Major Polio Epidemic in Yemen, 22 infected : WHO

Twenty-two cases of Polio have been reported in Yemen, which had been polio-free for almost a decade. To control the outbreak, experts are planning a nationwide immunization campaign using a recently-developed vaccine which will specifically target this type of poliovirus.

Eighteen new cases of Polio have today been announced in Yemen, bringing the reported total number associated with an outbreak in the country to 22. Yemen had been polio-free since disease surveillance began in 1996.

A genetic investigation is ongoing to determine the precise origin of the outbreak. Experts fear that the number of cases will rise in the immediate future.

Teams of WHO and Ministry of Health epidemiologists and paediatricians remain on the ground, to investigate and control the outbreak and to intensify the planning for appropriate supplementary immunization activities.

“What we are facing now is a major epidemic of polio in Yemen,” said David Heymann, head of the WHO’s polio eradication program.

The WHO was awaiting genetic analysis of the virus to determine whether it had come from neighboring Saudi Arabia or Sudan, which have both registered cases in the past year.

“We’ll probably never be able to know whether the virus came from pilgrimage (to Mecca) or from guest workers… What is important is that the virus is there, and now we have to stop it,” Heymann said.

Yemen conducted a mass vaccination campaign in mid-April and further immunization rounds are planned in May and June.

Four cases of polio were confirmed on 20 April in just one governorate in the south-western part of the country, on the Red Sea coast. The latest 18 cases occurred across five governorates throughout Yemen, including in two districts in the country’s capital Sanaa and suggesting the virus had spread across the country. Ongoing field investigations have identified additional suspected polio cases across the affected governorates in Yemen. Low immunization rates among Yemen’s children may facilitate the spread of the virus.

A monovalent oral vaccine against type 1 polio, recently licensed by Sanofi-Pasteur, a unit of French drugmaker Sanofi-Aventisis, is being used in Yemen.

This new vaccine enables a precisely tailored immunological response to the type 1 poliovirus that is causing the outbreak. Compared to the commonly-used trivalent OPV, which offers protection against all three types of wild poliovirus, mOPV1 provides a greater immunity to type 1 wild poliovirus with fewer doses. Use of mOPV1 is expected during a nationwide immunization campaign in the second half of May. Yemen had already conducted a mass campaign on 11-14 April, as the country was considered to be at high-risk of polio re-infection from nearby Sudan where an outbreak of polio continues.

Experience in polio eradication demonstrates that outbreaks can be quickly contained with high quality immunization campaigns which reach every child under five years old.

Dedicated donor support and strong partnerships with the private sector have enabled the previous campaign in Yemen as well as swift development of the mOPV1 vaccine. However, a global funding gap of US$ 50 million must urgently be filled by July, to finance continued intensification of immunization campaigns in the second half of the year.

Global eradication efforts have reduced the number of polio cases from 350 000 annually in 1988 to 1267 cases in 2004. Six countries remain polio-endemic, with a further six where polio transmission is re-established. Concern is high that the ongoing outbreak of polio in Africa might lead to re-infection of more countries in the polio-free Horn of Africa and the Middle East. Yemen is the most recent of fifteen polio-free countries that have reported cases of polio since the epidemic began in late 2003.