Chapter 3Infectious Diseases Related To Travel
James P. Alexander, Gregory S. Wallace, Steven G. F. Wassilak
The infectious agent is poliovirus (genus Enterovirus) types 1, 2, and 3. Polioviruses are small (27–30 nm), nonenveloped viruses with capsids enclosing a single-stranded, positive-sense RNA genome about 7,500 nucleotides long. Most of the properties of polioviruses are shared with the other enteroviruses.
MODE OF TRANSMISSION
Polioviruses are spread through fecal-oral or oral transmission. Acute infection involves the oropharynx, gastrointestinal tract, and occasionally the central nervous system.
In the prevaccine era, infection with poliovirus was common worldwide, with seasonal peaks and epidemics in the summer and fall in temperate areas. The incidence of poliomyelitis in the United States declined rapidly after the licensure of inactivated polio vaccine (IPV) in 1955 and live oral polio vaccine (OPV) in the 1960s. The last cases of indigenously acquired polio in the United States occurred in 1979. The Global Polio Eradication Initiative (GPEI) subsequently eliminated polio in the Americas, where the last wild poliovirus (WPV)-associated polio case was detected in 1991.
In 1999, a change in vaccination policy in the United States from use of OPV to exclusive use of IPV eliminated the 8–10 vaccine-associated paralytic poliomyelitis (VAPP) cases that had occurred annually since the introduction of OPV in the 1960s. In the United States, 2 events in 2005 highlighted the continuing but low risk for poliovirus infection for unvaccinated people, whether residing in the United States or traveling:
- A case of imported VAPP occurred in an unvaccinated US adult who had traveled abroad, likely from contact with an infant recently vaccinated with OPV.
- An unvaccinated, immunocompromised infant and 4 children in 2 other families in the same small rural community were found to be asymptomatically infected with a vaccine-derived poliovirus, presumably originating outside the United States in a country that uses OPV.
GPEI has built upon the success in the Americas and made great progress in eradicating WPVs, reducing the number of reported polio cases worldwide by more than 99% since the mid-1980s. Wild poliovirus circulation has never been interrupted in only 3 countries: Afghanistan, Nigeria, and Pakistan. In spite of progress made in eradicating WPVs globally, countries are still at risk for imported cases, primarily from these 3 countries. From 2008 through 2010, WPV outbreaks from importations have occurred in 28 countries in Africa, Eastern Europe and North Asia, and South Asia. In 4 of these countries (Angola, Chad, Democratic Republic of the Congo, and southern Sudan), WPV transmission has been reestablished.
Because of polio eradication efforts, the number of countries where travelers are at risk for polio has decreased dramatically. The last documented case of WPV-associated paralysis in a US resident travelling abroad occurred in 1986 in a 29-year-old vaccinated adult who had been traveling in South and Southeast Asia. As noted above, in 2005 an unvaccinated US adult traveling abroad acquired VAPP after contact with an infant recently vaccinated with OPV.
At the time of publication, most of the world’s population resides in areas considered free of WPV circulation, including the Western Hemisphere, the Western Pacific region (which encompasses China), and most of Europe. Vaccination is recommended for all travelers to polio-endemic or epidemic areas, including countries with recent proven WPV circulation and neighboring countries. As of October 2010, these areas include some but not all countries in East, Central and West Africa, Eastern Europe and Northern Asia, and South Asia. For current information on the status of polio eradication efforts and vaccine recommendations, consult the travel notices on the CDC Travelers’ Health website (www.cdc.gov/travel) or the GPEI website (www.polioeradication.org).
Clinical manifestations of poliovirus infection range from asymptomatic (most infections) to symptomatic, including acute flaccid paralysis of a single limb to quadriplegia, respiratory failure, and rarely, death.
The diagnosis is made by identifying poliovirus in clinical specimens (usually stool) obtained from an acutely ill patient. Poliovirus may be detected by culture on appropriate cell lines followed by identification by neutralization tests or by PCR. Poliovirus may also be identified by direct amplification from stool specimens followed by partial genomic sequencing to establish identity and possible source of the virus. Shedding in fecal specimens can be intermittent, but usually poliovirus can be detected for up to 4 weeks after onset of illness. During the first 3–10 days of the illness, poliovirus can also be detected from oropharyngeal specimens. Poliovirus is rarely detected in the blood or cerebrospinal fluid.
Only treatment for symptoms is available, ranging from pain and fever relief to intubation and mechanical ventilation for patients with respiratory insufficiency.
PREVENTIVE MEASURES FOR TRAVELERS
In the United States, infants and children should be vaccinated against polio as part of a routine immunization series (see Infants and Children below). Before traveling to areas where poliomyelitis cases are still occurring, travelers should ensure that they have completed the recommended age-appropriate polio vaccine series and have received a booster dose, if necessary (see Infants and Children and Adults below). To eliminate the risk for VAPP, since 2000, IPV has been the only polio vaccine available in the United States; however, OPV continues to be used in many countries and for global polio eradication activities.
Infants and Children
In the United States, all infants and children should receive 4 doses of IPV at ages 2, 4, and 6–18 months and 4–6 years. The final dose should be administered at age ≥4 years, regardless of the number of previous doses, and should be given ≥6 months after the previous dose. A fourth dose in the routine IPV series is not necessary if the third dose was administered at age ≥4 years and ≥6 months after the previous dose. If both OPV and IPV were administered as part of the routine series, a combined total of 4 doses should be administered, regardless of the child’s age. If the routine series cannot be administered within the recommended intervals before protection is needed, the following alternatives are recommended:
- The first dose should be given to infants ≥6 weeks old.
- The second and third doses should be administered ≥4 weeks after the previous doses.
- The minimum interval between the third and fourth doses is 6 months.
If the age-appropriate series is not completed before departure, the remaining IPV doses to complete a full series should be administered when feasible, at the intervals recommended above, if the child remains at increased risk for poliovirus exposure.
Adults who are traveling to areas where poliomyelitis cases are still occurring and who are unvaccinated, incompletely vaccinated, or whose vaccination status is unknown should receive 2 doses of IPV administered at an interval of 4–8 weeks; a third dose should be administered 6–12 months after the second. If 3 doses of IPV cannot be administered within the recommended intervals before protection is needed, the following alternatives are recommended:
- If >8 weeks is available before protection is needed, 3 doses of IPV should be administered ≥4 weeks apart.
- If <8 weeks but >4 weeks is available before protection is needed, 2 doses of IPV should be administered ≥4 weeks apart.
- If <4 weeks is available before protection is needed, a single dose of IPV is recommended.
If <3 doses are administered, the remaining IPV doses to complete a 3-dose series should be administered when feasible, at the intervals recommended above, if the person remains at increased risk for poliovirus exposure. Adults who have completed a routine series of polio vaccine are considered to have lifelong immunity to poliomyelitis, but data are lacking. As a precaution, adults (≥18 years of age) who are traveling to areas where poliomyelitis cases are occurring and who have received a routine series with either IPV or OPV in childhood should receive another dose of IPV before departure. For adults, available data do not indicate the need for more than a single lifetime booster dose with IPV.
Vaccine Safety and Adverse Reactions
Minor local reactions (pain and redness) can occur with IPV. No serious adverse reactions to IPV have been documented. IPV should not be administered to people who have experienced a severe allergic reaction (anaphylaxis) after a previous dose of IPV or after receiving streptomycin, polymyxin B, or neomycin, which IPV contains in trace amounts; hypersensitivity reactions can occur after IPV administration among people sensitive to these 3 antibiotics.
Pregnancy and Breastfeeding
If a pregnant woman is unvaccinated or incompletely vaccinated and requires immediate protection against polio because of planned travel to a country or area where polio cases are occurring, IPV can be administered as recommended for adults. Breastfeeding is not a contraindication to vaccination of an infant or mother against polio.
Precautions and Contraindications
IPV may be administered to people with diarrhea. Minor upper respiratory illnesses with or without fever, mild to moderate local reactions to a previous dose of IPV, current antimicrobial therapy, and the convalescent phase of acute illness are not contraindications for vaccination.
IPV may be administered safely to immunodeficient travelers and their household contacts. Although a protective immune response cannot be ensured, IPV might confer some protection to the immunodeficient person. People with certain primary immunodeficiency diseases should not be given OPV and should avoid contact with excreted OPV virus (such as exposure to a child vaccinated with OPV in the previous 6 weeks); however, this situation no longer occurs in the United States unless a child receives OPV overseas.
- Alexander JP, Ehresmann K, Seward J, Wax G, Harriman K, Fuller S, et al. Transmission of imported vaccine-derived poliovirus in an undervaccinated community in Minnesota. J Infect Dis. 2009 Feb 1;199(3):391–7.
- Alexander LN, Seward JF, Santibanez TA, Pallansch MA, Kew OM, Prevots DR, et al. Vaccine policy changes and epidemiology of poliomyelitis in the United States. JAMA. 2004 Oct 13;292(14):1696–701.
- CDC. Certification of poliomyelitis eradication—the Americas, 1994. MMWR Morb Mortal Wkly Rep. 1994 Oct 7;43(39):720–2.
- CDC. Immunization schedules. Atlanta: CDC; 2010 [cited 2010 Apr 6]. Available from: http://www.cdc.gov/vaccines/recs/schedules/default.htm.
- CDC. Imported vaccine-associated paralytic poliomyelitis—United States, 2005. MMWR Morb Mortal Wkly Rep. 2006 Feb 3;55(4):97–9.
- CDC. Laboratory surveillance for wild and vaccine-derived polioviruses—worldwide, January 2008–June 2009. MMWR Morb Mortal Wkly Rep. 2009 Sep 4;58(34):950–4.
- CDC. Poliomyelitis. In: Atkinson W, Hamborsky J, McIntyre L, Wolfe S, editors. Epidemiology and Prevention of Vaccine-Preventable Diseases. 9th ed. Washington, DC: Public Health Foundation; 2006. p. 97–110.
- CDC. Poliomyelitis—United States, 1975–1984. MMWR Morb Mortal Wkly Rep. 1986 Mar 21;35(11):180–2.
- CDC. Progress toward interruption of wild poliovirus transmission—worldwide, 2009. MMWR Morb Mortal Wkly Rep. 2010 May 14;59(18):545–50.
- CDC. Update on vaccine-derived polioviruses—worldwide, January 2008–June 2009. MMWR Morb Mortal Wkly Rep. 2009 Sep 18;58(36):1002–6.
- CDC. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding routine poliovirus vaccination. MMWR Morb Mortal Wkly Rep. 2009 Aug 7;58(30):829–30.
- CDC. Wild poliovirus type 1 and type 3 importations—15 countries, Africa, 2008–2009. MMWR Morb Mortal Wkly Rep. 2009 Apr 17;58(14):357–62.
- Plotkin SA, Vidor E. Vaccine-inactivated. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. 5th ed. Philadelphia: Saunders Elsevier; 2008. p. 605–30.
- Prevots DR, Burr RK, Sutter RW, Murphy TV. Poliomyelitis prevention in the United States. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2000 May 9;49(RR-5):1–22.
- Sutter RW, Kew OM, Cochi SL. Poliovirus vaccine- live. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. Philadelphia: Saunders Elsevier; 2008. p. 631–86.
- World Health Organization. Wild poliovirus weekly update. World Health Organization; 2010 [updated 2010 Mar 6; cited 2010 Apr 6]. Available from: http://www.polioeradication.org/casecount.asp.
- WHO Advisory Committee. Conclusions and recommendations of the Advisory Committee on Poliomyelitis Eradication, Geneva, 27–28 November 2007. Wkly Epidemiol Rec. 2008 Jan 18;83(3):25–35.
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