Immigration and Infectious Disease
Immigration and Infectious Disease
Disease History, Characteristics, and Transmission
Introduction
Every day, an estimated two million people cross an international boundary. Many of these people are simply travelers who have planned short visits. Others are immigrants, either refugees or voluntary migrants. Some migrants never cross national borders but are displaced within their own nations. As of 2007, there are an estimated 25–45 million internally displaced persons (IDPs) worldwide. IDPs typically migrate or are forced to move because of war, ecological disaster, disease, or economic collapse. This increasing movement of people across the globe plays a significant role in the spread of disease.
Since antiquity, health hazards have moved across long distances through movement of people. Travel, trade, exploration, and war forged nations but also spread disease. Travel by horse or on foot was slow, serving as a limited barrier to the transport of infectious disease—those who fell ill often died or were no longer ill by the time they reached other population centers. Ships spread diseases faster as a disease could linger on ship for months, infecting whole crews. Also, the large cargo load of ships posed a unique disease risk. In the case of the Black Death (plague), rats aboard cargo ships likely hosted fleas responsible for spreading plague throughout Asia, the Middle East, and Europe. In the modern era, the spread of air travel and its reduced costs have greatly increased the number of travelers as well as heightened the risk of disease. Air travel permits infected persons and diseases to reach new populations—often in distant locations—within hours.
Immigration raises many of the same disease issues as voluntary travel. However, immigrants also have unique health needs. Some immigrant populations come from areas with parasites or other infectious diseases that are endemic to their homeland, but have been eliminated in the industrialized world. Immigrants may not have had access to routine healthcare in their home countries. Providing effective healthcare to immigrant groups requires training healthcare professionals to recognize the health needs of diverse immigrant groups.
Disease History, Characteristics, and Transmission
Cholera, dysentery, typhoid, tuberculosis, HIV/AIDS, and malaria are only a few of the infectious diseases that migration and immigration have helped to spread. Illnesses that have been largely eliminated from some areas, such as malaria or tuberculosis, can be reintroduced by migrants, and such cases of disease are labeled imported cases.
Cholera, dysentery, and typhoid are major killers that are spread by poor sanitation. Densely packed refugee camps with improper sanitation and poor hygienic conditions foster outbreaks of infectious disease. In 2007, one person died and 30 others were hospitalized after a cholera outbreak at a Congolese refugee camp in Uganda. The refugees were subsequently advised by Ugandan officials to observe precautionary measures like washing hands, avoiding raw foods, and using clean utensils. These measures, as well as construction of latrines, helped reduce some incidence of infectious disease. Such measures are not always possible at severely under-resourced, overcrowded, and hastily constructed camps. Food shortages and malnutrition in refugee and IDP camps also contribute to the spread of disease.
Scope and Distribution
It is difficult to measure the scope and distribution of infectious disease spread by immigrants because of reporting difficulties. Health care systems in some countries, including developing nations that have received large numbers of refugees from neighboring nations, are too inadequate to correctly identify diseases and complete the necessary procedures for effective reporting. However, the Centers for Disease Control (CDC) and the World Health Organization (WHO) have helped identify areas of concern.
Haiti has sent large numbers of economic and political refugees to the United States and to other Caribbean nations. In 2006, the Jamaican Health Ministry reported that there was a link between Haitian immigrants and a recent outbreak of malaria in Jamaica. DNA testing by the CDC tied an outbreak in Kingston to a single source consistent with the Falciparum malaria parasite found in Haiti. At least 302 Jamaicans were infected. The government conducted an island-wide surveillance of breeding sites for the Anopheles (malaria-spreading) mosquito and destroyed about 450 Anopheles breeding sites in 256 communities.
Tuberculosis, an infectious disease that in some forms is resistant to treatment, is spread through air droplets expelled when infected persons cough, sneeze, speak, or sing. It had largely been eliminated from some nations, notably the United States and the United Kingdom, until immigration brought it back. In 2001, 61.4% of all tuberculosis cases in the Netherlands occurred among foreign citizens. Tuberculosis transmission during air travel has been documented by WHO.
Varicella, the chickenpox virus, is yet another disease that can be spread by immigrants. In tropical countries, varicella does not generally infect in early childhood as it does in temperate zones. In the tropics, infections typically occur in the late teens and 20s, meaning immigrants from those countries don't have the same high level of immunity to chickenpox as do young adults who grew up in temperate countries.
Treatment and Prevention
The International Health Regulations (IHR), a WHO-designed legal instrument, aims to provide maximum security against the international spread of diseases with a minimum interference with world traffic. The first IHR, approved in 1969, only targeted cholera, yellow fever, and plague. The rise of globalization prompted a revised IHR, which took effect on June 15, 2007. Among its many measures, the IHR establishes a single code of procedures and practices for routine public health measures at international airports and ports and some ground crossings. The regulations focus on ensuring early detection, confirmation, investigation and rapid response for any emergencies of international concern.
However, some nations are having difficulty with the IHR. As the deadline for the enforcement of the IHR approached, Kenya's borders continued to be frontiers for the spread of communicable diseases. Meanwhile, an unprecedented resurgence of communicable diseases such as tuberculosis, malaria, avian influenza, and SARS is causing international concern. Kenya, as one example, reported outbreaks of polio and Rift Valley fever in 2006. Kenya is hosting refugees from Somalia, Sudan, Rwanda, and the Congo.
WORDS TO KNOW
IMMIGRATION: The relocation of people to a different region or country for their native lands; also refers to the movement of organisms into an area in which they were previously absent.
IMPORTED CASE OF DISEASE: Imported cases of disease happen when an infected person who is not yet showing symptoms travels from his home country to another country and develops symptoms of his disease there.
INTERNATIONAL HEALTH REGULATIONS: International regulations introduced by the World Health Organization (WHO) that aim to control, monitor, prevent, protect against and respond to the spread of disease across national borders while avoiding unnecessary interference with international movement and trade.
ISOLATION: Isolation, within the health community, refers to the precautions that are taken in the hospital to prevent the spread of an infectious agent from an infected or colonized patient to susceptible persons. Isolation practices are designed to minimize the transmission of infection.
MIGRATION: In medicine, migration is the movement of a disease symptom from one part of the body to another, apparently without cause.
PREVALENCE: The actual number of cases of disease (or injury) that exist in a population.
STRAIN: A subclass or a specific genetic variation of an organism.
Impacts and Issues
Infectious diseases do not recognize borders. Accordingly, nations need to improve their medical surveillance to safeguard the health of their citizens. The IHR is one step in this direction. Screening and immunization programs would protect the health of immigrants and established residents. Canadian medical researchers have recommended that family doctors should ask young adult immigrants and refugees whether they have ever had chickenpox, test those who answer in the negative, and offer to vaccinate those who are susceptible to the disease.
Somalia until recently had an HIV prevalence rate of about one percent, which was lower than that of many African countries. After much cross-border movement of HIV-infected refugees from Ethiopia, the HIV infection rates in Somalia subsequently increased. By 2006, United Nations AIDS (UNAIDS) officials expressed fears that Somalia will experience a general AIDS epidemic within ten years. Condoms are generally unavailable in Somalia and there is a lack of adequate healthcare. Other African nations have experienced similar patterns of disease progression with HIV. Eleven African nations have HIV prevalence rates over 13%.
Political issues are also affecting international public health. Taiwan lacks full membership in WHO because of an historically strained relationship with mainland China. Taiwan has had more success than any other East Asian country in fighting H5N1, or avian influenza. Nevertheless, WHO has refused Taiwan's applications to attend avian flu-related international conferences, thus preventing Taiwan from effectively sharing its valuable experience in disease prevention. According to Taiwan's National Immigration Agency, an average of 1,200 people travel between Taiwan and China each day, and the number of Taiwanese traveling to the United States averages more than 1,600 per day.
In May 2007, a man with a strain of tuberculosis that is highly resistant to current drug therapies was the subject of the first federal order for isolation issued in the United States for over forty years after he re-entered the country from Canada. The man had traveled by air among several countries including France and Italy against the advice of his physicians who determined that he had tuberculosis. While abroad, medical personnel determined that his tuberculosis was the extremely resistant type (XDR-TB), and finally persuaded him to seek medical care, but only after he had returned to the United States. The CDC then began intensive efforts to track possible contacts that were in close contact with the infected man, including his fellow aircraft passengers and flight attendants.
The United Nations estimated that there were nearly 200 million international migrants in 2006—approximately 3% of the total global population. The annual number of migrants worldwide is likely increase. While immigration has the potential to spread disease, it also has brought attention to many health issues. Industrialized nations with large immigrant populations, such as the United States, have renewed interest in combating neglected diseases (diseases rare or eliminated in developed nations) across the globe. For example, international cooperative projects have sought to reduce incidence of tuberculosis and endemic parasitic diseases in Central and South America, as well as encourage screening and treatment for immigrants from those regions.
Primary Source Connection
The letter below to the editor of the journal Pediatrics highlights the special vaccination needs of children immigrating to the United States. Since Laurie C. Miller, a Boston-based physician specializing in internationally adopted children, wrote this letter in 1999, more than 100,000 additional children have been adopted by adults living in the United States. Miller is an associate professor of pediatrics and director of the International Adoption Clinic at Tufts University School of Medicine. She is the author of The Handbook of International Adoption Medicine: A Guide for Physicians, Parents, and Providers.
Internationally Adopted Children—Immigration Status
To the Editor,—
The number of internationally adopted children arriving in the United States has increased dramatically (13,620 in 1997, compared with 9,945 in 1986). Many children have received vaccines in their birth countries; however, the efficacy [effectiveness] of the vaccines and the accuracy of the records are sometimes questionable. Hostetter, et al. have reported protective diphtheria and tetanus titers in only 38 percent of Chinese, Russian, or Eastern European children with written evidence of age-appropriate vaccines.
We have observed that polio titers also may not be protective. Four children in our clinic with written evidence of 3 to 6 polio vaccines were found to have incompletely protective titers. The children were from Lithuania (1), Russia (2), and China (1). They ranged in age from 12 months to 8 years. In 3 children, protective titers to Type 1 and Type 2 polio were found, but no titers to Type 3 polio were measured. In one child, protective titers to Type 1 were absent, but were present for Types 2 and 3.
Although the Red Book recommends that “written documentation should be accepted as evidence of prior immunization,” clinicians caring for internationally adopted children should be aware of the possibility of incomplete immunity to polio, and should either revaccinate or verify immunity to all 3 types of polio. Revaccination or verification of protective titers should be considered for all immunizations in this population.
LAURIE C. MILLER, MD
International Adoption Clinic
New England Medical Center
Boston, MA 02111
Laurie C. Miller
MILLER,LAURIEC.“INTERNATIONALLY ADOPTED CHILDREN– IMMIGRATION STATUS.” LETTER TO THE EDITOR. PEDIATRICS. 103.5 (MAY 1999): P1078(1).
BIBLIOGRAPHY
Books
Clark, Robert P. Global Life Systems: Population, Food, and Disease in the Process of Globalization. Lanham, MD: Rowman and Littlefield, 2000.
Web Sites
World Health Organization. “International Health Regulations.” 2006 <http://www.who.int/csr/ihr/en/> (accessed May 17, 2007).
World Health Organization. “Tuberculosis and Air Travel: Guidelines for Prevention and Control.” 2006 <http://www.who.int/tb/publications/2006/who_htm_tb_2006_363.pdf> (accessed May 17, 2007).
Caryn E. Neumann