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Environmental surveillance system to track wild poliovirus transmission
Jagadish M Deshpande1, Sushmitha J Shetty, Zaeem A Siddiqui
1Enterovirus Research Centre, Haffkine Institute Compound, A. Donde Marg, Parel, Mumbai, India 400 012. erc@bom3.vsnl.net.in
Abstract:
Eradication of poliomyelitis from large metropolis cities in India has been difficult due to high population density and the presence of large urban slums. Three paralytic poliomyelitis cases were reported in Mumbai, India, in 1999 and 2000 in spite of high immunization coverage and good-quality supplementary immunization activities. We therefore established a systematic environmental surveillance study by weekly screening of sewage samples from three high-risk slum areas to detect the silent transmission of wild poliovirus. In 2001, from among the 137 sewage samples tested, wild poliovirus type 1 was isolated from 35 and wild poliovirus type 3 was isolated from 1. Acute flaccid paralysis (AFP) surveillance indicated one case of paralytic poliomyelitis from the city. Phylogenetic analysis with complete VP1 sequences revealed that the isolates from environmental samples belonged to four lineages of wild polioviruses recently isolated from poliomyelitis cases in Uttar Pradesh and not to those previously isolated from AFP cases in Mumbai. Wild poliovirus thus introduced caused one case of paralytic poliomyelitis. The virus was detected in environmental samples 3 months before. It was found that wild polioviruses introduced several times during the year circulated in Mumbai for a limited period before being eliminated. Environmental surveillance was found to be sensitive for the detection of wild poliovirus silent transmission. Nucleotide sequence analysis helped identify wild poliovirus reservoir areas.
Insights
Environmental surveillance detected wild poliovirus (WPV) silent transmission in Mumbai, India. Sewage screening identified WPV in high-risk areas, aiding in understanding its circulation and origins.
Area of Science:
- Public Health
- Virology
- Epidemiology
Background:
- Eradicating poliomyelitis in densely populated Indian cities with urban slums is challenging.
- Despite high immunization rates, paralytic poliomyelitis cases occurred in Mumbai in 1999-2000.
Purpose of the Study:
- To establish systematic environmental surveillance for detecting silent wild poliovirus transmission in Mumbai.
- To identify the origins and circulation patterns of wild poliovirus in urban environments.
Main Methods:
- Weekly screening of sewage samples from three high-risk slum areas.
- Isolation and phylogenetic analysis of wild poliovirus using complete VP1 sequences.
- Correlation with Acute Flaccid Paralysis (AFP) surveillance data.
Main Results:
- Wild poliovirus type 1 and type 3 were isolated from 36 out of 137 sewage samples in 2001.
- Environmental isolates belonged to lineages recently found in Uttar Pradesh, not previous Mumbai cases.
- Wild poliovirus was detected in sewage 3 months prior to the single reported AFP case.
Conclusions:
- Environmental surveillance is a sensitive tool for detecting silent wild poliovirus transmission.
- Phylogenetic analysis helps identify wild poliovirus reservoir areas and introduction sources.
- Multiple introductions and limited circulation of wild poliovirus occurred in Mumbai before elimination.