POLIOVIRUS INFECTION, NONPARALYTIC

Wisconsin Division of Public Health Disease Surveillance Manual (EpiNet, March 2008)

I. IDENTIFICATION

A. CLINICAL DESCRIPTION: Most poliovirus infections are asymptomatic or cause mild febrile disease. Poliovirus infections occasionally cause aseptic meningitis and one out of 200 infections from poliovirus type 1 results in paralytic poliomyelitis, characterized by acute onset of flaccid paralysis that is typically asymmetric and associated with a prodromal fever. Poliovirus is spread through fecal material, oral secretions, some aerosols and fomites.

*Note that this case definition applies only to poliovirus infections found in asymptomatic persons or those with mild, nonparalytic disease (e.g., those with a nonspecific febrile illness, diarrhea, or aseptic meningitis). Isolation of polioviruses from persons with acute paralytic poliomyelitis should continue to be reported as “paralytic poliomyelitis.”

Background: In 2005, a vaccine-derived poliovirus (VDPV) type 1 was identified in a stool specimen obtained from an immunodeficient Amish infant and, subsequently, from 4 other children in 2 other families in the infant’s central Minnesota community1. Epidemiological and laboratory investigations determined that the VDPV had been introduced into the community about 3 months before the infant was identified and that there had been virus circulation in the community. Investigations in other communities in Minnesota and nearby states and Canada did not identify any additional infections or any cases of paralytic poliomyelitis.

Although OPV is still widely used in most countries, inactivated poliovirus vaccine (IPV) replaced OPV in the United States in 20002. Therefore, the Minnesota poliovirus infections were the result of importation of a vaccine-derived poliovirus into the United States and the first time a VDPV has been shown to circulate in a community in a developed country3. Circulating VDPVs commonly revert to a wild poliovirus phenotype and is the underlying cause of the rare cases of vaccine-associated paralytic poliomyelitis (VAPP) in OPV recipients and their close contacts.3 Contacts between persons in communities with low polio vaccination coverage pose the potential for transmission of polioviruses and outbreaks of paralytic poliomyelitis.

Because of the success of the routine childhood immunization program in the U.S. and the Global Polio Eradication Initiative, polio has been eliminated in the Americas since 1991. Because the U.S. has used IPV exclusively since 2000, the occurrence of any poliovirus infections in the U.S. is a cause for concern. Reflecting the global concern for poliovirus importations into previously polio-free countries, the World Health Assembly, W.H.O., has added circulating poliovirus to the notifiable events in the International Health Regulations (IHR)4.

B. REPORTING CRITERIA: Isolation of polio virus from a person who is asymptomatic or has mild, nonparalytic disease.

C. LABORATORY CRITERIA FOR CONFIRMATION:
Poliovirus isolate identified in an appropriate clinical specimen (e.g., stool, cerebrospinal fluid, oropharyngeal secretions), with confirmatory typing and sequencing performed by the CDC Poliovirus Laboratory, as needed.

D. WISCONSIN CASE DEFINITION:

• Confirmed: Poliovirus isolate identified in an appropriate clinical specimen (e.g., stool, cerebrospinal fluid, oropharyngeal secretions), with confirmatory typing and sequencing performed by the CDC Poliovirus Laboratory, as needed.
• Probable: none
• Suspected: none

II. ACTIONS REQUIRED / PREVENTION MEASURES

A. WISCONSIN DISEASE SURVEILLANCE CATEGORY I: Report IMMEDIATELY BY TELEPHONE to the patient's local health officer upon identification of a case or suspected case. Complete and mail an Acute and Communicable Disease Case Report (DPH 4151) to the local health officer within 24 hours.

B. EPIDEMIOLOGY REPORTS REQUESTED: Acute and Communicable Diseases Case Report (DPH 4151).

C. PREVENTION MEASURES:

• All children should routinely receive four doses of inactivated polio vaccine (IPV) at ages 2, 4, and 6–18 months and 4–6 years.
• Routine poliovirus vaccination of adults (i.e., persons aged >18 years) residing in the United States is not necessary. Most adults have a minimal risk for exposure to polioviruses in the United States and most are immune as a result of vaccination during childhood or exposure to wild virus during the pre-vaccine era. Vaccination is recommended for certain adults who are at greater risk for exposure to polioviruses than the general population, including the following persons:
• Travelers to areas or countries where polio is epidemic or endemic.
• Members of communities or specific population groups with disease caused by wild polioviruses.
• Laboratory workers who handle specimens that might contain polioviruses.
• Health-care workers who have close contact with patients who might be excreting wild polioviruses.
• Unvaccinated adults whose children will be receiving oral poliovirus vaccine.
• Identify communities with low vaccination coverage, assess current vaccination status and offer IPV.

D. PUBLIC HEALTH INTERVENTIONS:

• Contact the Immunization Program and/or the State Epidemiologist for Communicable Diseases for technical assistance and consultation. An epidemiologic investigation will be necessary to identify the source of infection, persons to whom infection may have spread, specimens to collect and exposed susceptible persons to whom IPV should be offered.

III. CONTACTS FOR CONSULTATION

A. BCDP / IMMUNIZATION PROGRAM: (608) 266-2346.

B. REGIONAL STAFF: See Epinet Introduction: “REGIONAL OFFICE CONTACTS”.

C. WSLH / VIROLOGY: (608) 262-1021.

IV. RELATED REFERENCES

1. CDC. Poliovirus infections in four unvaccinated children – Minnesota, August-October 2005. MMWR; 54(41); 1053–1055.
   
2. CDC. Poliomyelitis prevention in the United States. Updated recommendations from the Advisory Committee on Immunization Practices (ACIP). MMWR 2000;49(No. RR-5).
   
3. Kew OM, Sutter RW, de Gourville EM, Dowdle WR, Pallansch MA. Vaccine-derived polioviruses and the endgame strategy for global polio eradication. Ann Rev Microbiol 2005;59;587-635.
   
4. CDC. Brief report. Conclusions and recommendations of the Advisory Committee on Poliomyelitis Eradication — Geneva, Switzerland, October 2005. MMWR 2005;54;1186-8.
   
5. Centers for Disease Control.  DISSS Home. Alphabetical List of Case Definitions at: http://www.cdc.gov/ncphi/disss/nndss/casedef/poliovirus_nonparalytic.htm

V. DISEASE TRENDS

The last time poliovirus isolates were recovered in Wisconsin was 1999, one from a 6-month old and one from a 14-month old.  Both were presumed to be shedding vaccine virus.  In Wisconsin, the last three cases of wild virus-associated poliovirus were reported in 1979.