The rise of globalization has contributed significantly to the spread of infectious disease. As the acquired immunodeficiency syndrome (AIDS) epidemic has illustrated, a disease that emerges or reemerges anywhere in the world can 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, insects, exotic animals, or shipments of fruits, meats, or vegetables.

With globalization, diseases no longer have borders. Nations and international health organizations must work together to prevent and control the spread of infectious diseases.

Trade and travel can transmit infectious diseases. Travel is a bigger business than oil exports, food products, or automobiles, according to the World Tourism Organization (WTO). It takes less than 36 hours to travel to almost any destination on the globe, far shorter than the usual incubation period 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 American traveler Joseph Ghoson demonstrated in 2004.

Lassa fever killed Ghoson. A zoonotic, or animal-borne, disease, Lassa fever can also be spread through person-to-person contact. Transmission occurs when a person comes into contact with the blood, tissue, secretions, or excretions of an infected individual. In epidemics of Lassa fever, as many as 50 percent of infected individuals may die. When Lassa fever was confirmed as Ghoson's cause of death, the US Centers for Disease Control and Prevention (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 flight he took home from London to Newark, New Jersey. 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. It does not have electronic access to airline records or flight manifests without special arrangement. Accordingly, investigators from the CDC's Division of Global Migration and Quarantine had to fly to Newark to sift through documents to identify Ghoson's fellow travelers. There was no way to identify other people who might have come into contact with Ghoson on his trek back from Africa.

Measles has also been spread through travel. Over the Christmas holiday in 2014, a person with measles visited Disneyland in California and spread the disease to 125 others in seven other states. Eighty-four of the affected people were hospitalized. The source of the initial Disney exposure could not be identified, but the strain of measles had caused a recent outbreak in the Philippines and could be found in at least 14 different countries in the six months prior to the incident.

International visitors from countries where measles is endemic can expose others to the disease in any place where people gather, such as airports and other tourist attractions. In 2018 an Australian tourist spread measles throughout several hotels and a museum in New York City. Measles, which can kill, is highly contagious, but high vaccination rates usually protect Americans from the disease. In 2013 an outbreak in New York City affected an Orthodox Jewish community that did not support vaccination. The 57 people who became ill were linked to an unvaccinated person who had caught measles while traveling in London. Both Australia and England have high vaccination rates, so the initial sources for both episodes may be other travelers who remain unidentified.

At an airport in Kunming, China, officials take part in measures designed to control the spread of SARS, an infectious disease that spread around the world in 2003. © Travel Ink/Getty Images © Travel Ink/Getty Images

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 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.

The CDC has revised its infectious disease priorities in response to globalization. International outbreak assistance is now a top priority. The CDC has strengthened its diagnostic facilities and enhanced its capacity for epidemiological investigations overseas. The CDC offers 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. For example, the CDC has worked in West Africa to fight the Ebola epidemic that began in 2014. Transmission of the virus apparently stopped in 2016, but the CDC established a surveillance system to monitor the region in the event that Ebola reappears. Ebola killed about 40 percent of the people who were infected, making it particularly terrifying.

The CDC also 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 the US 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 lists of passengers for longer periods. However, legislative success has been limited.

The CDC also expanded 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 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 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, whereas animal diseases are addressed by the US 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. CDC preparations for a pandemic include avian influenza because the risk is so high.

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. 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 but endemic in underdeveloped 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 a 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 fever. Both illnesses were extremely rare in the United States, typically occurring only in people who traveled abroad. 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 substantial populations across the United States. The Aedes albopictus mosquito, associated with dengue virus, is found in varying numbers in Hawaii and throughout the southeastern United States. Researchers tracked a sharp increase in the presence of daytime 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. Page 386  |  Top of ArticleHealth 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.

CDC Travel Notice: MERS in the Arabian Peninsula

SOURCE: “MERS in the Arabian Peninsula.” Centers for Disease Control and Prevention, June 28, 2017. https://wwwnc.cdc.gov/travel/notices/alert/coronavirus-saudi-arabia-qatar (accessed February 28, 2018).

INTRODUCTION: The US Centers for Disease Control and Prevention (CDC) is responsible for issuing travel notices to warn international travelers about health issues they may face in the countries to which they are traveling. The CDC has three levels of notice: Warning Level 3 (Avoid Nonessential Travel), Alert Level 2 (Practice Enhanced Precautions), and Watch Level 1 (Practice Usual Precautions). The following is an Alert Level 2 notice regarding an outbreak of Middle East respiratory syndrome (MERS) in the Arabian Peninsula. The notice describes the outbreak and outlines precautions that travelers should take when visiting the region.

June 2017

As of June 2017, nearly 2,000 cases of MERS (Middle East Respiratory Syndrome) have been identified in multiple countries in the Arabian Peninsula, including in travelers to the region. In about one-third of the cases, the patients have died. For more information, see CDC's MERS website.

It is not clear how people are exposed to MERS coronavirus, which causes MERS. However, evidence of transmission to humans from direct contact with camels has been steadily increasing. Most instances of person-to-person spread have occurred in healthcare workers and other close contacts (such as family members and caregivers) of people sick with MERS.

CDC does not recommend that travelers change their plans because of MERS. If you are concerned about MERS, you should discuss your travel plans with your doctor.

MERS is a viral respiratory illness first reported in Saudi Arabia in 2012. The virus that causes MERS is different from any other virus that has been previously found in people. Symptoms of MERS include fever, cough, and shortness of breath. CDC is working with the World Health Organization (WHO) and other partners to understand the public health risks from this virus.

All travelers can take these everyday actions to help prevent the spread of germs and protect against colds, flu, and other illnesses: