Travelers' diarrhea is the most common travel-related ailment. The cornerstone of prevention is food and water precautions, as outlined below. All travelers should bring along an antibiotic and an antidiarrheal drug to be started promptly if significant diarrhea occurs, defined as three or more loose stools in an 8-hour period or five or more loose stools in a 24-hour period, especially if associated with nausea, vomiting, cramps, fever or blood in the stool. A quinolone antibiotic is usually prescribed: either ciprofloxacin (Cipro)(PDF) 500 mg twice daily or levofloxacin (Levaquin) (PDF) 500 mg once daily for a total of three days. Quinolones are generally well-tolerated, but occasionally cause sun sensitivity and should not be given to children, pregnant women, or anyone with a history of quinolone allergy. Alternative regimens include a three day course of rifaximin (Xifaxan) 200 mg three times daily or azithromycin (Zithromax) 500 mg once daily. Rifaximin should not be used by those with fever or bloody stools and is not approved for pregnant women or those under age 12. Azithromycin should be avoided in those allergic to erythromycin or related antibiotics. An antidiarrheal drug such as loperamide (Imodium) or diphenoxylate (Lomotil) should be taken as needed to slow the frequency of stools, but not enough to stop the bowel movements completely. Diphenoxylate (Lomotil) and loperamide (Imodium) should not be given to children under age two.

Most cases of travelers' diarrhea are mild and do not require either antibiotics or antidiarrheal drugs. Adequate fluid intake is essential.

If diarrhea is severe or bloody, or if fever occurs with shaking chills, or if abdominal pain becomes marked, or if diarrhea persists for more than 72 hours, medical attention should be sought.

Though effective, antibiotics are not recommended prophylactically (i.e. to prevent diarrhea before it occurs) because of the risk of adverse effects, though this approach may be warranted in special situations, such as immunocompromised travelers.

Malaria in Hong Kong: extremely limited risk in rural areas. Prophylaxis is not recommended. There is no risk in urban areas.

The following are the recommended vaccinations for Hong Kong:

Influenza vaccine is recommended for all travelers (see "Recent outbreaks" below). The vaccine may cause soreness at the injection site, low-grade fevers, malaise, and muscle aches. Severe reactions are rare. Influenza vaccine should not be given to pregnant women during the first trimester.

Hepatitis A vaccine is recommended for all travelers over one year of age. It should be given at least two weeks (preferably four weeks or more) before departure. A booster should be given 6-12 months later to confer long-term immunity. Two vaccines are currently available in the United States: VAQTA (Merck and Co., Inc.) (PDF) and Havrix (GlaxoSmithKline) (PDF). Both are well-tolerated. Side-effects, which are generally mild, may include soreness at the injection site, headache, and malaise.

Older adults, immunocompromised persons, and those with chronic liver disease or other chronic medical conditions who have less than two weeks before departure should receive a single intramuscular dose of immune globulin (0.02 mL/kg) at a separate anatomic injection site in addition to the initial dose of vaccine. Travelers who are less than one year of age or allergic to a vaccine component should receive a single intramuscular dose of immune globulin (see hepatitis A for dosage) in the place of vaccine.

Tetanus-diphtheria vaccine is recommended for all travelers who have not received a tetanus-diphtheria immunization within the last 10 years.

Measles-mumps-rubella vaccine: two doses are recommended (if not previously given) for all travelers born after 1956, unless blood tests show immunity. Many adults born after 1956 and before 1970 received only one vaccination against measles, mumps, and rubella as children and should be given a second dose before travel. MMR vaccine should not be given to pregnant or severely immunocompromised individuals.

An isolated human case of H5N1 avian influenza ("bird flu") was reported from Hong Kong in November 2010. Poultry outbreaks of H5N1 influenza have occurred periodically over the last several years. A single case was identified at a poultry market in Hong Kong in December 2011, leading to the culling of thousands of chickens. An outbreak was reported from a chicken farm in December 2010. Poultry outbreaks were previously reported in June 2008, December 2008, and March 2010. Most travelers are at extremely low risk for avian influenza, since almost all human cases have occurred in those who have had direct contact with live, infected poultry, or sustained, intimate contact with family members suffering from the disease. The World Health Organization and the Centers for Disease Control do not advise against travel to countries affected by avian influenza, but recommend that travelers should avoid exposure to live poultry, including visits to poultry farms and open markets with live birds; should not touch any surfaces that might be contaminated with feces from poultry or other animals; and should make sure all poultry and egg products are thoroughly cooked. A vaccine for avian influenza was recently approved by the U.S. Food and Drug Administration (FDA), but produces adequate antibody levels in fewer than half of recipients and is not commercially available. The vaccines for human influenza do not protect against avian influenza. Anyone who develops fever and flu-like symptoms after travel to Hong Kong should seek immediate medical attention, which may include testing for avian influenza. For further information, go to the World Health Organization, Health Canada, the Centers for Disease Control, and ProMED-mail.

An outbreak of paralytic shellfish poisoning was reported from Hong Kong in May 2010, related to ingestion of fresh scallops. The Centre for Health Protection has advised people not to eat fresh scallops until further notice (see ProMED-mail).

A small outbreak of hand, foot and mouth disease caused by enterovirus 71 was reported from Hong Kong in April 2008, at the same time that a much larger outbreak was occurring in mainland China. As of July 2008, a total of 100 cases of hand, foot and mouth disease had been identified, of which 66 were caused by enterovirus 71. Three cases of enterovirus 71 infection were reported in March 2009, all from the same nursery school. Cases of enterovirus 71 infections have been reported annually from Hong Kong since August 1998, when the first outbreak occurred. Hand, foot, and mouth disease is characterized by fever, oral blisters, and a rash or blisters on the palms and soles, usually occurring in young children. Most cases resolve uneventfully, but a small percentage are complicated by encephalitis (inflammation of the brain), myocarditis (inflammation of the heart muscle), or pulmonary edema (fluid in the lungs). The disease is caused by enteroviruses, which are transmitted by exposure to fecal material from infected individuals. There is no vaccine. The key to prevention is good personal hygiene and scrupulous hand-washing, especially after defecation and before handling food. No travel restrictions are recommended.

An increase in the number of hepatitis E infections was reported for the first quarter of 2008. Hepatitis E virus is transmitted by contaminated food or water. The mortality rate is particularly high in pregnant women. There is no vaccine. To prevent hepatitis E, food and water precautions should be strictly followed, as below.

An influenza outbreak in March 2008 led to the closing of all primary schools and kindergartens for two weeks (see ProMED-mail; March 15,2008). Influenza vaccine is recommended for all travelers to Hong Kong during influenza season (November through April).

Three cases of Japanese encephalitis were reported from the New Territories in June-July 2004, followed by a fourth case in October. An isolated case was reported in July 2011, the first in four years. Japanese encephalitis is a life-threatening viral infection transmitted by mosquitoes, usually in rural areas where rice paddies and pig farming co-exist. For most travelers, the risk of Japanese encephalitis is extremely low. Japanese encephalitis vaccine, which requires a total of three injections over one month, is recommended only for those who expect to be staying in rural areas in the New Territories for more than one month or who expect to engage there in extensive unprotected outdoor activities, especially in the evening. Insect protection measures, as described below, are strongly advised for all travelers to the New Territories. For further information, go to ProMED-mail and the Centers for Disease Control.

Three cases of leptospirosis were reported in September 2004 among participants in the hiking activity "Team Challenge 36" held in August 2004. All those infected had uncovered wounds or abrasions which had been soaked with water during activities such as rafting. Sporadic cases have been reported from Hong Kong since that time. Leptospirosis is transmitted to humans by exposure to water contaminated by the urine of infected animals. Symptoms may include fever, chills, headache, muscle aches, joint pains, and conjunctivitis. Travelers who participate in activities which place them at risk for leptospirosis should take doxycycline 200 mg once weekly as prophylaxis.

An outbreak of severe acute respiratory syndrome (SARS) was reported in March 2003, resulting in 1755 cases and 296 deaths. The outbreak was terminated by an aggressive program of contact identification and quarantine. The disease is caused by a previously unknown virus belonging to the coronavirus family. The incubation period usually ranges from two-to-seven days, but may be as long as ten days. The first symptom is usually fever, often accompanied by chills, headache, body aches, and malaise. This is typically followed by dry cough and difficulty breathing, at times severe enough to require intubation and mechanical ventilation.

The outbreak in Hong Kong appeared to have been triggered by a visitor from mainland China who was ill with pneumonia while staying at the Metropole hotel in Kowloon (Hong Kong) from February 15 to 23. Seven people who stayed in or visited the same floor of the hotel at that time, including a Chinese-American businessman who flew on to Hanoi, one Hong Kong resident, three visitors from Singapore and two visitors from Canada, went on to develop SARS and start outbreaks in their countries.

Almost all the initial cases occurred in health care workers or in family members or other close contacts of those with the disease. However, as the outbreak developed, more than 300 cases were identified among residents of a large housing estate called Amoy Garden, probably caused by contamination of the sewage system by infected fecal material from a man who had SARS and diarrhea. For further information, go to the World Health Organization, the Hong Kong Department of Health, Health Canada, and the Centers for Disease Control.

An outbreak of H5N1 avian influenza("bird flu"), resulting in 18 human cases and six deaths, was reported in 1997. All cases were acquired through direct exposure to live, infected poultry. There was no evidence of person-to-person spread. The outbreak was terminated by mass slaughter of poultry. For further information, go to the World Health Organization, ProMED-mail, and the Office international des epizooties.In February 2003, two residents of Hong Kong developed avian influenza while visiting relatives in Fujian province in southern China. One of the cases was fatal. See the World Health Organization for further information.

A small number of cases of influenza caused by a strain similar to quail viruses (H9N2) were reported from Hong Kong in 1999. There were no fatalities. Cases of H9N2 influenza were also reported in a 5-year-old boy in December 2003 and a 9-month-old girl in March 2007. Both recovered uneventfully.

Transmission of dengue fever, a viral infection which is widespread in Asia but not previously occurring in Hong Kong, was reported for the first time in September 2002. As of October 9, a total of 20 locally acquired cases had been identified. Dengue fever is a flu-like illness which is sometimes complicated by hemorrhage or shock. The disease is transmitted by Aedes mosquitoes, which bite primarily in the daytime and favor densely populated areas, though they also inhabit rural environments. At present, the risk to travelers to Hong Kong appears low. For further information, go to ProMED-mail (October 7, 2002).

A single case of variant Creutzfeldt-Jakob disease (CJD) has been reported in Hong Kong, but the victim is believed to have acquired the disease while living in the United Kingdom. The disease is acquired by eating beef from cows with a related infection known as bovine spongiform encephalopathy (mad cow disease). There has been no evidence of mad cow disease in Hong Kong.

Gnathostomiasis, which is caused by a helminth known as Gnathostoma spinigerum, may be acquired by eating raw or undercooked freshwater fish. The chief symptom is intermittent, migratory swellings under the skin, sometimes associated with joint pains, muscle pains, or gastrointestinal symptoms. The symptoms may not begin until many months after exposure. See Moore et al. in Emerging Infectious Diseases for further information.

Streptococcus suis infections occur sporadically in Hong Kong. A total of six cases were identified in the year 2008, six cases in 2009, and ten cases in 2010. Most human cases occur in adult male farmers or butchers who have had direct contact with diseased or dead pigs. Symptoms included high fever, malaise, nausea, and vomiting, followed in severe cases by meningitis, subcutaneous hemorrhage, toxic shock, and coma. There is no evidence of person-to-person transmission. Travelers are at low risk.

HIV (human immunodeficiency virus) infection is reported, but travelers are not at risk unless they have unprotected sexual contacts or receive injections or blood transfusions.

For up-to-date statistics on many infectious diseases, including influenza, go to the Hong Kong Department of Health website. For an overview of health care in Hong Kong, go to the World Health Organization - Western Pacific Region.

Do not eat fruits or vegetables unless they have been peeled or cooked. Avoid cooked foods that are no longer piping hot. Cooked foods that have been left at room temperature are particularly hazardous. Avoid unpasteurized milk and any products that might have been made from unpasteurized milk, such as ice cream. Avoid food and beverages obtained from street vendors. Do not eat raw or undercooked meat or fish. Some types of fish may contain poisonous biotoxins even when cooked, including red snapper, grouper, amberjack, sea bass, and a large number of tropical reef fish.

All travelers should bring along an antibiotic and an antidiarrheal drug to be started promptly if significant diarrhea occurs, defined as three or more loose stools in an 8-hour period or five or more loose stools in a 24-hour period, especially if accompanied by nausea, vomiting, cramps, fever or blood in the stool. Antibiotics which have been shown to be effective include ciprofloxacin (Cipro), levofloxacin (Levaquin), rifaximin (Xifaxan), or azithromycin (Zithromax). Either loperamide (Imodium) or diphenoxylate (Lomotil) should be taken in addition to the antibiotic to reduce diarrhea and prevent dehydration.

If diarrhea is severe or bloody, or if fever occurs with shaking chills, or if abdominal pain becomes marked, or if diarrhea persists for more than 72 hours, medical attention should be sought.

Wear long sleeves, long pants, hats and shoes (rather than sandals). Apply insect repellents containing 25-50% DEET (N,N-diethyl-3-methylbenzamide) or 20% picaridin (Bayrepel) to exposed skin (but not to the eyes, mouth, or open wounds). DEET may also be applied to clothing. Products with a lower concentration of either repellent need to be repplied more frequently. Products with a higher concentration of DEET carry an increased risk of neurologic toxicity, especially in children, without any additional benefit. Do not use either DEET or picaridin on children less than two years of age. For additional protection, apply permethrin-containing compounds to clothing, shoes, and bed nets. Permethrin-treated clothing appears to have little toxicity. Don't sleep with the window open unless there is a screen. If sleeping outdoors or in an accomodation that allows entry of mosquitoes, use a bed net, preferably impregnated with insect repellent, with edges tucked in under the mattress. The mesh size should be less than 1.5 mm. If the sleeping area is not otherwise protected, use a mosquito coil, which fills the room with insecticide through the night.

Bring adequate supplies of all medications in their original containers, clearly labeled. Carry a signed, dated letter from the primary physician describing all medical conditions and listing all medications, including generic names. If carrying syringes or needles, be sure to carry a physician's letter documenting their medical necessity.Pack all medications in hand luggage. Carry a duplicate supply in the checked luggage. If you wear glasses or contacts, bring an extra pair. If you have significant allergies or chronic medical problems, wear a medical alert bracelet.

Make sure your health insurance covers you for medical expenses abroad. If not, supplemental insurance for overseas coverage, including possible evacuation, should be seriously considered. If illness occurs while abroad, medical expenses including evacuation may run to tens of thousands of dollars. For a list of travel insurance and air ambulance companies, go to Medical Information for Americans Traveling Abroad on the U.S. State Department website. Bring your insurance card, claim forms, and any other relevant insurance documents. Before departure, determine whether your insurance plan will make payments directly to providers or reimburse you later for overseas health expenditures. The Medicare and Medicaid programs do not pay for medical services outside the United States.

Pack a personal medical kit, customized for your trip (see description). Take appropriate measures to prevent motion sickness and jet lag, discussed elsewhere. On long flights, be sure to walk around the cabin, contract your leg muscles periodically, and drink plenty of fluids to prevent blood clots in the legs. For those at high risk for blood clots, consider wearing compression stockings.

Avoid contact with stray dogs and other animals. If an animal bites or scratches you, clean the wound with large amounts of soap and water and contact local health authorities immediately. Wear sun block regularly when needed. Use condoms for all sexual encounters. Ride only in motor vehicles with seat belts. Do not ride on motorcycles.

For an ambulance in Hong Kong, call 999. Response times are generally good.

High quality medical care is widely available. Many physicians are Western-trained. Many expatriates go to the Hong Kong Adventist Hospital (40 Stubbs Road, Hong Kong; tel. 852-2574-6211; website http://www.hkah.org.hk/en/index.html; member of the international networks of the Massachusetts General Hospital and the New York-Presbyterian Hospital, two leading U.S. hospitals), which offers 24-hour urgent care as well as international travel medicine services. In the New Territories, the leading facility is Tsuen Wan Adventist Hospital (199 Tsuen King Circuit, Tsuen Wan, N.T.; tel. 852 2276-7676; website http://www.twah.org.hk/en/index.html). Both of these hospitals have been accredited by the Joint Commission International.

Specialty care in infectious and tropical diseases is provided by Dr. John Simon, who trained at leading institutions in the UK (Central Medical Practice, 1501 Prince's Building, Central Hong Kong; ph. 852-252-12567; email john-dr.simon@hkg.dupont.com). Twenty-four hour medical care for uncomplicated problems is available at TY Medical Practice (see their website at http://www.tyhealthcare.com/ for locations). For a guide to other physicians, dentists, and hospitals, go to the U.S. Embassy website. For a more complete listing of physicians and dentists in Hong Kong, go to the Hong Kong Medical Union. Many medical facilities will expect payment in cash.

Most pharmacies are well-supplied. Prescription drugs are widely available, although they may have different names than those in North America or Europe. Many travelers go to the Family Centre Pharmacy Ltd (G/F, 74 Hennessy Road, Wanchai, Hong Kong; ph. 2527-4751, 2527-5748; hours: Mon - Sat 9 AM – 7 PM, closed on Sundays; open holidays 10 AM – 5 PM; payment by cash or check).

Before you leave, make sure you have the names and contact information for physicians, clinics, and hospitals where you can obtain emergency medical care if needed (see the U.S. Embassy website).

All children should be up-to-date on routine childhood immunizations, as recommended by the American Academy of Pediatrics. Children who are 12 months or older should receive a total of 2 doses of MMR (measles-mumps-rubella) vaccine, separated by at least 28 days, before international travel. Children between the ages of 6 and 11 months should be given a single dose of measles vaccine. MMR vaccine may be given if measles vaccine is not available, though immunization against mumps and rubella is not necessary before age one unless visiting a country where an outbreak is in progress. Children less than one year of age may also need to receive other immunizations ahead of schedule (see the accelerated immunization schedule).

When traveling with young children, be particularly careful about what you allow them to eat and drink (see food and water precautions), because diarrhea can be especially dangerous in this age group and because the vaccines for hepatitis A and typhoid fever, which are transmitted by contaminated food and water, are not approved for children under age two. Baby foods and cows' milk may not be available in developing nations. Only commercially bottled milk with a printed expiration date should be used. Young children should be kept well-hydrated and protected from the sun at all times.

Be sure to pack a medical kit when traveling with children. In addition to the items listed for adults, bring along plenty of disposable diapers, cream for diaper rash, oral replacement salts, and appropriate antibiotics for common childhood infections, such as middle ear infections.

International travel should be avoided by pregnant women with underlying medical conditions, such as diabetes or high blood pressure, or a history of complications during previous pregnancies, such as miscarriage or premature labor. For pregnant women in good health, the second trimester (18–24 weeks) is probably the safest time to go abroad and the third trimester the least safe, since it's far better not to have to deliver in a foreign country.

Before departure, make sure you have the names and contact information for physicians, clinics, and hospitals where you can obtain emergency obstetric care if necessary (see the U.S. Embassy website). In general, pregnant women should avoid traveling to countries which do not have modern facilities for the management of premature labor and other complications of pregnancy.

Strict attention to food and water precautions is especially important for the pregnant traveler because some infections, such as listeriosis, have grave consequences for the developing fetus. Additionally, many of the medications used to treat travelers' diarrhea may not be given during pregnancy. Quinolone antibiotics, such as ciprofloxacin (Cipro) and levofloxacin (Levaquin), should not be given because of concern they might interfere with fetal joint development. Data are limited concerning trimethoprim-sulfamethoxazole, but the drug should probably be avoided during pregnancy, especially the first trimester. Options for treating travelers' diarrhea in pregnant women include azithromycin and third-generation cephalosporins. For symptomatic relief, the combination of kaolin and pectin (Kaopectate; Donnagel) appears to be safe, but loperamide (Imodium) should be used only when necessary. Adequate fluid intake is essential.

Helpful maps are available in the University of Texas Perry-Castaneda Map Collection and the United Nations map library. If you have the name of the town or city you'll be visiting and need to know which state or province it's in, you might find your answer in the Getty Thesaurus of Geographic Names.

U.S. citizens living or traveling in Hong Kong are encouraged to register with the nearest U.S. Embassy or Consulate through the State Department's travel registration website, https://travelregistration.state.gov, and to obtain updated information on travel and security within Hong Kong. U.S. citizens without Internet access may register directly with the nearest U.S. Embassy or Consulate. By registering, U.S. citizens make it easier for the Embassy or Consulate to contact them in case of emergency. The U.S. Consulate General is located at 26 Garden Road, Central, Hong Kong. The U.S. mailing address is PSC 461, Box 5, FPO AP 96521-0006, tel. (852) 2523-9011, fax (852) 2845-4845; Web site: http://hongkong.usconsulate.gov; email address: acshnk@yahoo.com. The American Citizens Services Unit (ACS) is open to the public from 8:30 am to 12 noon and 1:30 pm to 4:00 pm, Monday through Friday except Wednesday afternoons and U.S. and local holidays.

For information on safety and security, go to the U.S. Department of State, United Kingdom Foreign and Commonwealth Office, Foreign Affairs Canada, and the Australian Department of Foreign Affairs and Trade.