CHAPTER ONE

INTRODUCTION

1.1       Background of the Study

Poliomyelitis, is an infectious disease caused by poliovirus, a member of the

genus Enterovirus. There are three serotypes of poliovirus: that is, 1, 2 and 3, these

three serotypes are mainly different in their virulence. The serotype 1 is the most

virulent of the three types, while serotype 2 and 3 are more sporadic (National Primary

Health Care Development Agency, 2015). Human cells contain specific protein

receptors to which poliovirus may attach and thereby enter susceptible cells. The virus

infects cells of the oropharynx, the tonsils, the lymph nodes of the neck, and the small

intestines. Infection progresses through cycles of virus replication, resulting in

destruction of the infected cells. Once infection is established, poliovirus can enter the

bloodstream and invade the central nervous system through the blood/brain barrier, by

spreading along nerve fibers, or by both routes (WHO, 1999). When non-immune

persons are exposed to wild poliovirus (Wild Polio Virus is caused naturally and not

caused by vaccine containing live virus) the results may include inapparent infection

without symptoms, mild illness, aseptic meningitis, or paralytic poliomyelitis

The Poliovirus can be spread to others by droplets from the upper respiratory tract

during the early days of infection. More commonly, infected persons pass large

numbers of virus particles through their faeces, from where they may be spread

indirectly, or directly to infect others .

Poliomyelitis is a serious public health problem. It has persisted in a few

countries from where it has spread to a large number of countries and posed threat to

health as it did earlier between the 1950‟s and 1980‟s. In the developing world, the

disease presents a constant threat to underfives, resulting paralysis with devastating

15

consequences for social and economic development (Lucas and Gilles, 1990).

Poliomyelitis is a highly infectious disease caused by a virus that mainly affects

children under the age of 5 years. The disease is transmitted through fecal oral route to

invade the nervous system and cause death or total paralysis in a matter of hours for

those who survive (WHO, 2003). According to Debras, Stephanie, Penny and Mia

(2005), Poliomyelitis is known to be one of the major causes of physical disability

worldwide, hence the need for its eradication. Viewed globally, vaccines are the most

cost-effective medical intervention to prevent death occurences and disease related to

poliomyelitis (World Bank, 1990). Therefore, immunization is the gateway to health

care for all children who are at the risk of this disease. The disease is of great public

health concern worldwide especially among young children under 5 years of age.

The set date by WHO for polio eradication globally was the year 2000.

However, this target was not achieved as about 3,500 cases of Wild Poliovirus were

reported worldwide in 2001 with Nigeria contributing 27 cases (WHO Nigeria, 2001).

Wild poliovirus is only endemic in six countries – Nigeria, India, Pakistan, Niger,

Afghanistan and Egypt. Five States within Nigeria, India and Pakistan account for more

than 75 percent of all new cases of polio worldwide and thus constitute the targets for

the global eradication of the disease. The world‟s few remaining reservoirs of the

poliovirus continue to pose significant risks due to the migration-imported polio virus,

which can spread rapidly and threaten unprotected children (WHO, 2004).

It is in response to this threat of rapid spread that the WHO in 1974 set up a special

programme known as the Expanded Programme on Immunization (EPI) which was

adopted in Nigeria as Federal Ministry of Health policy code named National

Programme on Immunization (NPI) on 1st September, 1985. Its major objective was to

immunize all the children and particularly those under one year old against the six killer

16

diseases which the WHO, United Nations Children‟s Fund (UNICEF) and various