Despite eradication of polio in Africa , global health officials remain vigilant
While Asia has been declared polio-free , isolated outbreaks still occur
After four years without a case of wild polio , Africa was declared polio-free in August , leading the World Health Organization ’ s director-general to declare the eradication effort to be “ one of the greatest public health achievements of our time ”.
“ With this historic milestone , five of the six WHO regions — representing over 90 percent of the world ’ s population — are now free of the wild poliovirus , moving the world closer to achieving global polio eradication ,” proclaimed Dr Tedros Adhanom Ghebreyesus on Africa ’ s new status . He singled out Africa ’ s strong public health leadership and coordinated efforts to immunise huge populations of children as factors for the success .
At present , only the WHO ’ s Eastern Mediterranean region , which includes Afghanistan and Pakistan where wild poliovirus is still endemic , has yet to eradicate the virus , which mainly affects children under five years of age .
The WHO defines polio as a highly infectious disease that invades the nervous system and can cause total paralysis in a matter of hours . The poliovirus is transmitted person-toperson , mainly through faecal-oral contact or by a common vehicle such as contaminated water or food from which it multiplies in the intestine .
Initial symptoms are fever , fatigue , headache , vomiting , stiffness of the neck , and pain in the limbs . One in 200 infections leads to irreversible paralysis , usually in the legs , and among those paralysed , 5-10 percent die when their breathing muscles become immobilised .
The WHO ’ s Western Pacific region , which is home to 37 countries and regions including China , the Philippines , and Malaysia , was certified wild-type polio-free in 2000 . Its Southeast Asia region , which includes India , Thailand , and Indonesia , followed suit in 2014 .
But this success does not mean poliovirus has been wiped off the face of the earth , according to Dr Jacqueline Lo Ring Yu , an infectious diseases specialist and WHO representative in Malaysia , Brunei and Singapore . As recently as 2019 , there were isolated outbreaks of the disease in the Philippines and Malaysia .
“ There are two types of polio viruses . One is the wild-type poliovirus , and when we declare a country as being polio-free , we are referring to the wild-type poliovirus , which is naturally occurring and circulates persistently in the community . With proper programmes we can eradicate it from a region ,” Dr Lo told Global Health Asia-Pacific .
There is also vaccine-derived poliovirus , which is much rarer but can lead to the same symptoms and be transmitted in the same way as wild poliovirus . Since oral polio vaccine contains a weakened vaccine-virus that replicates in the intestine for a limited period , the vaccine-virus will be excreted during this time . In areas of inadequate sanitation , it can spread within the immediate community before eventually dying out .
As a result , infections can occur in under-immunised populations and communities that lack proper sanitation and access to clean water . Such outbreaks have occurred in several Asian countries in recent years , including in Malaysia and the Philippines .
The WHO ’ s immunisation programme targets a region or country and sets out to immunise every child there within one or two weeks .
“ Both outbreaks of wild-type polioviruses or vaccinederived polioviruses underline the importance of having a good childhood immunisation programme that reaches every child , everywhere . We have had success with that , but there are always pockets occurring in some countries ,” said Dr Lo .
Disruption from this year ’ s coronavirus pandemic forced a pause in vaccination programmes for some months but resumed initially in the East Malaysian state of Sabah and have since been going well , said Dr Lo .
“ Covid-19 has caused a burden . It ’ s a challenge , and reports show that fewer people have been accessing basic health services , including immunisation programmes .
“ It ’ s a little early to say what the public health impact of this will be , but we ’ re working closely with the state health department in Sabah and the national immunisation programme , so it looks like the temporary interruption will not have an impact . But we ’ ll only know after we ’ ve finished evaluating ,” she added .
34 NOVEMBER 2020 GlobalHealthAsiaPacific . com