Citation style for this article: Anis E, Kopel E, Singer SR, Kaliner E, Moerman L, Moran-Gilad J, Sofer D, Manor Y, Shulman LM, Mendelson E, Gdalevich M, Lev B, Gamzu R, Grotto I. Insidious reintroduction of wild poliovirus into Israel, 2013. Euro Surveill. 2013;18(38):pii=20586.
Abstract and background below; full text, with tables, is online at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20586
Date of submission: 09 September 2013
Israel was certified as polio-free country in June 2002, along with the rest of the World Health Organization European Region. Some 11 years later, wild-type polio virus 1 (WPV1) was isolated initially from routine sewage samples collected between 7 and 13 April 2013 in two cities in the Southern district. WPV1-specific analysis of samples indicated WPV1 introduction into that area in early February 2013. National supplementary immunisation with oral polio vaccine has been ongoing since August 2013.
Detection of wild poliovirus in Israel
Wild poliovirus type 1 (WPV1) was isolated from routine samples collected during epidemiological week 15 (7 to 13 April 2013) in sewage treatment facilities in Beer Sheva and Rahat, two cities in Israel’s Southern district. Beer Sheva, the regional commercial centre, has a population of about 200,000. It is situated 20 km south of Rahat and there is considerable population movement and commerce between the two cities.
Poliomyelitis (polio) has been a notifiable disease in Israel since 1951. WPV1 predominated during the large, pre-vaccine national epidemics during 1949 to 1956 [1,2] with a peak incidence of 129.4 cases per 100,000 of the general (mostly Jewish) population in 1950 . Substantial control of polio was achieved by the mid-1960s (0.1 per 100,000 in 1965) through universal childhood vaccination with trivalent oral polio vaccine (OPV), followed by low-level activity throughout the 1970s (0.2-0.9 per 100,000), particularly in the Jewish population (0.1 per 100,000 Jewish population). Annual campaigns with type 1 monovalent OPV further reduced polio incidence also among the non-Jewish population in the 1980s (0.1 to 0.3 per 100,000 non-Jewish population) .
Israel has not had a polio case since an outbreak in 1988, in which 15 poliovirus-infected people had paralytic polio, mostly in the Hadera sub-district in the northern part of the country [1,3], following importation of WPV1 from northern Egypt the year before the outbreak [1,4]. Most of the 1988 outbreak cases had received OPV in the past. A mass trivalent OPV vaccination campaign ended the outbreak .
In 1990, a routine national vaccine programme – combining three inactivated polio vaccine (IPV) doses with three trivalent OPV doses – was implemented. This schedule continued until 2005, when OPV was discontinued three years after the polio-free status certification by the World Health Organization (WHO), in June 2002 . The IPV-only schedule since 2005 prescribes three IPV doses by the age of six months with two additional booster doses at 12 months and at seven years (second elementary grade) (Table 1). The 2012 national IPV3 coverage was 95% .
Israel has maintained a routine environmental polio surveillance programme since 1988, through monthly sampling of eight to 10 sewage treatment facilities in largely populated areas or areas considered sentinels of risk for importation of WPV, such as Rahat, a major Bedouin city, which was the initial importation locus of the 1988 WPV1 outbreak . Additionally, since 1996, notification of cases with acute flaccid paralysis (AFP) up to the age of 15 years has been mandated by law and active AFP surveillance has been implemented. Since then, the level of reporting fluctuated, sometimes below the WHO threshold (1 case of AFP per 100,000 population <15 years of age). As a consequence, the structure of the active AFP surveillance system was reorganised several times in the past years, and since January 2013, the national Division of Epidemiology contact directly, on a weekly basis, each representative of the relevant clinical care units in the country, in order to obtain the complete information on any suspected AFP cases, and assuring the required clinical sampling for the necessary laboratory tests.
Here we describe the epidemiology of the reintroduction of WPV1 into Israel in 2013, a potential public health emergency at the national level and public health threat at the global level.
21 September 2013 – WHO considers the risk of further international spread of wild poliovirus type 1 (WPV1) from Israel to be high. The risk assessment reflects evidence of increasing geographic extent of WPV1 circulation in Israel over a prolonged period of time. Recently, WPV1 has also been isolated from sewage samples collected by the Palestinian Authority , both in West Bank and the Gaza Strip. No cases of paralytic polio have been reported by Israel or the Palestinian Authority.
Health authorities of Israel and the Palestinian Authority have taken steps to respond to the threat posed by WPV1 circulation by strengthening surveillance for acute flaccid paralysis and increasing the frequency of environmental sample collection. A supplementary immunization activity with bivalent oral polio vaccine (bOPV) is being conducted in Israel since early August, targeting children up to nine years of age to rapidly interrupt WPV1 circulation. As of now, 60 percent of the 1.38 million children targeted in Israel have been vaccinated. Health authorities of the Palestinian Authority are preparing to conduct two supplementary immunization activities with trivalent OPV in the Gaza Strip and in West Bank.
It is important that all polio-free countries, in particular those with frequent travel and contacts with poliovirus-affected countries and areas, strengthen surveillance for cases of acute flaccid paralysis in order to rapidly detect any new virus importations and to facilitate a rapid response. Countries, territories and areas should also maintain uniformly high routine immunization coverage at the district level to minimize the consequences of any new virus introduction.
WHO’s ‘International Travel and Health’ recommends that all travellers to and from poliovirus-affected countries and areas be fully vaccinated against polio. Three countries remain endemic for indigenous transmission of wild poliovirus virus: Afghanistan, Nigeria and Pakistan. Additionally, in 2013, the Horn of Africa has been affected by an outbreak of wild poliovirus type 1.