Hello everybody. I'm Stephan Zientara, I am a doctor in vet medicine. I am the head of a Joint Research Unit in Virology. This is a research unit between three institutes: ANSES, which is a National Agency for Food Safety, INRAE, which is a National Institute for Agronomic Research on Environment. And the Veterinary School of Maisons-Alfort and my lab is based in the veterinary school in Maisons-Alfort near Paris. In my unit we work on viral diseases which infect only animals or on zoonotic viruses which infect animal and human. Today, my talk will be about West Nile, an example of a one health approach. And West Nile is a virus which caused the West Nile disease, a flavivirus, which infect animal and humans and transmitted by mosquitoes, so an arbovirus. The scientific literature estimates that approximately 60 percent of all human pathogens are zoonotic and that 75 percent of all recently emerging infectious diseases affecting humans have animal origin, most frequently wildlife, and you can find all this information in a paper published in Nature in 2008 by Jones and colleagues. You'll know that our world is changing very fast and I will not develop this point. You all know that, in particular is the international trade and travel has increased a lot, and SARS-CoV-2 is a very good examples that a virus which emerged somewhere in the world can be spread in all of the globe. Another important element is a global warming. You know that the temperature of our globe is increasing, and in particular from diseases transmitted by insects.This has major impacts. If you go to PubMed, which is a database of many scientific literature, you can see that the number of research papers related to climate change and diseases in animals and humans field has increased since 2005, and a lot of research team are working on this important event. Coming back to West Nile, West Nile is a virus from the Flaviviridae family, a flavivirus. This virus is transmitted from bird to bird by mosquitoes. This mosquitoes from time to time can bite as the hosts and birds. Many mammals can be bitten by mosquitoes and can be infected by mosquitoes if they're infected. The mosquitoes are biological vectors, means that they replicate the virus. Viruses are present in the salivary gland and when the mosquito bite the host it neutralize the virus at the same time. You have many hosts which can be infected by this virus. Horses, humans, but other, many many other species. All species are then end host, so as they are not responsible of another cycle. The cycle aborts when they're infected. It has also been shown that amongst the population of birds, the virus can be also transmitted directly from bird to birds, but this is a rare event and in human medicine, cases of West Nile, have been reported following transfusion of blood or graphs of kidneys, corneas, of livers, of hearts, so this is a major issue in terms of public health. Concerning the clinical signs in humans but also in animals, and particularly in horses which have a very similar clinical patterns, and in humans, in the majority of cases, about 80 percent of cases you have asymptomatic forms, no clinical signs. In 20 percent of the cases, you can have a flu syndrome or psuedo-flu and in 1-10 percent, it depends, you can have neurological signs or meningoencephalitis, encephalitis, which can sometimes cause deaths of people infected with West Nile or a horse infected with West Nile virus. So, this virus was first identified in 1937 in Uganda, at that time there was an epidemic of yellow fever and this virus is very similar to a yellow fever but it's different and it was named West Nile virus because it was on the West coast of the Nile river. Between 1947 and 1999, some cases were described in literature, but it was really in 1999 that West Nile became a major problem in human health. Why? because this virus was introduced in the American continent. The American continent was free of this virus and this virus spread from Canada to all countries in America. If you look to the number of cases in the USA, there was 62 cases in 99 with seven deaths in human population. The number have increased, and every year you have a lot of cases of West Nile or deaths. For example, in 2021, more than 1850 neuro invasive cases of West Nile have been reported, with 191 deaths. Between '99 and 2010, more than 1.8 million infections have been reported in humans. This is a paper published by Kilpatrick and colleagues in Science in 2011. More precisely, in the US between 1999 and 2019, it's more than 51,000 cases of West Nile which have been reported by CDC's ArboNET, which is a network organized by the CDC to manage arborviral diseases. It was estimated that more than 3.5 million infections in the US have been reported in a paper published in PLOS Neglected Tropical Diseases. The total cost of West Nile from 1999 to 2017 in the US was estimated to 778 million US dollars. Annually, this equates to US 56 million lost to West Nile virus. This is a paper published by Staples et al. in 2014. In Europe, West Nile virus circulates from different lineages like western virus according to the genetic sequences. In Europe, we have Lineage 1 and Lineage 2. Lineage 1, which emerged in 1998, and Lineage 2 in 2004. These two virus since circulate, and for example, in 2021, more than 130 human cases of West Nile had been reported in different countries of the European Union, and also 37 outbreaks have been reported in horses in EU. Every year we have cases reported in humans, in horses and in birds. There are some differences between Europe and America. In North America in particular, there were a single introduction of the virus, There was a very rapid expansion of the virus from the US to Canada, to Central America, and South America. You have many outbreaks, many human and veterinary cases and birds were largely affected. Which is not the case in Europe where you have multiple introduction, which are more or less sporadic, self-limited outbreaks, and there are few birds infected. As it says, differences that raise some question about these differences between America and Europe. Source of vector of West Nile is mosquitoes, and more than 75 species of mosquitoes have been shown to be able to transmit West Nile virus, but skewed X is the main vector. Birds can die, and in particular crows and blue jays in the US, are very sensitive to West Nile infection. Population of birds have been really affected by this infection, and this has been published by LaDeau et al. in nature in 2007. It's very difficult to predict the introduction of West Nile in Europe, and there is a surveillance system put in place, for example, in the EU, West Nile virus is notifiable disease in humans and equids in European Union. You have a bird surveillance which have been put in place and the cases are reported by European CDC since 2020, in Avifauna. You have also equine surveillance process spreads put in place and the cases are reported by ECDC since 2017, and of course also there is a human surveillance system and the cases are reported by ECDC since 2010. You will see that you have the three elements, surveillance in birds, surveillance in horses, surveillance in humans, which are of course linked. And there are different systems put in place in European Union: active surveillance, passive surveillance or in some countries no surveillance at all. So, my key message was that management under the surveillance of an emerging arbovirus disease like West Nile is based on the three pillar, human health, animal health, and environment. The management needs to have these three components working together, and this is absolutely fundamental. This is the basis of this One Health approach. Thank you very much to all.