Polio eradication falters
Polio has been stubbornly hanging on in parts of the world despite a global vaccination campaign, latest figures show.
The World Health Organisation originally aimed for the global eradication of polio by 2000, but although a massive reduction in clinical cases was achieved between 1988 when there were 350,000 and 1999 when there were 6,970, there has been a stubborn persistence since 2000 at about 400-1,950 cases globally each year.
Type 2 polio virus was eradicated in 1999 and type 3 is now confined to one small area of India, but type 1 persists in India, Pakistan, Afghanistan and Nigeria.
A major weapon in the mopping up operation for type 1 disease is the use of high potency monovalent type1 oral polio vaccine (OPV).
There are several reasons for the persistence of polio.
OPV does not work well in subjects with diarrhoea, and, of course, a high proportion of cases develop only flu-like illness. Paralytic polio affects 0.1 to 2% of infected persons, the tip of a very large iceberg of infection.
WHO has just reported a new outbreak of wild poliovirus type 1 in northern Nigeria, now at 272 cases since the start of the year, a ninefold increase compared to the same period in 2007.
From 2003-6 sustained polio transmission in Nigeria led to the re-infection of 20 previously polio-free countries, so there is considerable concern about the risk of renewed international spread from the current outbreak.
Adult travellers should continue to receive Revaxis, the combined polio, tetanus and diphtheria vaccine at 10-year intervals.