Vaccine Safety > Polio
Poliomyelitis Outbreak in the Dominican Republic and Haiti
FACT SHEET

• Overall message

• Poliomyelitis infection and illness

• Polio vaccine

• Poliomyelitis surveillance in the U.S.

Overall Message

Since July 12, 2000, 19 persons with acute flaccid paralysis (AFP) have been identified in the Dominican Republic.  These include six laboratory-confirmed cases with poliovirus type 1 isolates (wild type 1 poliovirus causes most of the AFP in countries where polio is still endemic).  All AFP cases were in children who were either unvaccinated or had received fewer than the four recommended doses.  In Haiti, a single case of laboratory-confirmed poliovirus type 1 has been reported to date.  The last reported case of AFP had a date of onset of November 18, 2000.

It appears that the outbreak virus is derived from oral polio vaccine (OPV).  This vaccine- derived virus has approximately 97% genetic identity to the parent vaccine strain, and appears to have recovered neurovirulence and transmissibility characteristics typical of wild poliovirus type 1.  Nucleotide sequencing suggests that the virus has been circulating for about 2 years.  The origin and continued circulation of this strain is in an area where routine vaccination coverage is low.

Because there is frequent travel between the United States and the Dominican Republic and Haiti, CDC has advised all State Health Departments to enhance their poliomyelitis surveillance, especially in communities with large immigrant populations from Haiti or the Dominican Republic.  CDC has issued a travel advisory recommending that all persons traveling to the Dominican Republic and Haiti be up-to-date on their polio vaccinations.  Adults should receive one lifetime booster of polio vaccine.  School-age children and adolescents who completed a primary series may receive an additional dose of IPV before travel.  Infants and children who are up-to-date on their routine immunization schedule and have at least two (preferably three) doses of poliovirus vaccine should be adequately protected.

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Key Points – Poliomyelitis Infection and Illness

1. Poliovirus is highly infectious among susceptible persons, with seroconversion rates of nearly 100% among susceptible household contacts of children, and higher than 90% among susceptible household contacts of adults.  Poliovirus is not passed easily in well-immunized communities. 
   
2. Poliovirus is spread via the fecal-oral route,  from one person to another by contaminated hands or objects.  It is also possible to spread poliovirus through respiratory secretions.

3. The incubation period for poliomyelitis ranges from 3 to 35 days.  Cases are most infectious from 7-10 days before and after the onset of symptoms, but poliovirus may be present in the stool for 3 to 6 weeks.

4. In most cases (72%), poliovirus infection is asymptomatic.  In other cases (24%), infection causes a viral syndrome with a few days of any combination of the following signs and symptoms:  fever, malaise, drowsiness, headache, nausea, vomiting, constipation, and sore throat.  Much less commonly, poliovirus infection presents as aseptic meningitis (4%), or as paralysis (#1%).
      
5. Paralytic poliomyelitis typically presents with rapid onset of flaccid paralysis and fever.  Paralysis progresses to its maximal extent within a few days, and usually progresses no further once fever resolves.  Paralysis is typically asymmetric, associated with decreased or complete loss of deep tendon reflexes and without involvement of sensory nerves.  Paralysis if not complete is usually more marked proximally.

6. The risk of contracting poliomyelitis in the United States is minimal because vaccination rates against polio are high.  The last outbreak of poliomyelitis in the United States caused by wild poliovirus occurred in 1979, and was among unimmunized communities in the Midwest. 

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Key Points – Polio Vaccine

1. Vaccinating with polio vaccine is the best way to prevent poliomyelitis.  Inactivated polio vaccine (IPV) currently is used in the United States.  Children receive a total of four doses of IPV.  A dose is given at 2 months, 4 months, 6-18 months, and 4-6 years of age.   Two doses and a booster of IPV are recommended for adults who are unvaccinated.

2. IPV is highly effective in producing immunity to poliovirus.  Ninety percent or more of vaccine recipients develop protective immunity to all three poliovirus types after two doses, and at least 99% are immune following three doses.
   
3. IPV is safe for most people.  Minor local reactions (pain, redness) may occur following IPV.  No serious adverse reactions to IPV have been recognized.  Because IPV contains trace amounts of streptomycin, polymyxin B, and neomycin, allergic reactions can occur among persons sensitive to these antibiotics.  IPV does not contain mercury preservative (thimerosal).  IPV does not contain live poliovirus, so it cannot cause polio.

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Key Points – Poliomyelitis Surveillance in the U.S.

1. CDC has advised health professionals that poliovirus infection be considered in the differential diagnosis of all patients presenting with acute flaccid paralysis.  Clinicians seeing such patients should obtain stool, throat, and cerebrospinal fluid for viral culture, and acute and convalescent serum to measure titers of neutralizing antibodies to poliovirus.  State Public Health authorities should be contacted immediately for additional instructions.
   
2. In areas where many persons travel between the United States and the Dominican Republic or Haiti, CDC recommends that patients with aseptic meningitis have stool and cerebrospinal fluid samples be obtained for viral culture.  Clinicians should report such patients to their State Health Department. 

This page last modified on December 14, 2000