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Soil-Transmitted Helminths and Other Intestinal Roundworms

Abstract Infections with soil-transmitted helminths (STHs) affect the health of around 1.5 billion people around the world. Individuals of all ages may be infected with the common roundworm (Ascaris lumbricoides) , whipworm (Trichuris trichiura) , hookworm ( Ancylostoma duodenale and Necator americanus ), and Strongyloides stercoralis , although school-aged children living in resource-poor endemic areas are more likely to be infected with heavy worm burdens that…

Giardia, Cryptosporidium, Cyclospora, and Other Intestinal Protozoa

Abstract Giardia and Cryptosporidium are the two most common protozoan pathogens in the human intestine; in low-income countries, they also rank as leading causes of diarrhea in children under 5. Giardia duodenalis (previously G. lamblia or G. intestinalis ), was first discovered by Antoine van Leeuwenhoek, a 17th-century lens-grinder who invented the microscope, then found Giardia in his own stool. For the next several centuries, Giardia…

Amebiasis

Acknowledgments The authors would like to acknowledge the valuable contributions of the late Dr. Martin S. Wolfe to this chapter. Abstract Infection with Entamoeba histolytica is a leading parasitic cause of morbidity and mortality in developing nations and is an important health risk to travelers. Amebiasis is transmitted by parasite cysts via fecal-oral contamination from infected individuals or from contaminated food or water. Although most infected…

Primary Amebic Meningoencephalitis

Abstract Primary amebic meningoencephalitis (PAM) is an acute, progressive, and usually fatal condition caused by the free-living ameba Naegleria fowleri . Commonly referred to as the “brain-eating ameba,” N. fowleri is naturally found in warm freshwater (e.g., lakes, rivers, and hot springs), and soil. Infection with N. fowleri can occur when water containing the ameba enters the body through the nose. The ameba migrates to the…

Leptospirosis

Abstract Leptospirosis is the most common zoonosis worldwide and has recently emerged as an important travel-related infection, particularly in adventure travelers to the tropics and subtropics. Characteristic symptoms may include fever, headache, myalgias, jaundice, and conjunctival suffusion, but this disease often manifests as a nonspecific febrile illness. Because it has a wide range of signs and symptoms, a high index of suspicion is necessary for clinicians…

Lyme Disease

Abstract Lyme disease, caused by infection with spirochetes of the Borrelia burgdorferi complex, is the most common arthropod-borne infection in the United States. The spirochetes are transmitted to humans by bites of infected ticks of the Ixodes ricinus complex, which are also known as black-legged deer ticks. As many as 90% of patients have a characteristic rash, erythema migrans (EM); other manifestations of early disease include…

Tick-Borne Encephalitis

Acknowledgments I want to thank the companies of Baxter, Novartis, Pfizer, and GSK for providing information including data and graphics. In particular, Dr. Dieter Gniel was very helpful in sharing his vast experience on TBE. Abstract For a long time, tick-borne encephalitis (TBE) was perceived as a risk only (if ever) for the local populations living in endemic areas. There was very little specific awareness and…

West Nile Virus Disease

Abstract Before 1999, West Nile virus (WNV) received little attention outside Africa, Asia, and Europe, where it caused an endemic, mosquito-borne febrile illness and sporadic encephalitis. After the dramatic emergence of WNV in New York City in 1999, the virus spread westward across the United States, resulting in the largest outbreaks of WNV disease ever reported. From 1999 through 2018, 50,830 cases of WNV disease were…

Arboviruses of Medical Importance

Abstract Arboviruses are transmitted to humans primarily through the bites of arthropod vectors such as mosquitoes, ticks, and sandflies. Half of the world’s population live in areas endemic for arboviruses, which cause significant morbidity and mortality in both developed and developing countries. More than 130 arboviruses are known to infect humans, but only a much smaller number are medically important. Since 2015, there have been major…

Rabies

Acknowledgment The author acknowledges the work of Kis Robertson, Nina Marano, and Katherine J. Johnson on this chapter in the previous edition. Abstract Rabies has been recognized as a source of great human suffering and fear since ancient times. Characterized by a near 100% case fatality rate, it is among the deadliest infectious diseases known to humanity. The rabies virus (RABV) is present in the saliva…

Hepatitis A, B, C, D, and E: Focus on Adult Infections

Acknowledgment The authors acknowledge the work of Michael James Babineaux and Miriam J. Alter on this chapter in the previous edition. Abstract Viral hepatitis is caused by infection with five distinctly different human viruses that cannot be distinguished from one another without serologic testing ( Table 68.1 ). Hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis delta virus (HDV), and hepatitis…

Enteric Fever: Typhoid and Paratyphoid Fever

Abstract Infection with the gram-negative bacteria Salmonella enterica serotype Typhi ( S . Typhi) or S. enterica serotype Paratyphi A, B, or C ( S. Paratyphi A, B, or C) may result in a serious febrile illness known as enteric fever. The illness is called typhoid fever or paratyphoid fever once the causative agent has been identified. Pathogenic Salmonella bacteria causing invasive disease are a particular…

Cholera

Abstract Vibrio cholerae is a noninvasive small intestinal pathogen that produces cholera toxin, resulting in severe acute watery diarrhea in humans. Vibrio are gram-negative bacteria that live in marine and freshwater environments, and the O1 and O139 serogroups of V. cholerae can cause both endemic and epidemic cholera. Transmission occurs via the fecal-oral route, and humans lacking access to clean water are most likely to be…

Travelers’ Diarrhea

Abstract Acute diarrhea associated with travel is referred to as travelers’ diarrhea (TD) and is the most frequent illness among travelers. TD is defined as an acute illness associated with an increase in frequency and change in stool form (loose or liquid) compared with normal in an individual from one region who has traveled to another. It is frequently associated with other gastrointestinal symptoms that may…

Yellow Fever

Abstract Yellow fever (YF) is a vector-borne disease resulting from the transmission of the YF virus to a human from the bite of an infected mosquito. It is endemic to sub-Saharan Africa and tropical South America. Infection in humans can cause mild, undifferentiated febrile illness to severe disease with jaundice and hemorrhagic manifestations. All travelers to YF-endemic countries should be advised of the risks of acquiring…

Malaria

Abstract Malaria is a bloodborne protozoan parasite mostly transmitted from person to person by bites of infected female Anopheles mosquitoes in tropical and subtropical regions. Despite a substantial reduction in the malaria burden observed since 2010, largely attributed to effective control measures and treatment regimens, the World Health Organization (WHO) still reported 228 million infections and 405,000 deaths in 2018. The majority of deaths from malaria…

Introduction to Infections Associated With International Travel and Outdoor Activities

Abstract Travel in the broadest sense means going from one place to another, especially journeys to distant or unfamiliar places, and the theme of travel being associated with exposure to exotic infectious diseases (IDs) has been a recurring one throughout history. This section covers a variety of IDs that may be encountered during international travel and through participation in outdoor activities: these two kinds of exposures…

Bacterial Vaginosis, Related Syndromes, and Less Common Sexually Transmitted Diseases

Abstract Bacterial vaginosis (BV), the most common cause of vaginal discharge in the United States, is not traditionally described as a sexually transmitted infection (STI) but is well documented to be sexually associated. In the United States, two STIs—chancroid and granuloma inguinale—are uncommon diseases associated with genital ulcerations. These two infections may be encountered outside the United States and are significant risk factors for human immunodeficiency…

Syphilis (Treponema pallidum)

Abstract Syphilis is a complex systemic disease caused by the spirochete Treponema pallidum subspecies pallidum . Syphilis is transmitted sexually or congenitally and can involve nearly every organ system. Its clinical progression involves several well-characterized stages: (1) an incubation period of 1 week to 3 months; (2) a primary stage characterized by a chancre (an indurated, nontender ulcer at the site of exposure); (3) a secondary…