Vaccine detonation polio threatens global eradication efforts July 10, 2018 Source: Chinese Journal of Science and Technology In rare cases, the weakened virus in the polio vaccine can restore toxicity and cause an outbreak. Image source: WHO In the shadow of the Ebola epidemic in the Democratic Republic of the Congo, another terrible virus is spreading: polio. Public health experts have been working hard to eradicate the virus for months, but it is still spreading. At present, it has paralyzed 29 children in the country. On June 21, there were reports of a case on the border with Uganda, which aggravated concerns that the virus would sweep across Africa. Michel Zaffran, head of the World Health Organization's Global Polio Eradication Initiative (GPEI), said the epidemic in the Democratic Republic of the Congo was “absolutely†the most worrying polio outbreak. The epidemic also highlighted new setbacks on the rugged road to eradicate polio. It is not caused by wild viruses that threaten Afghanistan, Pakistan, and Nigeria, but by a rare mutant derived from a deactivated oral polio vaccine (OPV). This mutation restores the neurotoxicity and ability of the attenuated virus. These vaccine-borne polioviruses (cVDPVs) have become the biggest threat to eradicate polio as OPV campaigns put wild viruses on the verge of extinction. Polio experts warn that if the epidemic does not stop quickly, it may lose control, thus eradicating eradication efforts for many years. Nicholas Grassly, an epidemiologist at Imperial College London in London, said that stopping these vaccine-initiated disease outbreaks is "imminent" and "this is much more important than controlling wild viruses." Safe and effective OPV has long been the main force in eradicating work. But a feature that makes the vaccine so powerful can also be a serious drawback. In a short period of time after vaccination, the weakened live virus will spread from person to person, even those who have not been vaccinated against polio can improve their immunity. But in rare cases, such as in poor countries where many children, such as the Democratic Republic of the Congo, have not yet been vaccinated, the virus can continue to spread for years and accumulate variations until it returns to dangerous forms. Currently, the vast majority of cVDPVs are caused by serotype II, and serotype II is one of the three variants of the virus. In 2000, when cVDPVs were discovered, the World Health Assembly in Geneva immediately announced that when wild viruses disappeared, all countries and regions must stop using OPV. In 2016, the threat of cVDPVs is growing – they now cause more cases of paralysis than wild viruses. GPEI believes that waiting is no longer an option. At that time, type II poliovirus was eradicated in the wild, which means that every type II virus now originates from the vaccine itself. In April of that year, 155 countries were still using the trivalent vaccine, which targets all three variants of the poliovirus. No one knows exactly how the eradication work will proceed. However, it is clear that in the next few years, some Type II polio outbreaks will still occur – either before the announcement of eradication but not discovered, or by those trivalent OPVs. In response to these outbreaks, the new unit price OPVII (mOPV2) inventory closely monitored by GPEI can only be issued after approval by the WHO Director General. Zaffran said that if you use mOPV2 wisely and cautiously, it can stop the outbreak of the epidemic without causing future outbreaks. Speed ​​is critical because the population's immunity to type II polio is weakening because it has been removed from the vaccine. The mOPV2 vaccine has been released in 10 countries to respond to outbreaks. Although Syria’s type II polio has paralyzed 74 children before it was brought under control last year, this strategy seems to be working so far. But the exception is the Democratic Republic of the Congo. The outbreak was first discovered in June 2017 in the province of Manima in the central part of the country. A few days later, an example was reported about 900 km from the Hout-Lomami province in the southeast. Genetic analysis revealed that it differed from the strains of Manima Province in that it appeared independently of type II cVDPV. To make matters worse, the sequence shows that the two viruses were not found for at least two years. The country and its international partners have targeted the mOPV2 campaign to eight health experts who are considered to be the most at risk, and believe that this can achieve maximum results at minimal cost. But in the Democratic Republic of the Congo, the promotion of vaccination campaigns is difficult due to remote villages, faltering infrastructure and weak health systems. The vaccination campaign did not reach enough children. The Hout-Lomami epidemic spread south to Tanganyika. Then, in the first week of June, officials confirmed another case on the other side of the country. It is not far from the Ebola epidemic area, and health workers are already stretched. This strain also appears independently. Even more worrisome is that, in about two weeks, a case of polio was reported in the northeast near the Uganda border. The virus has spread north, and there is no promotion of mOPV2 movement there. “This really increases the risk of international communication,†said Oliver Rosenbauer, spokesperson for the WHO polio eradication project. According to Mark Pallansch, a molecular virologist at the Centers for Disease Control and Prevention, in the worst case, if an outbreak occurs in Africa, or if the number of cases increases exponentially, the only option is to reintroduce OPV2 into routine immunization. As a result, the clock to eradicate work has been retrogressed, and the cost of about $1 billion a year has been rising, which has frustrated investors who have exhausted their funds. But Zaffran said that this scenario will take several years. Pallansch agreed. "At the moment, I believe that the Type II cVDPV is manageable. The only question is how long it will take. I have not seen anything that makes me think that eradication is impossible." (Tang Yichen compiled) Chinese Journal of Science (2018-07-10 3rd Edition International) Natural Plant Pigment,Plant Pigments,Natural Pigments,Plant Based Pigments Shaanxi Zhongyi Kangjian Biotechnology Co.,Ltd , https://www.zhongyibiology.com