Surveillance of acute flaccid paralysis

Learn how AFP is monitored.

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What is acute flaccid paralysis

Acute flaccid paralysis (AFP) is defined as the sudden onset of muscle weakness or paralysis. In Canada, we conduct surveillance of AFP in children less than 15 years old. The muscle weakness is characterized as flaccid, meaning that there is reduced tone in the muscle, and there is no other obvious cause (e.g., trauma) for the condition. Transient weakness (weakness that lasts for a short period of time), should not be considered when diagnosing AFP.

There are several causes of flaccid paralysis, including conditions such as viral or bacterial infections, autoimmune disorders, exposure to environmental toxins and Guillain-BarrĂ© Syndrome. Once a case of flaccid paralysis or muscle weakness is suspected, additional investigations are needed to determine the underlying cause. Sometimes no cause can be found.  Acute flaccid myelitis (AFM) refers to a subtype of AFP where specific changes to the spinal cord can be seen on magnetic resonance imaging (MRI).

How Canada monitors cases of acute flaccid paralysis

Surveillance of acute flaccid paralysis (AFP) in Canada is a collaborative effort between the Public Health Agency of Canada and the Canadian Paediatric Society, through the Canadian Acute Flaccid Paralysis Surveillance System (CAFPSS). The surveillance system monitors for all forms of AFP.

As AFP is a characteristic of polio, the purpose of national AFP surveillance is to ensure prompt, appropriate investigation of AFP cases to rule out the possibility of poliovirus infection. Canada was declared polio-free in 1994 however, active monitoring for possible cases is crucial to ensuring the safety of all Canadians.

All reported AFP cases are reviewed to determine compatibility with national surveillance definitions for paralytic poliomyelitis. The information provided by health care providers treating patients with suspected AFP is essential for making this determination.

CAFPSS began in 1991 through the Canadian Immunization Program Monitoring Active (IMPACT) network of paediatric hospitals, and in 1996 was expanded to include data collection from a network of over 2 700 paediatricians across Canada.

Acute flaccid paralysis in Canada

Since 2014 annual cases of AFP in Canada have ranged from 27-51.

Since 2014, of all the AFP cases identified in Canada, approximately half were diagnosed with Guillain-Barré syndrome and approximately 20% with transverse myelitis.

Figure 1. Number of confirmed AFP cases in Canada, by year, 1996 to 2017

Figure 1 - Long description
Year Number of AFP cases
1996 27
1997 35
1998 43
1999 60
2000 63
2001 53
2002 44
2003 44
2004 38
2005 54
2006 38
2007 50
2008 43
2009 58
2010 47
2011 44
2012 33
2013 36
2014 51
2015 27
2016 46
2017 27

Cases of acute flaccid paralysis around the world

AFP remains a rare, but serious condition. More than 150 countries have reported cases of non-polio AFP to the World Health Organization in 2017. For the same year, over 100 000 cases have been reported worldwide in children less than 15 years of age for an annual rate of approximately five cases per 100 000 population.

In the Region of the Americas, 22 countries conduct AFP surveillance. In 2017, the rate of AFP in the Americas was about one case per 100 000 population in children less than 15 years old.

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