Infectious diseases and immigration

Definition: Communicable human diseases caused by pathogenic microorganisms

Significance:During North America’s colonial era, immigrants from Europe and Africa imported many contagious diseases that wreaked havoc on not only American Indian populations but also colonists. Successive waves of disease-carrying immigrants during the nineteenth century set off epidemics ranging from cholera to plague, despite ever more effective public health measures, and encountered effective anti-immigrant sentiment and action. During the early twenty-first century, visitors, as well as immigrants, posed threats to U.S. public health as carriers of new diseases and new strains of old diseases.

Every person and every community lives in an environment filled with bacteria, viruses, fungi, and parasites, many of which carry pathogens potentially lethal to humans. People who live for many years in the same area and with the same neighbors develop effective immune system defenses against commonly occurring pathogens. Sometimes they pass their immunity along to subsequent generations genetically. When a new pathogen is inserted into a community by changes in the environment or the intrusion of new people, the effects may be devastating, as existing members of the community may have limited or no developed biological defenses. Unlike noninfectious diseases such as diabetes or cancer, an infectious disease can be passed among members of a community by the actions of carriers of pathogens. These carriers might include tainted foods or water; insects, parasites, and their droppings; and infected people. During the centuries before germ theory made modern medicine an effective counter to most infectious diseases, there was little understanding of pathogens and carriers and little that any human community could do to defend against them.

Columbian Exchange

The early history of European and African settlement in the Western Hemisphere provides a depressingly long list of epidemics and pandemics. Many of these occurred on a large geographical scale, sparked by the contact of American Indian communities with immigrant men and women who carried deadly pathogens to which the carriers themselves were immune or highly resistant. American Indians died by the thousands from imported Old World diseases such as measles, mumps, smallpox, typhus, and influenza. This biological interaction is sometimes referred to as part of the “Columbian Exchange,” taking its name from the Italian explorer Christopher Columbus.

Although early immigrants from Europe and Africa tended to share resistance to a wide range of pathogens, later generations, long removed from their homelands and isolated from certain diseases in the New World, tended to lose their natural defenses to the Old World diseases. When new immigrants arrived from the Old World, even from the same cities and regions as the ancestors of second- or third-generation colonists or enslaved people, their reinfusion of disease-causing pathogens could and often did trigger outbreaks—even epidemics—among the settled immigrant populations. Perhaps ironically, however, this was least likely to occur in large cities such as New York, Boston, and Philadelphia, in which steady streams of new immigrants kept levels of exposure and resistance relatively high among the urban populations.

Some imported diseases, such as mosquito-borne malaria and yellow fever, were initially and inadvertently inserted into humid coastal environments in the New World that were well suited to the insects by Spanish slavers and their human cargoes. While the African immigrant populations were generally resistant to the potentially deadly diseases, both American Indians and Europeans proved to be highly susceptible. The insects became carriers when they sucked the blood of human carriers. In regions where human carriers diminished in number, as along the northern Atlantic coastline (thanks in part to the practice of quarantine), the incidence of the disease dropped off. Fresh arrivals of African or Caribbean enslaved people along the southern U.S. coasts, however, helped maintain high incidence levels. Even before Walter Reed and other researchers untangled the true nature of yellow fever during the early twentieth century, Americans sought strict limitations on immigrants and even trade from Cuba and other island sources of the disease whose carriers set off recurrent outbreaks.

Epidemics during the Age of Sail

Traditional Western medicine had long associated disease with filth, a lack of basic hygiene, and, by the later eighteenth century, poverty. From the 1820s, ships from Europe brought trickles and then floods of immigrants from Ireland and central Europe. Many of these people were both poverty-stricken and sick with opportunistic diseases such as typhus, influenza, and typhoid fever. Cramped and unsanitary quarters, lack of clean clothing, and poor nutrition shipboard exacerbated weak constitutions and undermined the healthy. Rightly fearful of the spread of infectious diseases, civic and state authorities in North America maintained quarantines and isolation facilities at major ports for sick or suspect passengers. Although a single case of influenza might be gotten over with no lasting effects, chronic conditions such as sexually transmitted diseases (STDs) and Hansen’s disease (leprosy) presented almost no possibility of cure. Those who suffered from such maladies would be turned away to find refuge elsewhere. They might then attempt to enter the country illicitly or simply return to their homelands.

Even due diligence could fail, especially with emerging diseases. Cholera had first broken out of its homeland in eastern India in 1817, but America was spared the ensuing first pandemic. The second pandemic proved less accommodating, and Irish immigrants brought the waterborne disease with them to Canadian and U.S. port cities in 1832. New York City lost 3,000 residents in July and August, and New Orleans suffered 4,340 fatalities during three weeks in October. Eventually spreading to the western frontier, cholera killed an estimated 150,000 people in North America between 1832 and 1849. The year 1866 saw the final epidemic of cholera in the United States when eastern and Gulf port cities counted 50,000 deaths.

The popular conception of Roman Catholic Irish immigrants as lazy, poor, and disease-ridden was reinforced by the huge numbers of penniless refugees who appeared as the potato famine (1845–52) ravaged their homeland. A British government report in 1856 noted that malnutrition and starvation among the Irish were accompanied by many other medical conditions, including infectious diseases: “fever, scurvy, diarrhea and dysentery, cholera, influenza, and ophthalmia.” Despite the availability of vaccines, smallpox “prevailed epidemically,” and typhus was nearly endemic in crowded Irish cities. Each year, hundreds of thousands of Irish died, and one-quarter million Irish emigrated. Although British port authorities were supposed to screen out emigrants carrying diseases before they departed, this task was often left to American officials. As a result, many emigrants died on ships, earning the passenger vessels the nickname “coffin ships.” Despite screening and quarantine procedures, many disease carriers still managed to enter the United States, and many of them settled in already overcrowded and unsanitary ethnic enclaves in American cities, inducing outbreaks as well as increased public health structures and efforts to combat the increasingly complex disease regimes.

Public Health and Anti-Immigrant Sentiment

The fact that a significant percentage of immigrants were Roman Catholic and, to a growing extent, Jewish, as well as poor and suffering from diseases, fed the fears and prejudices of nativists and other anti-immigrant groups. During the last decades of the nineteenth and first decades of the twentieth centuries, groups such as the Immigration Restriction League harnessed the ideas of new medical pseudosciences in their attempts to limit the diversity of immigrants. They blamed the perceived prevalence of certain diseases among eastern and central European immigrants, especially typhus and tuberculosis (TB), on natural genetic dispositions.

Tuberculosis was once widely considered to be a genteel or sensitive person’s disease. However, as it spread among the working classes in large U.S. cities, it became associated with poverty, squalor, and ethnic minorities, and sufferers were rounded up for isolation. A major outbreak in 1892 in New York City led to the passage of the National Quarantine Act of 1893. San Francisco’s bubonic plague outbreak in 1900–1901 was very likely sparked by stowaways aboard a visiting Japanese freighter. However, its first known fatality was a Chinese immigrant who lived in a very poor Chinese neighborhood. Residents of Chinatown, fearing both mobs and the government, hid subsequent cases of plague until the outbreak could no longer be concealed. Anti-Chinese sentiment then flashed across the city, and there were calls to eradicate the Asian American neighborhood. Cooler heads prevailed, however, and modern antiplague measures kept the number of fatalities to only 122.

The popular linkage of disease and immigrants remained a major factor in U.S. public policy. Along the U.S.-Mexican border, perfunctory visual inspections for obvious signs of diseases were replaced by mandatory flea-dip baths for large numbers of very poor laborers and immigrants who sought work or refuge from the dislocations of the Mexican Revolution after 1917. The worldwide influenza pandemic that followed World War I may have killed more than 40 million people, including 675,000 Americans—a fatality rate that was five times the annual average for that disease. Like the war itself, the pandemic underlined the metaphorical shrinkage of the world and the increasing immediacy of threats that included disease. This sentiment resulted in the federal immigration restriction acts of 1921 and 1924.

Modern Health Threats

Twentieth-century science and technology complicated ideas about the relationship between immigrants and infectious diseases. Medical researchers have found cures or effective treatments for a wide variety of potentially deadly diseases. While Americans generally have access to these, many are beyond the reach of potential immigrants. At the same time, jet aircraft have made intercontinental travel swift and relatively cheap. Visitors and U.S. travelers abroad, as well as immigrants, can and do enter America as carriers of a wide variety of pathogens.

Those who enter a country illicitly, or choose to remain undocumented, often avoid public health screening and surveillance officials who might identify them as carriers and treat their conditions. Instead, such individuals threaten members of the communities in which they settle. By the end of the twentieth century, tuberculosis was making an alarming resurgence across the globe, especially in developing countries in Asia and Africa. The United States has one of the world’s lowest levels of incidence of the disease, with only 3 cases per 100,000 population in 2014, but neighboring Mexico’s rate is far higher, with 21 cases per 100,000 population that year, according to World Bank data. TB presents a problem that is being echoed by other diseases: the natural evolution of drug-resistant varieties that threaten to make the American pharmaceutical arsenal obsolete.

Sexually transmitted diseases, including HIV/AIDS, can be treated, but immigrant communities are often resistant to public health measures. The worldwide spread of HIV/AIDS means that immigrants from Africa or Haiti are not alone suspect.

The incidences of forms of hepatitis, malaria, dengue fever, measles, and even leprosy were on the rise across the United States during the early twenty-first century, with health practitioners often noting the prevalence of foreign-born inhabitants or US visitors among their sufferers. The Ebola epidemic that spread across Guinea, Liberia, and Sierra Leone in 2013–14 prompted calls for a moratorium on travel visas being issued to those in affected countries, particularly after a Liberian visitor died of the disease in Texas and two nurses subsequently fell ill. The government ultimately did not enact a travel ban but forced travelers coming from West Africa—regardless of citizenship—to fly into one of five airports, undergo screening for symptoms, and submit to isolation, if necessary. Similarly, the Zika virus, linked with numerous congenital disabilities in Latin America in the mid-2010s, raised fears of an epidemic beginning in the United States through illegal immigration from Central America. In general, however, the rapidity of modern international travel outpaces disease symptom manifestation, making it difficult to manage disease transmission through border control, and analysts argue that the high prevalence of American travel overseas and the paradoxically better health of migrants makes it likelier that illnesses will be brought in by citizens returning home than by immigrants.

Since many modern-day immigrants find work in agricultural and food preparation and service sectors, the possibilities are good for spreading diseases beyond local communities. The failure to screen effectively those who cross America’s borders also opens the door for incidences of bioterrorism, as it raises the potential for other types of terrorism as well.

In the third decade of the twenty-first century, the COVID-19 pandemic affected nearly every aspect of American life, especially immigration. In April 2020, the Department of Homeland Security closed its borders with Canada and Mexico to all non-essential travel to slow the coronavirus spread during the pandemic. These restrictions were extended throughout the year. The spread of the coronavirus affected every aspect of American immigration—many remained trapped in immigrant detention centers, and the issuance of visas and temporary visas fell by over 50 percent. Further, immigrant workers were forced to continue employment at a higher rate during the pandemic and were disproportionately affected by the economic consequences of the COVID-19 pandemic.

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