East Asia

Risk of infection is highly variable in the region. Access to clean water and good sanitary facilities are limited in many rural areas, especially in China and Mongolia. Respiratory infections (etiology often undefined) are common in travelers to the region. Chronic and latent infections in immigrants (and long-term residents) include tuberculosis, complications from chronic hepatitis B (and also hepatitis C) infection, schistosomiasis, liver flukes, paragonimiasis (lung flukes), and strongyloidiasis.

Vector-borne infections: Malaria is found in focal areas of China and North and South Korea. Japanese encephalitis (JE) is found in wide areas of China and Japan and focally in Korea. Transmission of malaria and JE is seasonal in many areas. Reported infections in travelers are rare. Other vector-borne infections include dengue, which has caused outbreaks in mainland China, Hong Kong, and Taiwan; spotted fever caused by Rickettsia sibirica (China, Mongolia); murine typhus; Oriental spotted fever caused by R. japonica (Japan); rickettsialpox (Korea); scrub typhus (especially in China, Korea, and Japan); tick-borne encephalitis (in forested regions northeastern China and in South Korea); visceral and cutaneous leishmaniasis (in rural China); lymphatic filariasis (in focal coastal areas of China and South Korea); and Crimean-Congo hemorrhagic fever* (in western China).

Food- and water-borne infections: Risk of diarrhea is highly variable within the region. Diarrhea in travelers may be caused by bacteria, viruses, and parasites. Risk of hepatitis A is high in some areas (excluding Japan), especially in rural areas of China and Mongolia. Outbreaks of hepatitis E have been reported in China. Cases of cholera were reported from China in 2004; most of the cases reported from Japan in 2004 were imported (55 of 66). Sporadic cases of anisakiasis are reported from Korea and Japan. Brucellosis is found, especially in sheep-raising regions of China and Mongolia (annual incidence >500 per 100,000 population in Mongolia) (16). Paragonimiasis is endemic in China (an estimated 20 million are infected) and still occurs in Korea. Liver flukes (causing clonorchiasis and fascioliasis) are endemic in the region (in 2004 the infected population in China was estimated to be 15 million), but risk to usual traveler is low.

Airborne and person-to-person transmission: The estimated annual incidence of tuberculosis per 100,000 population is 100-300 in China, Mongolia, and North Korea; 25-50 in Japan; and 50-100 in South Korea. High rates of multidrug-resistant tuberculosis are found in parts of China (3%-6% overall in new cases and as high as 10% in some areas). Outbreaks of SARS occurred in mainland China, Hong Kong, and Taiwan in 2003. Measles remains endemic in the region, and infection has occurred in adopted children from China and in travelers to the region. In tropical areas, influenza may occur during all months of the year.

Sexually transmitted and blood-borne infections: The prevalence of HIV in adults is low (0.1%-<0.5%) in most of the region, but a much higher prevalence is found in focal areas in southern China. Hepatitis B is highly endemic among adults in the region, excluding Japan. Prevalence of chronic infection exceeds 8% in many areas. Prevalence of hepatitis C is 10% or higher in Mongolia; 2.0%-2.9% in mainland China and Taiwan, and slightly lower in the rest of the region. A high prevalence of HTLV-I is found focally in the southern islands of Japan.

Zoonotic infections: Rabies is widespread in China (not Hong Kong) and Mongolia. In 2005, a reported 2545 people died from rabies in China; outbreaks in 2006 have led to mass killings of dogs. Rates of rabies vaccine coverage in pet dogs have been low. Highly pathogenic avian influenza (H5N1) continues to cause outbreaks in domestic and wild bird populations and has caused human cases and deaths in Hong Kong and China. Highly pathogenic H5N1 was also found in bird populations in Japan and South Korea in 2003-2004. Cases of human plague* are reported most years from China and Mongolia. Hantaviruses causing hemorrhagic fever with renal syndrome are a major health threat in China and the Republic of Korea, primarily affecting residents of rural areas in late fall and early winter. Risk to the usual traveler is low. Anthrax* is enzootic in China and Mongolia, and sporadic infection is reported in the rest of the region. Tularemia* occurs in China and Japan and is found especially in northern parts of region. Echinococcosis* is endemic in rural areas of China and Mongolia.

In 2005 a large outbreak of human Streptococcus suis infection caused 215 cases (66 laboratory confirmed) (18) in Sichuan, China. Infection occurred in farmers ex-posed to backyard pigs during slaughter.

Soil- and water-associated infections: Schistosomiasis (Schistosoma japonicum) is present in focal areas in China, especially in the Yangtze River basin. An estimated 60 million people live in at-risk areas. Leptospirosis* is a risk, especially in tropical areas of China and South Korea. Cutaneous larva migrans is common in warm coastal areas. Cases of histoplasmosis have been reported.

Other hazards: Injury from motor vehicle accidents and venomous snake bites occur. Screening of blood before transfusion is inadequate in many hospitals in the region.

List of Countries

Southeast Asia

More common infections in travelers to the area include dengue fever, respiratory infections, and diarrheal infections. Chronic and latent infections in immigrants (and long-term residents) include tuberculosis, late complications of hepatitis B infection, intestinal helminth infections (including strongyloidiasis), and other helminth infections, such as paragonimiasis, opisthorchiasis, and clonorchiasis.

Vector-borne infections: Dengue fever is hyperendemic in the region, and epidemics are common; cases occur in travelers to the region. Malaria is found in focal areas (primarily rural) in all these countries (except Brunei and Singapore), especially in rural areas. Japanese encephalitis is widely distributed in the region and is hyperendemic in some areas; risk is seasonal in some countries. Scrub typhus is a common cause of fever in the region. Other vector-borne infections include murine typhus, chikungunya virus, and relapsing fever. Foci of transmission of lymphatic filariasis are found throughout the area, with the exception of some of the Indonesian islands.

Food- and water-borne infections: Risk of hepatitis A is widespread in the region. Risk of diarrhea caused by bacteria, viruses, and parasites is high in parts of the area. An outbreak of polio (more than 300 virus-confirmed cases) occurred in Indonesia in 2005 after importation of the virus from Nigeria. Campylobacter infections are especially common in Thailand and are often resistant to fluoroquinolones. Amebic liver abscesses, typhoid fever, and brucellosis occur. Isolates of Salmonella causing typhoid fever may be resistant to multiple drugs, including the fluoroquinolones. Cholera epidemics have been common in the past; cases were reported from Cambodia, Malaysia, and the Philippines in 2004. Outbreaks of hepatitis E have been reported from the region (Indonesia and Burma). Cysticercosis is especially common in Indonesia. Gnathostomiasis is endemic in region and especially common in Thailand. Intestinal helminth infections are common in some rural areas; risk to the usual traveler is low. Opisthorchiasis, clonorchiasis, fasciolopsiasis, and paragonimiasis are endemic in parts of the region (especially Laos and Burma).

Airborne and person-to-person transmission: The annual incidence rate of tuberculosis per 100,000 population is estimated to be more than 300 in Cambodia and 100-300 in the rest of the region. Measles transmission persists in the region, although vaccination coverage is improving in some countries. SARS outbreaks occurred in the region (especially in Singapore and Vietnam) in 2003. Influenza infections can occur throughout the year in tropical areas.

Sexually transmitted and blood-borne infections: The prevalence of HIV in adults is 1%-<5% in Thailand, Burma (Myanmar), and Cambodia and <1% in the rest of the region. Higher prevalences may be found in specific populations. The prevalence of hepatitis B chronic carriage exceeds 8% in many parts of region. The prevalence of chronic hepatitis C is 1%-2.4%. Chancroid is a common cause of genital ulcer disease.

Zoonotic infections: Rabies is common in the region, and travelers are at risk for exposure to rabid animals, especially dogs. Highly pathogenic avian influenza (H5N1) has been found in poultry populations in most countries of the region. Human cases and deaths have been reported in Thailand, Vietnam, Indonesia, and Cambodia. In 2006, the virus continued to spread in poultry populations in Indonesia. Anthrax* is hyperendemic in Burma; sporadic cases occur in much of the rest of the region. An outbreak of Nipah virus, with a probable reservoir in fruit bats and documented transmission to humans from pigs, occurred in Malaysia (1998-1999) and in Singapore (after contact with pigs imported from Malaysia). Cases of human plague* have been reported since 1990 from Indonesia, Laos, Burma, and Vietnam.

Soil- and water-associated infections: Schistosomiasis caused by S. japonicum is found in the Philippines and Indonesia (Sulawesi [Celebes]); caused by S. mekongi in Cambodia and Laos; and caused by S. malayensis in peninsular Malaysia. Leptospirosis* is common in tropical areas and has been reported in travelers to the area. Melioidosis is a common cause of community-acquired sepsis, especially in rural areas of Thailand; it is also common in Cambodia, Laos, and Vietnam. Cases have in-creased in 2004 in Singapore. Infection in travelers is rare. Penicilliosis marneffei is found in Southeast Asia and is a common opportunistic infection in HIV-infected patients, especially in Thailand. Rare cases have been reported in travelers to the region. Cutaneous larva migrans is common on warm coastal areas.

Other hazards: Snake bites and motor vehicle accidents occur. Screening of blood before transfusion is inadequate in many hospitals.

South Asia

More common infections in travelers are gastrointestinal infections (including acute bacterial diarrhea and amebic disease), typhoid fever, and malaria. Chronic and latent infections in immigrants (or long-term residents) include tuberculosis, cysticercosis, visceral leishmaniasis, lymphatic filariasis, echinococcosis, and intestinal helminths. Primary varicella may be seen in adults, as childhood infection is less common in tropical areas.

Vector-borne infections: Malaria is widespread in areas at altitudes lower than 2000 meters and is found in the Terai and Hill districts of Nepal at altitudes lower than 1200 meters. Dengue fever has caused epidemics in all these countries except Nepal. Japanese encephalitis transmission occurs widely in lowland areas of the region (except for Afghanistan). Severe outbreaks occurred in India in 2005. Transmission is seasonal. Focal areas of transmission of visceral leishmaniasis are present in rural India, Pakistan, Nepal, and Bangladesh. Major epidemics of visceral leishmaniasis have occurred in eastern India (especially Assam and Bihar states). Cutaneous leishmaniasis is present in Afghanistan, (where it has infected US troops); India; and Pakistan. Lymphatic filariasis is endemic in large areas of India, Sri Lanka, and Bangladesh. Other vector-borne infections include scrub typhus, murine typhus, epidemic typhus (in remote, cooler areas), relapsing fever, sandfly fever, spotted fever due to R. conorii (especially in India), Kyasanur Forest disease (tick-borne; Karnataka State, India, and Pakistan), and Crimean-Congo hemorrhagic fever* (in Pakistan and Afghanistan). In 2005-2006, an outbreak of chikungunya affected thousands of persons in India.

Food- and water-borne infections: Hepatitis A is widespread, and risk to travelers is high. Large outbreaks of hepatitis E have occurred in Bangladesh, India, Nepal, and Pakistan. Typhoid and paratyphoid fever (increasingly resistant to multiple antimicrobial agents) occur sporadically and in outbreaks and can affect travelers to the region. Amebic infections are common and can cause liver abscesses. Indigenous wild polio was present in in 2005-2006 in India, Pakistan, and Afghanistan; cases from Bangladesh and Nepal were confirmed in 2005-2006. Cyclospora infections have been reported, especially from Nepal. Cholera outbreaks have occurred frequently in the region, especially in Bangladesh and India. Cysticercosis is found, especially in India. Paragonimiasis is endemic in India (Manipur province). Gnathostomiasis has caused sporadic cases and outbreaks.

Airborne and person-to-person: The annual incidence rates of tuberculosis per 100,000 population are estimated to be higher than 300 in Afghanistan and 100-300 in most of the rest of the region. Measles occurs in the region and can be a source of infection for unvaccinated travelers.

Sexually transmitted and blood-borne infections: The prevalence of HIV in adults is less than 1% in most of the region but is rising rapidly in some populations in India (seroprevalence higher than 5% in some antenatal clinics). The prevalence of chronic infection with hepatitis B is 2%-7% in most of the region.

Zoonotic infections: Rabies is common in the region and poses a risk to travelers. Q fever* is widespread. Anthrax* is endemic in much of the region, and cases occur sporadically. Plague* is endemic in India, and outbreaks have occurred. Echinococcosis* is highly endemic in focal rural areas. An outbreak of Nipah virus (encephalitis) occurred in Bangladesh in early 2004, and person-to-person spread may have occurred. Macaques throughout the region are infected with B virus (Herpes).

Highly pathogenic avian influenza (H5N1) has been found in poultry populations in India and Pakistan.

Soil- and water-associated infections: Leptospirosis* is common, especially in tropical areas.

Other hazards: There may be a risk for snake bites, injury from motor vehicle accidents, and injury related to ongoing conflicts. Screening of blood before transfusion is inadequate in many hospitals.

MAP 3-04 Regions - Asia