Foodborne Infections

Ingestion of contaminated food or water makes travel-associated diarrhea the most common health complaint among international travelers. Among the bacterial and protozoan infections that children can acquire from contaminated water are shigellosis, salmonellosis, Escherichia coli infections, cholera, giardiasis, amebiasis, and cryptosporidiosis. Viral infections, particularly rotavirus infections, are also a major cause of travel-associated diarrhea in children. Boiled water, hot beverages made with boiled water, and canned or bottled carbonated beverages are generally safest. Ice should be avoided, and tap water should not be used when brushing teeth. Boiling water for ≥1 min (or 3 min at altitudes >2000 m) is the most reliable method of disinfecting water. An acceptable alternative is the use of a micropore filter with an on-demand iodine-release system. Unpeeled fruit, uncooked vegetables, unpasteurized milk or other dairy products such as cheese, and undercooked meat or fish may all be contaminated and should be avoided. Fish, especially reef fish, red snapper, and barracuda, are of particular concern, because they can contain toxins. Breast-feeding should be encouraged for young children, especially infants <6 mo of age.

Insect-Borne Infections

Insect-borne infections for which traveling children are at risk include malaria, yellow fever, dengue, Japanese encephalitis, filariasis, trypanosomiasis, and onchocerciasis, depending on the area of travel. Malaria, yellow fever, Japanese encephalitis, and filariasis are typically caused by night-biting mosquitoes, whereas dengue is usually caused by day-biting mosquitoes.

Exposure to insect bites can be avoided by restricting high-risk activities, staying indoors in a screened and protected area from dusk to dawn, wearing appropriate attire, and using insect repellents containing permethrin or N,N-diethyl-m-toluamide (DEET). Rare instances of toxic encephalopathy have been reported in young children with exposure to high concentrations of DEET, but use of repellent with no more than 40% DEET and avoidance of repeated applications as well as avoiding application to mucous membranes minimize the risk of this complication. Concentrations of 25-35% DEET, to be applied every 4-6 hours as needed, are recommended for children, although longer-acting DEET products are available.

For infants, the parent should apply the repellant to the parent’s hands and then transfer it to the infant, avoiding the infant’s hands and face. Immobile young infants can also be protected by a microenvironment: chemically treated netting placed over car seats, strollers, or carriers. The American Academy of Pediatrics (AAP) recommends avoiding the use of DEET in infants <2 mo of age, given increased skin permeability.

Spraying clothing with permethrin, a synthetic pyrethroid, is a safe and effective method of reducing insect bites in children. Permethrin-sprayed clothes remain effective for ≥2 wk, even with laundering. Bed nets, particularly permethrin-impregnated bed nets, also decrease the risk of insect bites, and their use is highly recommended.

Infections from Contact with Infected Persons or Through Needle Exposure

Many of the infections that may be acquired by children traveling internationally through contact with other individuals are preventable by routine childhood immunizations. Other diseases transmitted through human contact include viral respiratory and GI infections, viral hepatitis, tuberculosis (TB), and sexually transmitted diseases, including HIV infection. Adolescent travelers should be reminded that sexual encounters and needle or blood exposure (including tattooing and body piercing) carry a significant risk of HIV and hepatitis infection. Systematic screening of blood donations for HIV and other bloodborne infections is not yet feasible in many developing countries, so the safety of transfusion services in these countries cannot be ensured. Travelers might wish to have their blood typed before departure to determine whether family members or travel companions have compatible blood types and might be able to donate blood for transfusion in an emergency.

Infections from Infected Animals or Environments

Infections potentially acquired from contact with animals include rabies from stray dogs and plague from rodents. Swimming or diving in contaminated water can result in serious injury and increase the risk of infections such as schistosomiasis, leptospirosis, and primary amebic meningoencephalitis. Proper footwear at all times as well as using a barrier such as a towel to play on the ground should be emphasized, because some parasitic infections, such as hookworm, are transmitted from the soil directly through exposed skin.

Diphtheria, Tetanus, and Pertussis

Diphtheria is endemic in many developing countries. After the disintegration of the Soviet Union in 1991, diphtheria re-emerged in the new independent states, highlighting the potential for new outbreaks under the right circumstances. Tetanus is a major cause of worldwide neonatal mortality and is most prevalent in tropical countries. Pertussis is common in developing countries and in some developed nations where pertussis immunization is less widespread than in the USA because of earlier concerns about the pertussis vaccine’s adverse effects. The incidence of pertussis also appears to be increasing in the USA with concern of waning immunity in adolescents and adults. Children traveling internationally should be up to date on diphtheria and tetanus toxoids and acellular pertussis (DTaP) immunization with completion of 5 doses by 4-6 yr of age. A single dose of an adolescent preparation of tetanus and diphtheria toxoids and acellular pertussis (TdaP) vaccine is recommended at 11-12 yr of age for those who have completed the recommended diphtheria, tetanus toxoids, and pertussis (DTP)/DTaP series and have not received a tetanus-diphtheria (Td) booster dose. Adolescents 13-18 yr of age and adults who have completed the DTP/DTaP series, have never received Tdap, and in whom it has been 5 yr or more since their last Td booster dose also should receive a single dose of TdaP.

Infants and children <7 yr old who have not completed the series may be immunized using an accelerated schedule in preparation for international travel (see Fig. 165-4). There is some protection after 2 doses 4 wk apart, but there is little benefit with only 1 dose.

Haemophilus Influenzae Type B

H. influenzae type b remains the leading cause of meningitis in children 6 mo to 3 yr of age in many developing countries. Before they travel, all unimmunized children <60 mo of age and all children with chronic illness at risk for H. influenzae type b infections should be vaccinated (Chapter 165). If a child <15 mo is unvaccinated, ≥2 doses 4 wk apart starting no younger than 6 wk of age should be given before travel. Between 15 and 59 mo, 1 dose should be given. Unvaccinated children >59 mo of age do not need vaccination unless they are at risk due to an immunosuppressive condition.

Hepatitis B

Hepatitis B is highly prevalent in eastern and southeastern Asia, sub-Saharan Africa, and the Pacific basin. In certain parts of the world, 8-15% of the population may be chronically infected. Disease can be transmitted via blood transfusions not screened for hepatitis B surface antigen, exposure to unsterilized needles, close contact with local children who have open skin lesions, and sexual exposure. Exposure to hepatitis B is more likely for travelers residing for prolonged periods in endemic areas. Partial protection may be provided by 1 or 2 doses, but ideally 3 doses should be given before travel. See Figure 165-4 for the accelerated schedule. For unvaccinated adolescents, the first 2 doses are 4 wk apart, followed by a third dose 4-6 mo after the second one.

Measles, Mumps, and Rubella

Measles is still endemic in many developing countries and in some industrialized nations. Measles vaccine, preferably in combination with mumps and rubella vaccines (MMR), should be given to all children at 12-15 mo of age and at 4-6 yr of age, unless there is a contraindication (Chapter 165). In children traveling internationally, the second vaccination can be given as soon as 4 wk after the first. In the accelerated schedule, the first MMR vaccination can be given to children as young as 6 mo of age, but if the vaccine is given earlier than 12 mo of age, the child should be considered unvaccinated and given 2 additional doses ≥4 wk apart after 12 mo of age (see Fig. 165-4). Infants <6 mo of age are protected by maternal antibodies. HIV-infected children who travel abroad should be vaccinated unless they are severely immunocompromised (Chapter 268), because measles in HIV-infected children can be a devastating illness.

Pneumococcus

Streptococcus pneumoniae is the leading cause of bacterial pneumonia and among the leading causes of bacteremia and bacterial meningitis in children in developing and industrialized nations. Immunization against S. pneumoniae with a protein-conjugated pneumococcal vaccine is now part of routine childhood immunization in the USA. Unimmunized children should be immunized if they are at high risk, such as children with sickle cell disease, asplenia, HIV infection, congenital immunodeficiency, nephrotic syndrome, or chronic cardiac or pulmonary disease and those on immunosuppressive medication (Chapter 165). The Advisory Committee on Immunization Practices (ACIP) recommends that these children receive both the conjugate pneumococcal vaccine and the 23-valent polysaccharide vaccine ≥8 wk after the last conjugate vaccine dose. The ACIP also recommends that vaccination with conjugate pneumococcal vaccine be considered in all healthy unimmunized children 24-59 mo of age with 1 dose; conjugate pneumococcal vaccination of unimmunized children in this age group traveling internationally should be strongly considered for unvaccinated children between 6 wk and 12 mo of age should receive 2-3 doses of conjugate pneumococcal vaccine (depending on the age when starting the series) ≥4 wk apart with a booster at age 12-15 mo. For unvaccinated children ages 12-23 mo, 2 doses should be given ≥8 wk apart.

Poliomyelitis

Poliomyelitis was eradicated from the Western hemisphere in 1991 but remains endemic in several developing countries, and the 2004 epidemic in Nigeria underscored the importance of vaccination for preventing this disease. The poliovirus vaccination schedule in the USA is now a 4-dose, all-inactivated poliovirus (IPV) regimen (Chapter 165). Oral poliovirus vaccine (OPV) is no longer available in the USA. Unvaccinated adults who are at increased risk for exposure to poliovirus and who cannot complete the recommended IPV regimen (0, 1-2, and 6-12 mo) should receive 3 doses of IPV given ≥4 wk apart. For an accelerated dosing schedule for children, see Figure 165-4. Length of immunity conferred by IPV immunization is not known; a single booster dose of IPV is recommended for fully vaccinated adults traveling to endemic areas. Proof of vaccination is required to enter Saudi Arabia for the Hajj.

Rotavirus

Rotavirus is the most common cause of diarrhea in children worldwide. Rotavirus gastroenteritis causes approximately 500,000 deaths per year among children <5 yr of age in low- and middle-income countries. Two rotavirus vaccines, Rotateq (RV5) and Rotarix (RV1), are licensed for use in U.S. infants. RV5 is given orally at ages 2, 4, and 6 mo. RV1 is given orally at ages 2 and 4 mo. The minimum age for the first dose of rotavirus vaccine is 6 wk; the maximum age for the first dose is 14 wk, 6 days. Vaccination should not be started in infants age 15 wk, 0 days or older because there is not adequate data on the safety of starting rotavirus vaccine in infants older than 15 wk. The minimum interval between doses of rotavirus vaccine is 4 wk. All doses should be administered by age 8 mo, 0 days.

Varicella

All children ≥12 mo of age who have no history of varicella vaccination or chickenpox should be vaccinated unless there is a contraindication to vaccination (Chapter 165). Infants <6 mo of age are generally protected by maternal antibodies. All children now require 2 doses, the first at 12 mo of age, and the second at 4-6 yr of age. The second dose can be given as soon as 3 mo after the first dose. For unvaccinated children ≥13 yr of age, the first and second doses can be separated by 4-8 wk.

Cholera

Cholera is present in many developing countries, but the risk for infection among travelers to these countries is very low. However, there has been a resurgence of disease, with a 79% worldwide increase noted in 2006, Africa being the most affected. No cholera vaccine is currently available in the USA. No country or territory currently requires cholera vaccination, but rarely a local authority requires documentation of vaccination. A letter of exemption for medical reasons from a physician can suffice. Three newer oral live cholera vaccines are licensed for use in some countries, including one that is available in Canada and many European countries for use in children ≥2 yr of age and that appears to be safe and effective against most cholera strains. However, these cholera vaccines have little application to travelers unless prolonged trips to areas with poor sanitation are planned.

Hepatitis A

Hepatitis A virus is endemic in most of the world, and travelers are at risk, even if their travel is restricted to the usual tourist routes. Hepatitis A infection can occur as a result of eating shellfish harvested from sewage-contaminated waters, eating unwashed vegetables or fruits, or eating food prepared by an asymptomatic carrier of hepatitis A virus. Young children infected with hepatitis A are often asymptomatic but can transmit infection to older children and adults, who are more likely to develop clinical hepatitis. Few areas carry no risk of this infection, and therefore immunization or IG is recommended for all traveling children.

Hepatitis A vaccine is recommended in the USA for universal immunization of all children ≥12 mo of age, administered as 2 doses 6 mo apart. Vaccination is especially important for children traveling to countries with intermediate or high hepatitis A endemicity (areas other than the USA, Canada, Australia, New Zealand, Japan, Western Europe, and Scandinavia). Protective immunity develops 2-4 wk after receiving the initial vaccine dose. A combined 3-dose hepatitis A and hepatitis B vaccine is now available in the USA but is licensed for use only in adults >18 yr of age.

Children <1 year of age and children who will be traveling to an endemic area within 2 wk should receive intramuscular IG. For short-term protection (1-2 mo), 0.02 mL/kg of IG is given IM; for long-term protection (3-5 mo), 0.06 mL/kg of IG is given IM and repeated every 5 mo while exposure to hepatitis A continues. IG can be administered at the same time as the inactivated vaccine but should be given at a separate site and in a separate syringe. If a child requires MMR or varicella immunization, these live-attenuated viral vaccines should be given either 2 wk before or 3 mo after IG administration.

Influenza and Avian Influenza

The risk for exposure to influenza during international travel varies depending on the time of year, destination, and intermingling of persons from different parts of the world where influenza may be circulating. In tropical areas influenza can occur throughout the year, whereas in the temperate regions of the Southern hemisphere, most activity occurs from April through September. In the Northern hemisphere, influenza generally occurs from November through March. Influenza vaccination is strongly recommended for children ≥6 mo to 5 yr old and all other children who are at increased risk for complications of influenza, including those with chronic medical conditions (chronic cardiac, renal, or pulmonary disease, immunosuppressive conditions or therapy, HIV infection, sickle cell disease, and diabetes mellitus) (Chapter 165). The AAP now recommends universal immunization for all healthy children from 6 mo to 18 yr old. The live-attenuated vaccine (administered nasally) can be given to healthy children. However, the list of medical contraindications to this vaccine should be reviewed carefully (Chapter 165). Children with any of these conditions should receive only the inactivated vaccine.

Currently, there is no available vaccine effective against avian influenza, the H5N1 virus, which has become an increasing concern worldwide. However, there are precautions for those traveling to endemic areas, which include parts of Asia, Africa, Eastern Europe, and the Middle East (see the CDC’s website for a detailed list of countries). Because H5N1 influenza is spread through contact with infected birds, these precautions include avoiding direct contact with birds or surfaces with bird droppings, avoiding poultry farms or bird markets, eating only well-cooked bird meat or products, and washing hands frequently. Human-to-human transmission has been reported but is very rare and has not involved spread past one person. Oseltamivir is the antiviral of choice to treat avian influenza, because the virus is resistant to amantidine and rimantidine. Oseltamivir can be given to children 1 year of age and older. Some resistance to oseltamivir has been reported.

Japanese Encephalitis

Japanese encephalitis is a disease transmitted by mosquitoes in rural areas of Asia, where people are in close proximity to livestock. Asymptomatic cases outnumber symptomatic cases by ≥200 to 1. With symptomatic disease, the fatality rate is 10-70% and the incidence of neurologic sequelae in survivors is 50%. The risk of disease in travelers is <1 case per million travelers but is highest in children. The disease occurs primarily from June to September in temperate zones and throughout the entire year in tropical zones. Vaccination is recommended for travelers planning visits of >1 month to rural areas of Asia, where the disease is endemic, especially areas of rice or pig farming. Vaccination is recommended for shorter visits to such areas if the traveler will often be outdoors (e.g., camping or hiking). Risk for infection can be greatly reduced by following the standard precautions to avoid mosquito bites. Parents of very young children should be discouraged from traveling with their children to high-risk areas.

The inactivated Japanese encephalitis vaccine has an efficacy of >95%, but hypersensitivity reactions occur in up to 0.6% of vaccine recipients; 1 in 1,000 vaccines have urticarial reactions or facial or oropharyngeal angioedema that can occur within minutes or up to 2 wk after vaccination. The series should be completed 2 wk before travel so that any adverse reactions to the vaccine can be observed and treated. The series usually is given over 1 mo, but an accelerated course can be given over 14 days, although neutralizing antibody titers tend to be lower with the accelerated course than with the normal course.

Meningococcus

Neisseria meningitidis causes epidemic and endemic disease worldwide (Chapter 184).

Most cases occur in the “meningitis belt” of sub-Saharan Africa (see the map at www.cdc.gov/travel/yellowbook/2008/ch4/menin.aspx) between December and June. Epidemics have also occurred in the Indian subcontinent and Saudi Arabia, especially among pilgrims to the Hajj. Cases in American travelers are rare, and vaccination is indicated primarily in travelers to an area with an active outbreak or those who might have prolonged contact with the local population in an endemic area, especially in crowded conditions. Saudi Arabia requires all pilgrims to Mecca to have documentation of meningococcal vaccination ≥10 days and within 3 yr before arrival. Serogroup A is the most common cause of epidemics outside the USA, but serogroup C and, rarely, serogroup B have also been associated with epidemics.

There are currently 2 forms meningococcal vaccine available in the USA: a quadrivalent polysaccharide A/C/Y/W-135 vaccine and quadrivalent conjugate A/C/Y/W-135 vaccines. Immunization with a quadrivalent protein conjugate vaccine is now part of routine vaccine recommendations for children 11-18 yr old. If a conjugate vaccine is not available, the quadrivalent polysaccharide vaccine is recommended for children ≥2 yr of age who are at risk for meningococcal disease caused by a vaccine serogroup. It can also be used for children ≥3 mo of age who are at risk for serogroup A meningococcal disease, because the vaccine provides some protection against this serotype but not the other 3 at this age. The vaccine is ineffective against serogroup A in infants <3 mo of age and may be only partially effective against this serogroup in children 3-11 mo of age; it does not provide protection for children <2 yr of age against the other serogroups. Children vaccinated before 4 yr of age should be revaccinated after 2-3 yr if they remain in an endemic area.

Rabies

Rabies is endemic in many countries in Africa, Asia, and Central and South America. Children are at particular risk because they are less likely to report bites and because facial bites are more common in children. Pre-exposure prophylaxis should be considered if a child will be in an endemic area for longer than 1 month or will be traveling to an area where rapid, effective postexposure prophylaxis might not be available. An animal bite in a rabies-endemic area is a medical emergency. Immediate medical care should be sought at a facility that can administer appropriate postexposure rabies prophylaxis. If possible, the animal in question should be caught and quarantined for 10 days of observation for signs of rabies. Postexposure prophylaxis is required even for persons who received pre-exposure vaccination.

Three inactivated rabies vaccines are available in the USA for pre-exposure vaccination: human diploid cell vaccine (HDCV), rabies vaccine adsorbed (RVA), and purified chick embryo cell (PCEC) vaccine. Pre-exposure prophylaxis is given either intramuscularly (HDCV, RVA, or PCEC) as 3 doses (1 mL) on days 0, 7, and 21 or 28. Postexposure prophylaxis is given as 4 doses (1 mL) of HDCV, RVA, or PCEC vaccine intramuscularly on days 0, 3, 7, and 14 if previously unvaccinated and 2 doses (1 mL) intramuscularly on days 0 and 3 if previously vaccinated. Previously unvaccinated persons should also receive rabies immunoglobulin (RIG) (20 IU/kg, with as much of the dose as possible infiltrated around the wound site) at the time of initial postexposure prophylaxis. Previously vaccinated persons should not receive RIG. Children receiving mefloquine or chloroquine may have limited immune reactions to intradermal rabies vaccine and should be vaccinated intramuscularly. Purified cell culture–derived vaccines are not always available abroad; travelers should be aware that rabies vaccines derived from neural tissue carry an increased risk for adverse reactions, often with neurologic sequelae. Unpurified or purified equine RIG preparations are still used in some developing countries and are also associated with a higher risk for severe reactions, including serum sickness and anaphylaxis. If rabies prophylaxis is initiated abroad, neutralizing titers should be checked on return and immunization should be completed with a cell culture–derived vaccine.

Tuberculosis

The risk for TB in the typical traveler is low. All children traveling for prolonged periods to high-risk areas should have tuberculin skin testing done before and after travel. Immunization with BCG is controversial. It is not often used in the USA, but some authorities believe it should be given to children, especially infants, who will reside for a long time in an area with a high prevalence of TB or with multidrug-resistant TB, because it appears to be highly protective against meningeal and miliary TB in children.

Typhoid

Salmonella typhi infection, or typhoid fever, is common in many developing countries in Asia, Africa, and Latin America (Chapter 190). Typhoid vaccination is recommended for children traveling to the Indian subcontinent (the area of highest risk) and for persons traveling to endemic areas who are at higher risk for infection (visits >4 wk, backpackers, and travelers staying with friends or relatives in developing countries). Vaccination should be strongly considered for all children traveling to endemic areas, especially if exposure to contaminated food and water is likely.

Two typhoid vaccines, the intramuscular Vi-polysaccharide vaccine and oral Ty21a strain live-attenuated vaccine, are recommended for use in children in the USA. Both produce a protective response in 50-80% of recipients. The intramuscular Vi-polysaccharide vaccine is licensed for use in children 2 yr of age and older. It can be given any time before departure, but it should ideally be administered 1 mo or more before travel, with a booster needed 2-3 yr later. The oral Ty21a vaccine can only be used in children ≥6 yr of age and is given in 4 doses over a 1-week period: 1 enteric-coated capsule is swallowed whole with a cool drink, ≥1 hr before a meal, every other day until the 4 doses are completed. The oral vaccine is associated with an immune response for 5 yr. Antibiotics inhibit the immune response to the oral Ty21a vaccine; the vaccine should not be given within 24 hours of antibiotic treatment, and antibiotics should be avoided until 7 days after completing the vaccine series. Studies have demonstrated that mefloquine, chloroquine, and atovaquone-proguanil can be given concurrently with the oral Ty21a vaccine without affecting the immunogenicity of the vaccine. Oral Ty21a vaccine should not be given to immunocompromised children; these children should receive the intramuscular Vi-polysaccharide vaccine.

Yellow Fever

Yellow fever (Chapter 262) is a mosquito-borne viral illness resembling other viral hemorrhagic fevers (Chapter 263) but with more prominent hepatic involvement. Yellow fever is present in tropical areas of South America and Africa.

Yellow fever vaccination is indicated in children >9 mo of age traveling to an endemic area. Many countries require yellow fever vaccination by law for travelers arriving from endemic areas, and some African countries require evidence of vaccination from all entering travelers. Current recommendations can be obtained by contacting state or local health departments or the Division of Vector-Borne Infectious Diseases of the CDC (telephone: 404-332-4555; or website: www.cdc.gov/travel/yellowbook/2010/chapter-2/yellow-fever.aspx). Most countries accept a medical waiver for children who are too young to be vaccinated (<4 mo of age) and for persons with a contraindication to vaccination, such as immunodeficiency. Children with asymptomatic HIV infection may be vaccinated if exposure to yellow fever virus cannot be avoided.

Yellow fever vaccine (0.5 mL SC), a live-attenuated vaccine (17D strain) developed in chick embryos, is safe and highly effective in children >9 mo of age, but in young infants it is associated with an increased risk for encephalitis (0.4%) and other severe reactions. Yellow fever vaccine should never be administered to infants <6 mo of age; infants 6-8 mo of age should be vaccinated only in consultation with the CDC. In children >9 mo old, adverse effects are rare, although neurotropic and viscerotropic disease associated with the vaccine have been reported. The risk of these reactions is higher in those with thymus disease, and those >60 yr old (and <9 mo of age as above for neurotropic disease).

Children with a history of anaphylactic reactions to eggs should not receive yellow fever vaccine. Children with an egg allergy who must be given the vaccine should receive desensitization therapy. Long-lived, perhaps lifetime, immunity develops with this vaccine; however, international travel certificates require proof of immunization within 10 yr.