2024-10-27 22:00:00
What do we know about the situation in Guyana?
As part of a research project coordinated by the ANRS-MIE, polioviruses derived from the Sabin type 3 vaccine strain (PVDV 3), presenting a similar genetic profile, were detected in wastewater samples collected between May and August 2024 in several wastewater treatment plants in Guyana (Cayenne, Saint-Georges and Remire-Montjoly).
Genetic analyzes of these samples carried out by the National Reference Center for Enteroviruses and Parechoviruses (Institut Pasteur Paris) show that the viruses present sufficient mutations (more than 10), compared to the strain contained in the oral vaccine, to consider it as a strain derived from the Sabin 3 vaccine strain (PVDV 3), and that they are genetically related to each other. These genetic analyzes also indicate that these strains should be considered wild poliovirus strains since they could cause paralysis.
These strains have not yet been identified in other countries. In Guyana, although no case of poliomyelitis has been reported so far, the detection of these strains from samples coming from different locations at least two months apart, confirms human-to-human transmission, without prejudging of its exclusive nature to Guyana, and the classification as circulating poliovirus cPVDV3 according to the World Health Organization.
Public Health France is taking stock of the risks of contracting poliomyelitis for the population and is strengthening its surveillance system in conjunction with ARS Guyana and its partners.
Why are polioviruses detected in wastewater?
When infected with poliovirus, the virus multiplies in the intestine and is excreted through the stool of an infected person. The viral particles present in the stool are then found in wastewater. As most poliovirus infections are asymptomatic, wastewater monitoring can detect virus circulation even before a case of paralysis occurs.
In France, this surveillance was operational from 1973 to 2018 on 4 wastewater treatment stations in Ile-de-France, but it was stopped at the end of 2018 due to low detection of poliovirus and high vaccination coverage. .
This is the first detection of VDPV circulating in a region in France since the 2000s. These detections demonstrate a silent circulation of VDPV3 within a Guyanese population with insufficiently vaccinated population groups.
What is the origin of these viruses?
As the oral vaccine is not used in Guyana, these viruses derived from vaccine strains were imported by one or more people who had received the oral vaccine abroad, and transmission from one individual to another may have been facilitated. among insufficiently vaccinated population groups. Note that the oral polio vaccine (OPV) is still used in certain South American countries.
Although the Americas region has been considered free from poliovirus circulation since 1984 by the WHO, this detection has consequences at the international level. Thus, the World Health Organization (PAHO) has since reminded all countries in the America region of the importance of strengthening surveillance of flaccid paralysis in children but also in adults, and of achieving high vaccination coverage (95% at 3 doses). Furthermore, the ECDC approved WHO’s temporary recommendations for EU/EEA citizens who reside in or are long-term visitors (>4 weeks) to Guyana: an additional dose of poliovirus vaccine must be administered between four weeks and 12 months before international travel. Travelers to Guyana must be vaccinated in accordance with their national schedules.
What is the risk for the Guyanese population?
Whatever the geographical origin of these viruses, the currently clinically silent circulation of PVDV3 in the Cayenne metropolitan area and in Saint Georges is associated with a low risk of paralytic forms (8 out of 10,000 people infected for viruses of the type 3, variable according to age; lower risk than for type 1 viruses for which it is estimated at 1 in 200) to develop poliomyelitis in people who are not or insufficiently vaccinated, in particular children and infants and immunocompromised people.
The risk of developing severe neurological forms, however, is extremely low for people who are up to date with their vaccination.
In Guyana, despite a diversified vaccination offer through several actors (liberal sector, PMI Centers, Delocalized Prevention and Care Centers, local hospitals or even associations) vaccination coverage is lower than that of mainland France, with population groups insufficiently vaccinated, particularly in isolated areas. Insufficient vaccination coverage, associated with precarious or promiscuous living conditions (community living) favoring essentially fecal-oral transmission of the virus by direct contamination (dirty hands or contaminated objects) or via a soiled environment ( wastewater, food) or even direct respiratory transmission, increases the risk of developing poliomyelitis as well as human-to-human transmission of poliovirus.
What are the recommendations and measures put in place by the health authorities?
Faced with the situation, several actions are being implemented by the health authorities in collaboration with health professionals:
Launch of a catch-up vaccination campaign: In schools by the ARS to vaccinate children and adolescents who are not vaccinated or not up to date with their vaccinations for all compulsory vaccinations in the schools of Cayenne, Rémire-Montjoly, Matoury and St-Georges de l’Oyapock.Outside the school environment to vaccinate in particular infants and children not admitted to communities and who are not up to date with their vaccination, always in the geographical area concerned by this detection.All health professionals in Guyana authorized to vaccinate are also invited to check the vaccination status of their patients throughout the territory, in particular children and immunocompromised people, and to carry out catch-up vaccinations if necessary. Raising awareness of health professionals about the risk of occurrence of cases of poliomyelitis with a reminder of the action to be taken in the face of any suspicion of poliomyelitis and in particular the taking of samples suitable for research of the genome by PCR and/or culture (2 stools taken 24 hours apart) by the CNR of enteroviruses and parechovirus and looking for differential diagnoses (nasopharyngeal sample, blood) by the CNR or any other medical biology laboratory. Establishment of a one-year environmental monitoring program on wastewater: the Pasteur Institute of Guyana , which is already responsible for the physicochemical monitoring of wastewater, will also search for the poliomyelitis virus during this period in collaboration with the CNR for enteroviruses Institut Pasteur Paris, also a WHO collaborative center. This study, planned for one year, should make it possible to define the extent and evolution of the circulation of poliovirus in wastewater, and to draw conclusions in terms of health management. It will make it possible to verify whether the measures put in place make it possible to stop the circulation of these strains of poliovirus in Guyana, and to decide on possible other actions to be implemented.
In addition, it is recalled that the risk of contamination can be reduced by applying standard hygiene measures (washing hands with soap before preparing meals, before eating and after going to the toilet and by washing and peeling fruits and vegetables before eating them).
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#Circulation #poliovirus #wastewater #Guyana
**Interview with Dr. Emily Hart, Public Health Expert on Poliovirus Situation in Guyana**
*Interviewer:* Thank you for joining us today, Dr. Hart. There’s been alarming news regarding the detection of polioviruses in wastewater samples from Guyana. Could you explain to our audience what this discovery entails?
*Dr. Hart:* Certainly, and thank you for having me. The detection of polioviruses derived from the Sabin type 3 vaccine strain in wastewater samples from various locations in Guyana is concerning. These samples, collected between May and August 2024, show genetic mutations indicating potential human-to-human transmission. While no reported cases of poliomyelitis exist yet, the presence of these strains suggests a public health risk that requires attention.
*Interviewer:* Why are we seeing the detection of these polioviruses specifically in wastewater?
*Dr. Hart:* Polioviruses are shed in the stool of infected individuals and enter the wastewater system, making wastewater monitoring an effective surveillance tool. Many infections are asymptomatic, meaning individuals can carry and transmit the virus without knowing they are infected. Monitoring wastewater can provide early indications of viral circulation before any clinical cases arise.
*Interviewer:* What can we infer about the origin of these viruses in Guyana?
*Dr. Hart:* The inference is that these vaccine-derived poliovirus strains were likely imported by individuals who received the oral polio vaccine in other countries. This highlights a critical gap in vaccination coverage in certain populations within Guyana. The outbreak underscores the need for vigilant monitoring and vaccination strategies, especially in areas with historically lower immunization rates.
*Interviewer:* What actions are being taken to address this situation in Guyana?
*Dr. Hart:* Public health authorities are taking proactive measures, including launching catch-up vaccination campaigns. These campaigns aim to vaccinate children and adolescents who are unvaccinated or not up to date with their vaccinations in regions like Cayenne and Saint-Georges. There is also a push for health professionals to ensure that vaccinations are being administered to all eligible populations, particularly in isolated or underserved areas.
*Interviewer:* what is the potential risk for the Guyanese population moving forward?
*Dr. Hart:* For unvaccinated or insufficiently vaccinated individuals, especially young children and immunocompromised persons, the risk of developing poliomyelitis is elevated, although the overall risk is still considered low based on current data. However, for vaccinated individuals, the likelihood of severe illness remains extremely low. The focus now must be on increasing vaccination coverage to protect vulnerable communities and prevent further transmission.
*Interviewer:* Thank you, Dr. Hart, for shedding light on this important public health issue.
*Dr. Hart:* My pleasure, and thank you for raising awareness about the situation in Guyana. It’s crucial for everyone to stay informed and prioritize vaccination to prevent the re-emergence of this disease.
