and diseases. Also, an organism or chemical used to transport a gene into a new host cell.
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
The CDC has revised its infectious disease priorities in response to globalization. International outbreak assistance is now a top priority. CDC plans to strengthen its diagnostic facilities and enhance its capacity for epidemiological investigations overseas. The CDC expects to offer follow-up assistance after infectious disease outbreaks as part of an effort to control new pathogens. It has also increased research on diseases that are uncommon in the United States. The CDC launched the International Emerging Infections Program, targeting disease sources in developing countries and working with international health organizations to prevent the spread of disease through travel, migration, and trade. It is also coordinating disease control and eradication efforts to stop the spread of malaria and tuberculosis.
The CDC is also attempting to strengthen preventive procedures at home. Prompted in part by the SARS epidemic of 2003 and the Ghoson incident, the CDC has asked Congress to toughen laws on disease reporting, increase the number of inspectors and quarantine stations, and require common carriers such as airlines and ships to maintain list of passengers for longer periods of time.
The CDC is also promoting the expansion of regional disease surveillance networks into a global network that could provide early warning of infectious diseases. With this strategy, the CDC works closely as a technical consultant with the World Health Organization (WHO). Like the CDC, WHO is charged with addressing health threats in the changing global landscape and it has focused on creating new strategies to coordinate response efforts.
Coordination is the major issue that faces government agencies as they attempt to protect the public health. The CDC's Geographic Medicine and Health Promotion Branch has warned that there is inadequate national surveillance for zoonotic diseases. Human diseases are handled by the CDC, while animal diseases are addressed by the Department of Agriculture. Monkeypox is just one example of a zoonotic disease that has infected humans. Avian influenza, also known as H5N1, or bird flu, is a zoonotic disease that has the potential to cause enormous disruptions around the world. In 2005, World Bank economists forecast that a H5N1 pandemic could cost the global economy about 2% of the annual gross domestic product.
Vaccines offer a promising means of stopping infectious disease. Under the long-established WHO system, countries send influenza specimens to the agency, which then makes these samples available to the global community for public health purposes, including vaccine development. However, some developing countries have been reluctant to share viral samples for vaccine research because they want to ensure that their citizens have access to vaccines at affordable prices. Indonesia, the nation struck hardest by H5N1, announced in 2007 that it would not send human bird flu virus samples to WHO unless the agency could guarantee the specimens would not be used commercially. Indonesia and WHO subsequently came to an agreement that Indonesia would continue to send samples while WHO will stockpile vaccines in the event of an epidemic. A long-term WHO goal is that developing countries obtain enough technology and scientific training to produce vaccines.
Globalization also has positive effects for combating disease. Pharmaceutical companies have reached agreements with several nations and international health organizations to provide drugs and vaccines for some epidemic diseases at reduced cost. Increasing international attention on neglected diseases has garnered support for research and development of drugs and vaccines to fight illnesses rare in industrialized nations, are but endemic in under-developed nations. International agencies are better able to communicate vaccine and drug needs. Finally, an increasing amount of companies are producing vaccines and manufacturing therapeutic drugs in growing number of nations—India is poised to become one of the world's major suppliers of pharmaceuticals in the next several decades.
Increase in worldwide trade has posed unique challenges for disease prevention. In 1986, CDC investigators began an investigation of rising numbers of certain Asian mosquitoes in the United States. The invasive species served as vectors (transmitters) of disease, causing illnesses such as West Nile and dengue (DEN-gay) fever. Both illnesses were extremely rare in the United States, typically occurring only in people who traveled abroad. The CDC researchers discovered that ports of entry in California, Florida, New York, and Texas all had sizable populations of daytime biting mosquitoes native to Asia. Cargo ships were identified as the means of transport—especially those ships carrying large box containers or old tires.
To combat invasive species and vectors of disease, there are now more stringent laws governing inspection, decontamination, and quarantine of imported cargo. However, several invasive species have managed to establish sizable populations across the United States. The Aedes albopictus mosquito, associated with dengue virus found in varying numbers from Hawaii throughout the southeastern United States. Researchers tracked a sharp increase in the presence of day-biting mosquitoes to shipments of bamboo plants to California plant nurseries. Immediate control measures such as insecticide application and quarantine and decontamination of other shipments prevented the mosquitoes from establishing large local populations. Health officials warned nursery workers to use insect repellant and wear covering clothing to minimize the risk of bites. No cases of illness were linked to the event. Preventative measures have worked to combat similar cases of invasive mosquito species in 2004 and 2006.
Airline travel can provide a vehicle for spreading infectious diseases. In June 2007, the first federal isolation order in the United States in over forty years was issued to traveler Andrew Speaker from Atlanta, Georgia, when he returned to the United States after boarding planes in Georgia, Italy, and France while he was infected with a highly resistant strain of tuberculosis. Although no active tuberculosis infections among Speaker's fellow travelers have been found, another case of air travel in 2003 by an infected person did result in spreading the newly-emerging disease known as SARS. In the following New York Times article, journalist Kieth Bradshear relates how SARS spread from one infected man to fellow passengers on a flight from Hong Kong to Beijing in 2003. Bradshear has been the Hong Kong Bureau Chief for the New York Times since 2001.
Centers for Disease Control and Prevention. Protecting the Nation's Health in an Era of Globalization. Atlanta: Office of Health Communication, National Center for Infectious Disease, Centers for Disease Control and Prevention, 2002.
Wamala, Sarah P., and Ichiro Kawachi. Globalization and Health. New York: Oxford University Press, 2006.
Centers for Disease Control and Prevention. “Lassa Fever.” December 3, 2004 <http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/lassaf.htm> (accessed May 17, 2007).
Caryn E. Neumann