On July 7, 2007, the Department of Human Services (DHS) in Victoria, Australia, was notified of a suspected case of imported poliomyelitis in a 22-year-old man (a university student). The patient, who was studying in Melbourne, had returned home to Pakistan on March 13, 2007, and in early June, he visited Islamabad and the North-West Frontier Province. On June 22, 2007, fever, nausea, and pain in the lower back and legs developed and progressed to lower limb weakness. The symptoms appeared to resolve, and he returned to Melbourne, arriving on a flight from Bangkok, Thailand, on July 2, 2007. However, he remained at home with back pain and lower limb weakness and consulted a general practitioner on July 6, 2007. He was advised to go to a hospital, where the emergency department admitted him for further investigation. The patient reported receiving at least 3 doses of oral poliomyelitis vaccine as a child.

A case report describing the clinical features and treatment of the patient and the initial laboratory investigation was published by Stewardson et al. (5). Briefly, a magnetic resonance image of the patient’s spine, performed on July 7, indicated increased signal in the anterior horn cells, which is highly suggestive of poliomyelitis. The patient was placed in a single room with enteric precautions, and DHS was notified of the diagnosis of poliomyelitis. Although an initial pan-enterovirus reverse transcription–PCR (RT-PCR) performed directly on a fecal specimen collected on July 7 was reported as negative, the National Polio Reference Laboratory confirmed the diagnosis of poliomyelitis by isolation of non–Sabin-like poliovirus type 1 on July 13. The virus was subsequently reported to have high nucleic acid sequence identity with wild poliovirus isolates from Pakistan, which provided an epidemiologic link with the patient’s travel history. The index patient was placed in isolation in the hospital until 2 successive fecal specimens, collected 1 week apart, were negative for poliovirus by viral culture and RT-PCR (a total of 34 days).

DHS coordinated the public health response in the state of Victoria, while national and international responsibilities were handled by the Australian government Department of Health and Ageing. At the national level, this included liaising with the Communicable Diseases Network of Australia, the Australian Health Protection Committee, and the Public Health Laboratory Network. The case was one of the first reported to WHO under the International Health Regulations (2005), which came into effect in June 2007 and require member countries to notify WHO of poliomyelitis cases (6). On confirmation of the diagnosis of poliomyelitis, DHS performed a risk assessment for the potential infection of contacts of the index patient with wild poliovirus. Contacts were grouped as the following: 1) close contacts who resided with or visited the index patient’s residence, 2) fellow passengers on the airplane from Bangkok to Melbourne, 3) public contacts and staff at the general practitioner’s clinic, and 4) public contacts and healthcare workers (HCWs) at the hospital (Table 1).

Household contacts were judged to be at highest risk. Anyone who used the same toilet as the index patient before it had been cleaned was regarded as being at lesser risk, especially because the patient had not used a toilet to have a bowel movement either on the plane, at the general practitioner’s clinic, or at the hospital emergency department. In virtually all instances, the vaccination history of contacts was uncertain. Although the likelihood of transmission was deemed to be low, a cautious approach to the situation led to a comprehensive public health response.

The 2007 wild poliovirus importation generated widespread media coverage around Australia that assisted with contact tracing. However, tracing the passengers who disembarked with the index patient in Melbourne was difficult because of poor handwriting and inaccurate information on many of the arrival cards. This experience has implications for the urgent tracing of persons potentially exposed to other infectious diseases of public health significance, such as pandemic influenza. Despite extensive contact tracing, 26 (11%) of the 235 passengers could not be contacted. For the 96 passengers who chose to see their own doctor for vaccination and the 29 passengers who were contacted by letter or email, outcome is not known.

In large part, the laboratory investigation of the index patient and household contacts followed the procedures recommended by WHO for routine acute flaccid paralysis surveillance with collection of 2 fecal specimens obtained 24–48 hours apart, due to intermittent virus shedding, for virus culture (11). Virus cell culture was accepted by DHS as the approved standard for the test procedures, in agreement with the recommendation by WHO. This proved decisive because, for the first fecal specimen, enterovirus was not detected by RT-PCR performed directly on the specimen (5). RT-PCR is still a powerful tool for enterovirus detection as exemplified by the test results for the 2 positive CSF specimens. The testing, by cell culture and RT-PCR, of specimens from persons with suspected poliomyelitis and their contacts is recommended. This ensures that test results are determined by using the most rapid and sensitive methods available.

Household contacts of case-patients are at high risk of infection (12). We recommended that they be quarantined at home and that stool specimens be collected a minimum of 3 days after the first contact with the index patient to allow sufficient time for an infection to become established. As excretion of poliovirus in the feces can continue for several weeks (13,14), we sought advice from WHO and the Centers for Disease Control and Prevention (Atlanta, GA, USA) regarding when the index patient and the household contacts could be released from isolation and home quarantine, respectively. The criteria accepted by DHS was for 2 fecal specimens, collected 7 days apart for the index patient and >24 hours apart for the household contacts, to be negative for poliovirus isolation by cell culture (M. Pallansch, S. Roesel, pers. comm.).

The time taken to determine a negative result by cell culture leads to an inevitable delay in finalizing patient tests, which, in the circumstances described in this report, had implications for when the index patient and household contacts could be released from hospital isolation and home quarantine, respectively: 34 days for the index patient and 16 days for the household contacts. It should be noted that household quarantine of the contacts required substantial logistical support by DHS staff in terms of food and entertainment. This also has implications for large-scale quarantine as would be required in an influenza pandemic.

No published evidence is available on the role of polio vaccine as postexposure prophylaxis against paralytic disease. However, in persons with some preexisting immunity, which would include most of the Australian population, boosting the immune response with a single dose of oral polio vaccine or IPV is likely to reduce both pharyngeal and intestinal excretion of poliovirus in those who have been infected (15). The extent to which one undertakes tracing of contacts who used the same toilet was extensively debated by the Communicable Diseases Network Australia and the Australian Health Protection Committee. DHS opted to invite nonhousehold contacts to come to departmental offices or see their own physician for a booster dose of IPV and to be given information on the disease and its symptoms and signs as a precautionary measure. Booster doses of IPV have also been recommended for HCWs who have close contact with patients who might be excreting wild poliovirus (15). We followed this advice with the HCWs involved with the index patient, but issues arose in relation to the lack of immunization records, particularly with some of the overseas-born HCWs. We now advise that HCWs in close contact with an index patient with poliomyelitis, who have no recorded immunization history or who are not fully vaccinated, should provide 2 fecal specimens collected 24–48 hours apart and complete a course of vaccination with IPV, in accordance with the current Australian immunization guidelines (7).

Until this imported case, poliomyelitis caused by wild poliovirus had not been reported in Australia for 30 years. The case necessitated a rapid and extensive public health response. The age and vaccination history of the index patient highlight the need for public health officials worldwide to prepare for imported cases of suspected polio in persons of any age and with prior vaccination. The experience gained from the public health response to the importation in 2007, particularly in relation to tracing of contacts, isolation of cases, and quarantine of close contacts, has been incorporated into the national outbreak response plan for the investigation of cases of acute flaccid paralysis and suspected polio, published by the Australian government’s Department of Health and Ageing (16).