1. الرئيسية
  2. Southern Africa
  3. Angola

Tracking a poliovirus

Shelina Moonsamy isolates the wild polio virus which is used for sequencing at the NICD Jaspreet Kindra/IRIN
Like a Federal Bureau of Investigation agent, Nicksy Gumede-Moeletsi, a virologist who heads the sequencing section at the Polio Molecular Unit of South Africa's National Institute for Communicable Diseases (NICD), tracks her "criminal", in this case a virus, by studying variations in the "genotypes" instead of fingerprints.
 
The sequencing unit in South Africa is one of seven centres in the world that trace the origin of polio outbreaks. Gumede-Moeletsi traced the origins of the 2005 outbreak in Angola - which had remained polio-free since 2001 - to a polio strain prevalent in India by determining the genetic constitution of the poliovirus.

From Angola the Indian virus strain travelled south to neighbouring Namibia, north to the Democratic Republic of Congo (DRC) and from there reached the Central African Republic (CAR) in 2008.

Polio Facts
As long as a single child remains infected, children in all countries are at risk of contracting polio
Between 2003 and 2005, 25 previously polio-free countries were re-infected due to imports of the virus
One in 200 infections leads to irreversible paralysis (usually in the legs)

Among those paralysed, 5% to 10% die when their breathing muscles become immobilized

Source: WHO
Polio, a highly infectious non-curable disease that can cause total paralysis in a matter of hours, is spread quite easily by contact from person to person. The virus is also spread through faecal-oral contact, and there is evidence that flies can passively transfer poliovirus from faeces to food.

According to the Global Polio Eradication Initiative, spearheaded by the World Health Organisation (WHO), Rotary International, the US-based Centers for Disease Control (CDC) and UNICEF, most people infected with poliovirus have no signs of illness, and are never aware they have been infected.

The disease can be prevented by orally giving children aged under five a live weakened Sabin polio vaccine, named after Albert Sabin the scientist who developed the vaccine, or by a trained health worker injecting the inactivated Salk polio vaccine.

Uncovering the route along which a virus spreads is critical. Polio outbreaks can be caused either by a wild polio virus type, or a vaccine-derived poliovirus (VDPV).
On rare occasions, strains of the live virus contained in the oral polio vaccine (OPV) given to children are known to have changed, reverting to a form with the capacity to circulate, and which can cause paralysis in humans.

Gumede-Moeletsi said it was essential for a country experiencing an outbreak to know what it was up against, and sequencing helped detect the possibility of a new strain, as well as determining whether it was a wild polio virus or a VDPV.

Sequencing also helped to find gaps in the affected country's immunisation coverage. For example, if sequencing picked up a mutated form of the virus that seemed newer than a strain prevalent before the country's last vaccination drive, it might indicate that the coverage of the immunisation programme had not been that effective, said Dr Adrian Puren, deputy director of NICD.

Threat in Swat
The current military operation in Swat, Pakistan, which could displace up to a million people, is both an opportunity and a threat to the polio programme, according to the Global Polio Eradication Initiative. Swat has been inaccessible to immunisation teams since October, 2008. "The current displacement of the Swat population provides both an opportunity to reach under-immunised children and the possibility that these children could be carrying wild poliovirus out of inaccessible areas into crowded IDP camps".
Finish the job


The polio detective work has also been used to actively encourage Afghanistan, India, Pakistan and Nigeria - the only four countries which remain polio-endemic - "to finish the job of complete eradication", said Mark Pallansch, who heads the polio laboratory at the CDC. He has worked on the polio eradication programme since 1985 and has traced frequent outbreaks to a virus originating in the four countries.

In August 2003, radical Muslim leaders in three northern states of Nigeria suspended polio immunisation campaigns after rumours that the vaccine was laced with agents causing AIDS and sterility.

A new outbreak, originating in the state of Kano, subsequently occurred and infected previously polio-free areas of Nigeria as well as eight formerly polio-free countries in West and central Africa.

The strain then travelled from Sudan to Saudi Arabia, "probably during Haj", the annual Muslim pilgrimage to Mecca, Pallansch said, and in 2005 spread to Yemen as well as Indonesia – a country that had been polio-free for 10 years.

These outbreaks underline the importance of being vigilant. "You need a good surveillance system and a regular immunisation programme," said Pallansch. "As long as polio is endemic, even in one country, everyone has to keep up with their immunisation programme."

Nigeria's neighbour, Cameroon, had managed to keep the disease from developing into an outbreak with an effective immunisation campaign, he pointed out, unlike other neighbours, such as conflict-ridden Sudan.

Polio can be eradicated, "if you have the will," said Pallansch. "If a developing country like Bangladesh, with a huge population and challenges, can do it, anyone can do it." 

Gumede-Moeletsi is concerned about the threat posed by VDPV, which is mounting. In 2008 she picked up 18 cases in DRC and four in Ethiopia.

Her concern supports calls for wider use of IPV which eliminates the risk of VDPV as it does not contain live virus, once wild polio has been eradicated. However, according to Sona Bari of WHO, "only OPV has been proven to stop polio circulating within a community." So the debate on which vaccine to use continues.

jk/he

This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions

Share this article

Get the day’s top headlines in your inbox every morning

Starting at just $5 a month, you can become a member of The New Humanitarian and receive our premium newsletter, DAWNS Digest.

DAWNS Digest has been the trusted essential morning read for global aid and foreign policy professionals for more than 10 years.

Government, media, global governance organisations, NGOs, academics, and more subscribe to DAWNS to receive the day’s top global headlines of news and analysis in their inboxes every weekday morning.

It’s the perfect way to start your day.

Become a member of The New Humanitarian today and you’ll automatically be subscribed to DAWNS Digest – free of charge.

Become a member of The New Humanitarian

Support our journalism and become more involved in our community. Help us deliver informative, accessible, independent journalism that you can trust and provides accountability to the millions of people affected by crises worldwide.

Join