imm_afpsurv

Last modified at 24/08/2016 17:25 by hfwnhm

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ACUTE FLACCID PARALYSIS (AFP) SURVEILLANCE​

To achieve poliomyelitis eradication, the World Health Organization recommends that countries conduct surveillance for cases of acute flaccid paralysis. AFP is defined as a sudden onset of paralysis/weakness in any part of the body of a child less than 15 years of age. This syndromic reporting strategy, of investigation all AFP cases rather than just “suspected poliomyelitis”, serves many purposes. First, AFP surveillance substantially increases the sensitivity of the surveillance system and allows it to detect paralytic poliomyelitis due to wild poliovirus transmission in the population. Secondly, AFP surveillance provides objective data with which to monitor the quality of surveillance in an individual country or large population group. AFP Surveillance also helps to monitor progress in polio eradication when polio exists in a country as well as helps to define when polio is gone from the country or area.

BACKGROUNDThe global effort to eradicate polio has become the largest public health initiative in history and is spearheaded by the WHO. Polio is one of ony a limited number of diseases that can be eradicated. This is because polio only affects humans, an effective, inexpensive vaccine is available and immunity is life-long. There are no long term carriers of the disease, no animal or insect reservoir and the virus can only survive for a short time in the environment.

What is needed for AFP Surveillance?

  1. Stool samples (two samples, 24 hours apart, within two weeks of paralysis onset) should be sent to the NVRL for virological testing. 2. An enhanced surveillance form (available on HPSC website) be completed and sent to HPSC immediately and also a follow-up form 60dyas later(at follow ulp). Information collected includes clinical, vaccination and virological information.

SUMMARY: 

  1. Surveillance should be sensitive enough to detect at least one case of non-polio AFP for every 100,00 children under – 15 years of age. This parameter is used as a measure of the sensitivity of the surveillance system in operation in each country.
  2. At least two stool samples, taken 24 hours apart and within 14 days of the onset of illness should be collected from at least 80% of these cases. These stool samples should be sent to the NVRL under reverse cold chain conditions for appropriate virological investigation (for further details contract NVRL at 01 269 7611).
  3. Detailed investigation of suspected polio cases should include clinical, epidemiological and virological examination as well as a follow-up examination for residual paralysis after 60 days.
  4. All information relating to AFP cases will be reviewed by the National Polio Elimination Committee.

There are many causes of AFP, so each AFP needs to be evaluated to find out if the paralysis is due to polio or not. Polio is only one out of the many causes of AFP.
The surveillance system for polio is being maintained in India even after polio-free certification has happened to demonstrate that there is no polio in India and to pick up any importation of poliovirus, if they occurred. 
There are globally recommended indicators of quality for the AFP surveillance system. One of the indicators is the rate at which a country detects and investigates AFP cases. If a country detects AFP cases below this rate, the surveillance system in that country is considered not sensitive enough to detect polio. India has not only been achieving these indicators of surveillance quality but has been surpassing them over the past many years.