Active Surveillance of Acute Flaccid Paralysis

Due to the lack of records it is not possible to have an idea about the date when poliomyelitis first become a notifiable disease in Macau. However, according to data from WHO, the last clinical case of paralytic poliomyelitis was reported in 1975.

The sensitivity of the passive surveillance system for poliomyelitis in Macau has been limited by the low index of diagnostic suspicion and the false sense of security that often occurs when a disease becomes rare. Thus active surveillance of AFP in children less than 15 years old should be initiated before January 1998 to screen for potential cases of poliomyelitis.

Active surveillance of AFP is a critical component of the polio eradication campaign in Macau and all over the world. By using an expected annual background incidence of approximately one case of AFP per 100,000 population less than 15 years in the absence of wild poliovirus transmission, AFP active surveillance serves as a good indicator of the level of monitoring for potential cases of paralytic poliomyelitis. Further, with the proper laboratory investigation of cases, AFP surveillance greatly improves the sensitivity for rapid detection of paralytic poliomyelitis.

In Macau, AFP active surveillance will be implemented through the collaborative effort between the Medical and Health Department, the Kiang Wu Hospital and the Virology Unit of Queen Mary Hospital in Hong Kong. Surveillance should be based on reporting through a specific monitoring program system, based in UTVE (Epidemiological Surveillance Technical Unit) and formed by a network of 2 general hospitals and 8 eight health centres, as well as reporting by pediatricians and general practitioners. A specialist integrating the territorial working group on polio eradication to rule out or confirm the diagnosis should evaluate all AFP cases.

It is expected that by the end of the year 2000 Macau, along with the rest of the WPR, should be formally certified as polio-free. Despite the probable elimination of indigenous wild poliovirus transmission, surveillance should be maintained until global eradication is achieved because of the risk of wild virus importation from endemic regions, for example, from the neighboring Guandong Province in China. Cases of paralytic poliomyelitis resulting from wild virus importation were never reported in Macau, probably due to the low sensitivity of the local surveillance system.

This protocol provides guidelines for investigating all suspected cases of paralytic poliomyelitis of any age, as well as AFP cases in children less than 15 years old. All suspected cases of paralytic poliomyelitis that meet the reporting criteria in this protocol - surveillance case definitions - should be reported according to the procedures outlined, to UTVE (by fax) and the Macau Sanitary Authority (Tap Seac or Islands health centres).

Guidelines are also provided for reporting the incidental finding of wild strain poliovirus, with or without any clinical symptoms. Relevant surveillance case definitions and diagnostic aids have been also included in the previous pages of this program, to facilitate the knowledge and development of the process.

The active surveillance of AFP can be divided into four main steps as presented in the specific flowchart.

Step 1: Screening of cases in all health units

Is the case clinically compatible with paralytic poliomyelitis or AFP, as defined previously?

If no: no further investigation or report is required.

If yes: the case should be reported to UTVE (by fax) and immediately referred to the Pediatrics Unit of CHCSJ or KW, to be properly investigated.

All cases should be reported as "AFP case" or "suspected acute poliomyelitis", using the official reporting form for Infectious Notifiable Diseases (UTVE-SSM-MOD.100, Modelo 1).

Step 2: Screening of cases with pediatrician assessment (hospitals)

Is the case clinically compatible with paralytic poliomyelitis or AFP, as defined previously?

If no: no further investigation or report is required.

If yes:

The case should be reported to UTVE (by fax) and immediately investigated (within 24-48 hours). The specific "AFP case investigation form" should be filled-up and line-listed as data becomes available (Cep1AFPform).

Two stool specimen (at least 8 grams each), should be collected 24-48 hours apart, but within 14 days after onset of paralysis or weakness, and submitted to the Virology Department of Queen Mary Hospital in Hong Kong (WHO-accredited laboratory), for virus isolation, typing and strain differentiation. The stool specimens should be send to Hong Kong by the staff of Public Health Laboratory, under the supervision of its director and in adequate transportation conditions (inside isothermal containers with ice or frozen icepacks); upon arrival there should be ice or frozen icepacks present inside the container, with no leakage or stool desiccation. The specific "AFP case laboratory request form" should be filled-up and send together with the samples (Cep3AFPform).

If possible, neurological investigations should be request, including nerve conduction studies and/or electromiography, and CT scan.

All cases should be reported as "AFP case" or "suspected acute poliomyelitis", using the official reporting form for Infectious Notifiable Diseases (UTVE-SSM-MOD.100, Modelo 1).

Step 3: Pediatrician assessment and/or expert review (hospitals)

Results of laboratory and neurological investigations outlined in step 2 should be evaluated, and follow-up arranged.

Step 4: Follow-up with pediatrician assessment (hospitals)

For all AFP cases (polio-compatible and non-polio AFP cases), a follow-up assessment of the outcome of paralysis/weakness, 60 days after its onset, should be performed by the CEP hospital coordinators.

The final diagnosis should be established and the "AFP case investigation form" completely filled-out and send to UTVE.

Management of close contacts

If wild poliovirus is isolated from a clinical specimen, the polio immunization status of close contacts of the case should be reviewed and their immunization updated, if needed.

Close contacts of a case are defined as:

household contacts – persons living in the same house or having close contact with the case (e.g., sharing sleeping arrangements or living in same house) within 30 days prior to the case's onset of illness,

day care attendees, or

persons having contact with stools or fecal matter of the case within 30 days prior to the case's onset of illness.

Reporting of incidental finding of wild poliovirus

The incidental finding of wild strain poliovirus in a clinical specimen, with or without clinical signs and symptoms of poliomyelitis, should be reported to UTVE and the Sanitary Authority, according to the procedures outlined before.

The polio immunization status of close contacts should be reviewed and their immunization updated, if needed (including all age groups).

Important data to report

The following information should be always sought and included in the report for each case.

Patient information:

- date of birth and gender,

- polio immunization status (total number of doses of injection/inactivated or oral/live polio vaccine received),

- receipt of oral polio vaccine (OPV) within 30 days prior to the onset of illness,

- travel history within 30 days prior to the onset of illness,

- summary of the clinical presentation, course of illness, and final clinical diagnosis,

- results of stool culture (and serological tests if available); if any of the required clinical specimens were not available for testing, this should be indicated in the report, and

- results of electromyography and/or nerve conduction studies, if available.

Information related to household contacts:

- receipt of OPV within 90 days prior to the onset of illness in the case, and

- travel history within 30 days prior to the onset of illness in the case.

© Fernando Costa Silva, 1999