WEBVTT - Ep 164 Rift Valley Fever: Ruminating on ruminants 0:00:00.520 --> 0:00:04.400 A pathologist RS, aged thirty years, had been working with 0:00:04.480 --> 0:00:07.520 rift Valley fever virus for several weeks before the onset 0:00:07.560 --> 0:00:10.880 of his illness. On the evening of December twenty second, 0:00:10.960 --> 0:00:14.120 nineteen thirty two, he felt chilly while walking home and 0:00:14.200 --> 0:00:16.720 complained that his eyes and the calves of his legs 0:00:16.760 --> 0:00:20.439 ached during the night. His rest was disturbed by general 0:00:20.480 --> 0:00:24.560 malaise and pains, especially around the knees and hips. On 0:00:24.640 --> 0:00:27.920 awakening the second day of illness, his temperature was one 0:00:28.000 --> 0:00:31.520 oh one fahrenheit. He attempted to continue his work, but 0:00:31.600 --> 0:00:34.400 had several chills during the day and felt so miserable 0:00:34.440 --> 0:00:37.080 that he took to bed. He complained at this time 0:00:37.159 --> 0:00:40.920 of a vague soreness over his abdmen, constant dull headache, 0:00:41.200 --> 0:00:45.440 and pain behind the eyes associated with slight photophobia. There 0:00:45.479 --> 0:00:49.600 was no sore throat, rhinitis, nausea, or vomiting. He was 0:00:49.600 --> 0:00:52.680 admitted to the hospital of the Rockefeller Institute twenty four 0:00:52.680 --> 0:00:56.840 hours after the onset of symptoms. On admission, the temperature 0:00:56.880 --> 0:01:02.000 was one o two point six fahrenheit pulse respirations twenty four. 0:01:02.600 --> 0:01:06.320 The patient was definitely prostrated by his illness, but rational 0:01:06.400 --> 0:01:10.600 and cooperative. The throat culture was negative for hemolytics streptococcie 0:01:10.720 --> 0:01:15.840 and influenza bacille, and blood cultures in infusion broth remained sterile. 0:01:16.480 --> 0:01:20.000 A tentative diagnosis of riffelly fever or influenza was made. 0:01:20.360 --> 0:01:23.760 In an attempt to confirm the tentative diagnosis of riffelly fever, 0:01:24.319 --> 0:01:27.119 six ce seeds of the patient's blood was injected into 0:01:27.160 --> 0:01:30.759 six mice. All of the mice died within forty eight hours. 0:01:31.120 --> 0:01:35.440 Almost immediately after admission, the patient began to improve. The temperature, 0:01:35.480 --> 0:01:37.800 which reached a peak of one oh three point eight 0:01:37.840 --> 0:01:41.000 fahrenheit on the night of admission, fell promptly to normal 0:01:41.040 --> 0:01:45.480 within twenty four hours. The symptoms, however, abated somewhat less rapidly. 0:01:46.040 --> 0:01:48.480 By the twelfth day of illness, the patient had improved 0:01:48.520 --> 0:01:50.720 to such an extent that he was allowed to sit 0:01:50.760 --> 0:01:52.880 in a chair for a short time, and on the 0:01:52.920 --> 0:01:56.160 following day was permitted to walk a short distance. On 0:01:56.240 --> 0:01:59.280 the evening of the sixteenth day, however, he complained of 0:01:59.320 --> 0:02:02.280 pain in the life left leg. The patient was returned 0:02:02.280 --> 0:02:05.280 to bed and the leg was immobilized in an elevated position. 0:02:06.040 --> 0:02:09.440 Four days later, twentieth day of illness, the patient awakened 0:02:09.440 --> 0:02:11.960 with pain in the right chest, which was more pronounced 0:02:12.040 --> 0:02:16.360 during deep inspiration or exhalation. In the X ray photograph 0:02:16.360 --> 0:02:18.960 made at this time, there was a distinct shadow at 0:02:18.960 --> 0:02:22.480 the base of the right lung. On several occasions, blood 0:02:22.600 --> 0:02:26.080 was expectorated in small amounts. On the thirty eighth day 0:02:26.120 --> 0:02:30.160 of illness, recovery seemed to be proceeding uneventfully. On the 0:02:30.200 --> 0:02:33.120 morning of the forty fifth day of illness, however, the 0:02:33.160 --> 0:02:37.280 patient suddenly collapsed and died within a few minutes. Death 0:02:37.320 --> 0:02:57.720 was apparently due to a large embelis in the pulmonary vessels. 0:03:28.000 --> 0:03:32.400 That's a tough, tough story, yeah, and what a rollercoaster too, 0:03:32.960 --> 0:03:35.400 really is like you have no idea where it's going 0:03:35.480 --> 0:03:37.000 to go until you're there. 0:03:37.680 --> 0:03:40.840 Yeah. I don't know anything about the path of physiology 0:03:40.960 --> 0:03:44.520 of rift valley fever, so I'm very curious to know 0:03:44.560 --> 0:03:47.280 how well this fits in with like the clinical picture 0:03:47.360 --> 0:03:52.800 that has been seen, you know, not super well but interesting. 0:03:53.640 --> 0:03:58.600 But I can see how these things ended up happening, 0:03:58.680 --> 0:04:00.840 So we can when we talk at the pathology, we 0:04:00.880 --> 0:04:02.360 can kind of tie back into it. 0:04:03.080 --> 0:04:07.600 Okay, So that first hand account was from a paper 0:04:07.720 --> 0:04:12.680 by Schwenker and Rivers from nineteen thirty four titled Rift 0:04:12.760 --> 0:04:16.240 Valley Fever in Man Report of a fatal laboratory infection 0:04:16.480 --> 0:04:21.600 complicated by thrombo phlebitis. And this actually is the first 0:04:21.800 --> 0:04:26.279 recorded death due to Rift Valley fever. Oh interesting, I 0:04:26.320 --> 0:04:29.120 mean likely not the first death right humans, but the 0:04:29.160 --> 0:04:34.400 first recorded human death detailed recorded. Huh. Yeah. Hi. I'm 0:04:34.440 --> 0:04:37.760 Aaron Welsh and I'm Erin Alman Updike, and this is 0:04:37.960 --> 0:04:40.680 this podcast Will Kill You, And today we're talking about 0:04:40.880 --> 0:04:43.400 Rift Valley fever. We've had a lot of. 0:04:43.360 --> 0:04:45.840 Requests for this one, which I feel like is surprising 0:04:45.880 --> 0:04:48.680 because I knew almost nothing about it except I had 0:04:48.720 --> 0:04:51.279 heard there is Rift Valley fever, like I knew that 0:04:51.320 --> 0:04:54.040 it existed. I knew it was mosquito born. That's all 0:04:54.040 --> 0:04:54.400 I knew. 0:04:55.279 --> 0:04:58.200 Yeah, I say, I was like, oh, this is a 0:04:58.320 --> 0:05:02.279 dangerous virus. But I didn't really know much more than that. 0:05:02.600 --> 0:05:06.520 And I was kind of shocked when I got into 0:05:06.520 --> 0:05:08.240 the history of outbreaks. 0:05:08.839 --> 0:05:13.360 I am shocked at how little I knew, considering like 0:05:13.520 --> 0:05:17.200 that we were deep in disease ecology for so long. 0:05:17.480 --> 0:05:19.239 Oh yeah, I mean I still I would like flip 0:05:19.240 --> 0:05:24.000 through parasite books for fun. Yeah. Yeah, somehow just goes 0:05:24.040 --> 0:05:26.960 to show that there is no limit to the number 0:05:27.000 --> 0:05:32.640 of diseases and viruses and pathogens and parasites and fungi 0:05:32.760 --> 0:05:33.240 out there. 0:05:33.720 --> 0:05:36.200 Yeah, it's true. So with Valley fever is the one 0:05:36.240 --> 0:05:39.599 we're talking about today, but before we can tell you 0:05:39.680 --> 0:05:42.200 all about it and all the things that we learned, 0:05:42.760 --> 0:05:44.359 it's quarantine anytime. 0:05:44.040 --> 0:05:46.719 It is aaron. What are we drinking this week? 0:05:47.000 --> 0:05:49.520 We're drinking wolf in sheep's clothing. 0:05:50.839 --> 0:05:54.239 It'll make sense, it'll make sense. Sheep are involved. Wolf 0:05:54.320 --> 0:05:57.560 is the virus. I love to over explain a joke. 0:05:57.600 --> 0:06:01.839 It's well, we went back and forth by text. The 0:06:01.839 --> 0:06:04.040 wolf is the virus. The virus is the wolf. Yes, okay, 0:06:04.400 --> 0:06:09.919 that's a great name. What's in a wolf in sheep's clothing? 0:06:10.080 --> 0:06:15.000 A wolf in sheep's clothing is your basic concoction of mescal, 0:06:15.760 --> 0:06:20.880 grapefruit juice, a lemon lime soda of your choice, and 0:06:21.080 --> 0:06:23.320 you know, maybe a squirt of lime or something. 0:06:23.800 --> 0:06:27.600 And some halpinios write a little spicy mescal paloma. 0:06:27.839 --> 0:06:32.360 Yes, situationial the crucial muddled jalapenios, and we'll. 0:06:32.240 --> 0:06:34.760 Post the full recipe for that quarantini as well as 0:06:34.760 --> 0:06:38.400 the non alcoholic equally delicious plusy burrita on our website 0:06:38.440 --> 0:06:39.920 This Podcast will kill You dot Com and all of 0:06:39.960 --> 0:06:42.719 our socials, So if you're not already following us, you 0:06:42.760 --> 0:06:45.400 should because the picks are delicious. 0:06:45.760 --> 0:06:48.320 On our website This Podcast will Kill You dot Com, 0:06:48.360 --> 0:06:51.440 you can find all manner of things you know. There's 0:06:51.520 --> 0:06:54.840 transcripts for all of our episodes. You can find links 0:06:54.880 --> 0:06:57.720 to our bookshop dot org, affiliate account, our Goodreads list, 0:06:57.839 --> 0:07:02.800 music by Bloodmobile merch. We've got great merch we do. 0:07:03.360 --> 0:07:06.200 Links to Patreon, links to a submit your first hand 0:07:06.240 --> 0:07:09.600 account form, links to a contact us form. There's more 0:07:09.640 --> 0:07:10.040 there too. 0:07:10.520 --> 0:07:14.720 There's so much this podcast. Okay, dot com check it out. Yeah, 0:07:15.040 --> 0:07:18.280 if you haven't already, please check your podcast and make 0:07:18.280 --> 0:07:20.960 sure you're subscribed. If you haven't left us a review 0:07:21.360 --> 0:07:24.240 or a rating and you'd like to, now's your opportunity. 0:07:24.360 --> 0:07:25.360 You can do that right. 0:07:25.240 --> 0:07:27.560 Now, And we would so appreciate it. We would really 0:07:27.640 --> 0:07:29.840 love it. It really helps the show, So thank you. 0:07:30.040 --> 0:07:34.960 She's not lying, she's totally right. We appreciate it and 0:07:35.040 --> 0:07:41.560 it helps us. Well, then shall we get into this virus. 0:07:41.720 --> 0:07:44.240 Let's do it. Let's take a quick break and begin. 0:08:08.840 --> 0:08:11.360 I think part of what surprised me about how little 0:08:11.400 --> 0:08:15.920 I knew about Rift Valley fever is how much of 0:08:15.960 --> 0:08:20.320 a classic TPWKY story it really is. Yeah, I know 0:08:20.440 --> 0:08:22.320 that we are getting back to the roots of this 0:08:22.400 --> 0:08:25.240 podcast when I can go on the World Health Organization's 0:08:25.440 --> 0:08:28.800 website and find so much of the information that I'm 0:08:28.840 --> 0:08:31.800 looking for, and even more so when there's a page 0:08:31.840 --> 0:08:34.599 on the World Organization for Animal Health website. 0:08:35.520 --> 0:08:37.360 So buckle up. 0:08:37.400 --> 0:08:41.360 This is a really classic piece of TPWKY content. So 0:08:41.520 --> 0:08:44.640 Rift Valley fever is a disease that's caused by a 0:08:44.760 --> 0:08:47.440 virus called Rift Valley fever virus. 0:08:47.520 --> 0:08:48.480 It's not very creative. 0:08:49.360 --> 0:08:53.840 And this is an RNA virus in the genus flebovirus. 0:08:54.240 --> 0:08:55.319 I think that's how you say it. 0:08:55.920 --> 0:09:00.560 And I think that the phylogeny of this group viruses 0:09:00.600 --> 0:09:04.640 has changed relatively recently, But in any case, it's in 0:09:04.679 --> 0:09:07.800 the order Bunia viralus, which is the same group that 0:09:08.000 --> 0:09:12.920 includes hantaviruses and loss of fever virus and some others 0:09:12.960 --> 0:09:14.080 that we haven't yet covered. 0:09:14.559 --> 0:09:16.359 Have we done loss of fever. 0:09:16.360 --> 0:09:18.440 Er No, we haven't done loss of fever. But maybe 0:09:18.480 --> 0:09:20.920 people have heard of los of fever. I know, we 0:09:20.960 --> 0:09:24.600 haven't done it. Wow, Okay, there's aaron. There's so many 0:09:24.600 --> 0:09:27.559 that we haven't done yet. Yeah, but hantaviruses we have. 0:09:28.400 --> 0:09:32.560 And with the exception really of the hantaviruses and loss 0:09:32.600 --> 0:09:35.800 of fever and other arenaviruses, most all of the other 0:09:35.920 --> 0:09:41.360 viruses in this order Bunia viralis are transmitted primarily by 0:09:41.520 --> 0:09:45.560 arthropod vectors like ticks and mosquitoes, and rift Vali fever 0:09:45.840 --> 0:09:49.720 virus is no exception asterisk, but let's talk about it. 0:09:50.720 --> 0:09:54.120 So rift valley fever in humans is really considered a 0:09:54.240 --> 0:09:58.400 zoonotic disease, which means that primarily it's not affecting humans, 0:09:58.480 --> 0:10:02.040 it's infecting animals, and it's generally considered to be only 0:10:02.120 --> 0:10:05.840 these spillover events that end up causing disease in humans. 0:10:06.040 --> 0:10:09.600 So there has to generally be some kind of animal outbreak, 0:10:09.640 --> 0:10:12.960 which we call an epizootic before there is then a 0:10:13.080 --> 0:10:18.679 human outbreak. And this virus infects a pretty wide variety 0:10:18.880 --> 0:10:21.680 of animals, and the ones that end up being most 0:10:21.720 --> 0:10:25.840 important for us as humans are our livestock. So this 0:10:25.960 --> 0:10:31.120 virus infects cattle, sheep, goats, and other small ruminants and 0:10:31.360 --> 0:10:34.480 camels and sheep and goats tend to be the most 0:10:34.600 --> 0:10:41.000 severely affected. And it's transmitted to these livestock primarily by mosquitoes, 0:10:41.480 --> 0:10:45.520 but not just any one mosquito, no, no, no, whole 0:10:45.600 --> 0:10:51.800 bunches of mosquitoes in multiple different genera, mostly transmitted by 0:10:51.880 --> 0:10:56.080 eighties mosquitoes of dengey fever, yellow fever chickengunyet like all 0:10:56.160 --> 0:11:01.439 the viruses eighties mosquitoes as well as a qlex mosquitoes 0:11:01.600 --> 0:11:04.640 of like West Nile virus and Japanese encephalitis virus fame. 0:11:04.920 --> 0:11:09.959 It's so strange because usually viruses are so hyper adapted 0:11:10.120 --> 0:11:17.000 to their mosquito vector hosts, like that specific species. But 0:11:17.120 --> 0:11:19.480 this isn't. So What's how. 0:11:19.559 --> 0:11:23.760 I have so many questions, Aaron, about the path of 0:11:23.800 --> 0:11:28.240 physiology or the like the life cycle of this virus 0:11:28.280 --> 0:11:32.480 in mosquitoes because it it doesn't We don't have as 0:11:32.559 --> 0:11:38.320 much information as I expect, Okay, and it's really interesting. 0:11:38.480 --> 0:11:42.760 So there's at least like fifty different species of mosquito 0:11:43.400 --> 0:11:48.120 that have been found to harbor this virus, and the 0:11:48.200 --> 0:11:53.760 transmission is like usually when we picture like a transmission 0:11:53.920 --> 0:11:58.440 cycle among let's say you know vector host, maybe there's 0:11:58.440 --> 0:12:01.240 a secondary host. It's like a circ goal, right, the 0:12:01.320 --> 0:12:04.040 transmission of this virus. When you look at this cycle, 0:12:04.040 --> 0:12:06.440 it's not a circle. It's like a circle with a 0:12:06.480 --> 0:12:08.679 line and another line and like two other branches. 0:12:09.280 --> 0:12:12.920 It's get the mess create a peometry. 0:12:13.320 --> 0:12:17.600 Yeah, so how does it go? 0:12:18.000 --> 0:12:18.400 Really? 0:12:18.640 --> 0:12:22.199 Usually when we're covering a vector borne disease on this podcast, 0:12:22.280 --> 0:12:24.280 I can start like this, and I'll start like this 0:12:24.720 --> 0:12:27.800 for this episode. Ready, a female mosquito, it's always a 0:12:27.840 --> 0:12:31.440 female mosquito takes a blood meal from a host, let's 0:12:31.480 --> 0:12:35.160 call it a sheep for accuracy. It drinks up some 0:12:35.280 --> 0:12:37.800 of the virus in that blood meal because the sheep 0:12:37.840 --> 0:12:41.600 is infected. And after some amount of time in the 0:12:41.640 --> 0:12:46.199 mosquito and varying amounts of this virus moving through the mosquito, 0:12:46.800 --> 0:12:49.320 it maybe makes it to the salivary glands or something 0:12:49.360 --> 0:12:52.840 like that, and then that mosquito takes another blood meal, 0:12:53.440 --> 0:12:56.959 spits the virus into the host, and boom, Now you've 0:12:57.000 --> 0:13:04.160 completed the transmission cycle. And cycle can happen in Withfalley fever. 0:13:05.320 --> 0:13:09.480 But how long does it have to exist in the mosquito? 0:13:10.200 --> 0:13:11.800 How long does this virus have to be there? 0:13:12.120 --> 0:13:12.520 I don't know. 0:13:13.200 --> 0:13:15.240 What does it do inside this mosquito? 0:13:15.600 --> 0:13:16.160 I don't know. 0:13:16.160 --> 0:13:18.440 Where does it go? Does it travel to the salivary 0:13:18.480 --> 0:13:19.720 glands or does it not? 0:13:20.400 --> 0:13:24.600 I don't know. I don't know, Aaron, Okay, and I 0:13:24.800 --> 0:13:28.480 anticipate that the answer to this question is I don't know, 0:13:28.679 --> 0:13:34.600 but huh. Our different mosquito species differently capable of harboring 0:13:34.720 --> 0:13:35.959 transmitting the. 0:13:35.960 --> 0:13:41.080 Virus almost certainly yes, which one's more likely than less? 0:13:41.360 --> 0:13:44.400 I don't know. Here's where we. 0:13:44.320 --> 0:13:47.679 Can add another layer of complication. In addition to that 0:13:47.720 --> 0:13:52.360 transmission cycle, this virus can also be and is known 0:13:52.400 --> 0:13:55.960 to be, transmitted from female mosquitos into their eggs. This 0:13:56.040 --> 0:13:59.240 is called vertical transmission, and we know this happens at 0:13:59.320 --> 0:14:03.199 least in some way species of eighties mosquitoes, but maybe 0:14:03.200 --> 0:14:04.800 not in all species. 0:14:04.880 --> 0:14:09.079 We're not sure, which has huge implications for the distribution 0:14:09.200 --> 0:14:11.320 of this virus in the landscape and the potential for 0:14:11.360 --> 0:14:15.360 outbreaks to happen in subsequent years, even outside of like 0:14:15.440 --> 0:14:18.840 big outbreaks like the inter epidemic years or whatever. It 0:14:18.960 --> 0:14:20.200 sure does, Aaron. 0:14:19.960 --> 0:14:22.680 You're one hundred percent right, because it means that Mosquito 0:14:22.720 --> 0:14:26.560 babies are essentially born infected, so they can inject virus 0:14:26.600 --> 0:14:29.440 into their host with the very first blood meal that 0:14:29.440 --> 0:14:33.280 they take. So not only can this virus potentially persist 0:14:33.560 --> 0:14:37.720 like among different seasons without necessarily needing to have reservoir 0:14:37.800 --> 0:14:41.360 hosts that are infected, you also can then have viral 0:14:41.400 --> 0:14:45.239 transmission even if mosquitoes aren't living long enough to transmit 0:14:45.560 --> 0:14:48.320 from animal to animal to animal, because the very first 0:14:48.320 --> 0:14:51.840 blood meal that they take, they can potentially transmit this virus. 0:14:52.280 --> 0:14:56.000 Okay, so here's another question. Though it's not just the mosquito. 0:14:56.400 --> 0:14:59.600 It's not just the mosquitoes. It's not a question. 0:14:59.720 --> 0:15:03.560 But you know where I'm going with that. There's let's 0:15:03.640 --> 0:15:05.640 keep going, shall we. I said that this was a web, 0:15:05.960 --> 0:15:10.160 so we shall continue along this transmission web. Once an 0:15:10.200 --> 0:15:13.480 animal host is infected, and again mostly in this case 0:15:13.480 --> 0:15:18.840 we're talking about livestock, ruminants, sheep, cattle, goats, camels, all 0:15:18.880 --> 0:15:23.880 of these animals also have vertical transmission themselves. So if 0:15:23.880 --> 0:15:27.440 a pregnant animal gets infected from a mosquito, it will 0:15:27.480 --> 0:15:32.320 almost inevitably pass that virus through the placenta to their offspring, 0:15:32.360 --> 0:15:36.320 and this almost always causes spontaneous abortion or pregnancy loss. 0:15:36.840 --> 0:15:41.520 This virus can also be transmitted from mosquitoes to other wildlife, 0:15:41.720 --> 0:15:44.840 and we don't fully understand the whole wildlife cycle. 0:15:44.920 --> 0:15:46.520 That's just like a black box. 0:15:46.560 --> 0:15:48.680 We know that it happens, but we don't know what 0:15:48.840 --> 0:15:52.400 hosts are important. Are they amplifying hosts or are they not, 0:15:52.840 --> 0:15:53.320 et cetera. 0:15:53.520 --> 0:15:54.680 Are they maintenance hosts? 0:15:54.800 --> 0:15:57.160 Yeah, But then we get to humans. How do we 0:15:57.240 --> 0:16:02.520 get infected in this tangled web. Well, it could be 0:16:02.800 --> 0:16:05.400 the same way that our animal friends are getting infected 0:16:05.480 --> 0:16:09.680 via these mosquitoes, But what's far more common is that 0:16:09.840 --> 0:16:16.160 humans are infected from our infected animal friends themselves, either 0:16:16.200 --> 0:16:19.920 from direct contact with something like their blood, their raw milk, 0:16:20.040 --> 0:16:23.560 or other bodily fluids, directly getting into our eyes, mouth 0:16:23.640 --> 0:16:26.920 or other mucous membranes, or through breaks in our skin 0:16:27.400 --> 0:16:30.880 in the process of caring for or slaughtering these animals, 0:16:31.440 --> 0:16:36.640 or from inhaling aerosolized bodily fluids. So it's usually a 0:16:36.720 --> 0:16:41.120 kind of more direct transmission from animal to humans that 0:16:41.240 --> 0:16:44.400 ends up causing disease in humans. And then we as 0:16:44.480 --> 0:16:47.800 humans can also pass this virus through the placenta and 0:16:47.880 --> 0:16:52.320 potentially cause infection in a fetus. The only good thing 0:16:52.840 --> 0:16:57.880 thus far is that horizontal meaning human to human transmission 0:16:58.440 --> 0:17:01.880 has yet to be documented, and the same is true 0:17:01.920 --> 0:17:05.600 for direct transmission from animals to animals like among a herd. 0:17:06.240 --> 0:17:09.120 So then why is it that humans can get infected 0:17:09.119 --> 0:17:09.879 from animals? 0:17:10.200 --> 0:17:10.639 We don't know. 0:17:10.720 --> 0:17:12.440 Is it just because of the ways that we happen 0:17:12.520 --> 0:17:15.640 to be interacting with and handling their tissues and bodily fluids? 0:17:15.680 --> 0:17:16.119 I don't know. 0:17:17.000 --> 0:17:19.360 But that is the like good news that I can 0:17:19.400 --> 0:17:22.080 say about the transmission of this virus. 0:17:22.520 --> 0:17:25.240 Okay, I mean that makes sense because it's not like 0:17:25.280 --> 0:17:28.520 the animals are doing the slaughtering and inhaling the blood. 0:17:28.600 --> 0:17:32.440 It's it's yeah, humans are doing that. Okay. How many 0:17:32.520 --> 0:17:37.439 viral particles ooh? No? Idea great question though, okay, okay? 0:17:37.800 --> 0:17:41.240 And it is through the aerosolization, like, is it also 0:17:41.480 --> 0:17:45.399 contaminated surfaces? Is there? What's the durability of this virus 0:17:45.440 --> 0:17:46.200 in the environment. 0:17:46.520 --> 0:17:48.439 There's so many other questions. I could have tried to 0:17:48.440 --> 0:17:50.000 go down rabbit holes to answer that. I don't have 0:17:50.040 --> 0:17:56.280 the answers for aaron. Yes, so there's differential virulence and 0:17:56.880 --> 0:17:59.600 that's likely due to like like you asked how many 0:17:59.640 --> 0:18:02.359 viral articles does it take and things like that. People 0:18:02.480 --> 0:18:05.600 get more or less sick depending on what route they 0:18:05.600 --> 0:18:08.679 were more likely exposed to, and aerosol transmission seems to 0:18:08.680 --> 0:18:12.120 be the most virulent, so most likely to cause really 0:18:12.160 --> 0:18:15.640 severe disease is when it's you're inhaling it and it's 0:18:15.680 --> 0:18:18.800 going into your mucous membranes that way. The other common 0:18:18.800 --> 0:18:21.240 way that people get infected, and this could be from 0:18:21.280 --> 0:18:25.639 contaminated surfaces, but it's through contact with like broken skin, 0:18:26.200 --> 0:18:28.680 so like you have an injury and blood or something 0:18:28.760 --> 0:18:31.440 like that gets into your bloodstream from that. So those 0:18:31.480 --> 0:18:34.119 are kind of the two most common ways. There have 0:18:34.240 --> 0:18:36.600 been some cases of things like raw milk, which means 0:18:36.600 --> 0:18:39.879 that could be potentially an oral or a GI exposure, 0:18:40.440 --> 0:18:42.360 but we have just less data on that overall. 0:18:42.800 --> 0:19:00.000 Interesting. Okay, yes, this is maybe jumping ahead a little bit, 0:19:00.200 --> 0:19:03.359 but jen in an outbreak where it's not just livestock 0:19:03.440 --> 0:19:08.399 impacted but also humans, is there a any known breakdown 0:19:08.440 --> 0:19:12.760 between how people have gotten exposed, Like what proportion is 0:19:12.840 --> 0:19:15.679 mosquito versus direct contact that kind of thing. 0:19:16.200 --> 0:19:18.760 Of all the outbreaks that we have good data on 0:19:19.440 --> 0:19:24.719 primarily are happening from direct contact with animal fluids. It 0:19:24.800 --> 0:19:29.199 is very likely that mosquito born transmission absolutely plays a 0:19:29.280 --> 0:19:32.639 role in some outbreaks, but it seems that overall across 0:19:32.680 --> 0:19:35.719 the board, it is animal to human transmission that causes 0:19:35.760 --> 0:19:39.080 the vast majority of human cases. Okay, which means that 0:19:39.119 --> 0:19:41.200 the people at highest risk are people who work in 0:19:41.200 --> 0:19:44.920 industries where they are coming into contact with animals. Okay, 0:19:45.600 --> 0:19:48.920 But as I'm sure you know, and we'll probably talk about, 0:19:48.960 --> 0:19:52.240 some of the historic outbreaks have been very large, which 0:19:52.280 --> 0:19:54.760 means that certainly there's other things that are going on, 0:19:54.920 --> 0:19:58.760 and why in those cases did the outbreaks get so big. 0:19:58.880 --> 0:20:02.760 They're presum probably must have been also mosquito borne transmission happening. 0:20:03.960 --> 0:20:06.800 So yes, it definitely can happen. But does it also 0:20:06.840 --> 0:20:09.280 just depend on, like our mosquitos more likely to bite 0:20:09.320 --> 0:20:12.119 humans or to bite animals, and what mosquito species are 0:20:12.160 --> 0:20:15.000 circulating in those regions, because again, this is so many 0:20:15.080 --> 0:20:19.879 different mosquito species. So yeah, there's a lot, there's a 0:20:19.920 --> 0:20:23.240 lot of layers, and we don't have great data on 0:20:23.359 --> 0:20:26.200 a lot of details. 0:20:25.600 --> 0:20:28.960 On a lot of these outbreaks. Yish that we had 0:20:28.960 --> 0:20:31.560 more data. I wish that we had more data. I mean, 0:20:32.040 --> 0:20:33.560 don't we all don't we? 0:20:34.040 --> 0:20:37.840 Yes, we do know some more about like what does 0:20:37.840 --> 0:20:40.320 this disease do, Like what does it look like if 0:20:40.600 --> 0:20:44.119 an animal or if a person gets rifally fever. Unsurprisingly, 0:20:44.359 --> 0:20:46.360 given that this is a virus that infects so many 0:20:46.359 --> 0:20:51.280 different species, it presents very differently across different animals, but 0:20:51.359 --> 0:20:57.160 even within humans it can present very differently across the board. Though, 0:20:57.200 --> 0:21:01.639 we know that there's two main cell types in mammalian 0:21:01.720 --> 0:21:05.880 bodies that this virus is predominantly infecting, and everyone who 0:21:05.920 --> 0:21:08.719 listens to this show is well aware at this point 0:21:08.760 --> 0:21:12.639 that a virus has to infect a host cell in 0:21:12.720 --> 0:21:15.679 order to use our machinery to replicate. So which cells 0:21:15.720 --> 0:21:19.680 it's infecting tend to be really important in what kind 0:21:19.720 --> 0:21:22.800 of symptoms and what kind of disease we see. So 0:21:22.920 --> 0:21:25.280 in the case of rift Valley fever, the two main 0:21:25.400 --> 0:21:29.080 cell types that this virus is infecting are liver cells, 0:21:30.000 --> 0:21:32.480 so we'll talk about what that ends up doing, and 0:21:32.560 --> 0:21:36.400 then monocytes, which are a type of white blood cell. 0:21:36.440 --> 0:21:41.560 And so especially in severe cases, the liver is one 0:21:41.600 --> 0:21:44.439 of the main sites of damage. So what does that 0:21:44.520 --> 0:21:49.359 end up actually looking like If we look at animals Again, 0:21:49.480 --> 0:21:52.000 the symptoms will vary depending on the type of animal 0:21:52.040 --> 0:21:55.360 that's infected, as well as how old that animal is, 0:21:55.520 --> 0:22:01.720 because universally, young animals so fetuses as well as newborn animals, 0:22:01.960 --> 0:22:07.520 are much more severely affected than older animals. But in general, 0:22:07.760 --> 0:22:10.520 in almost all animals that are infected, all of these 0:22:10.560 --> 0:22:14.320 livestock animals, we see things like fever. We'll see the 0:22:14.400 --> 0:22:18.440 animal stop eating, they stop like moving about, They don't 0:22:18.480 --> 0:22:20.560 really like walk around or get up and go around. 0:22:20.840 --> 0:22:25.800 They become really like listless and lethargic. Especially in sheep, 0:22:25.880 --> 0:22:30.240 you might start to see evidence of gi inflammation, abdominal pain, 0:22:30.480 --> 0:22:34.800 bloody diarrhea, and these animals are like visibly in pain 0:22:34.880 --> 0:22:38.720 and uncomfortable. But the way that this virus ends up 0:22:39.040 --> 0:22:44.560 wiping out entire populations of livestock is because it passes 0:22:44.640 --> 0:22:48.480 through the placenta and then causes spontaneous abortions in pregnant 0:22:48.480 --> 0:22:53.399 animals and then has massive mortality rates in newborn and 0:22:53.480 --> 0:22:58.200 young animals. So in these livestock herds, especially in lambs 0:22:58.240 --> 0:23:00.680 and kids which are baby goats, the more mentality rate 0:23:00.720 --> 0:23:03.760 can be as high as seventy to one hundred percent. 0:23:04.320 --> 0:23:09.199 It's devastating it's devastating, and even in adult sheep and 0:23:09.240 --> 0:23:12.720 things like baby cows or calves and adult cattle, the 0:23:12.800 --> 0:23:16.520 mortality rates can be as high as twenty to seventy percent. 0:23:16.680 --> 0:23:20.560 So this is a very lethal infection for livestock animals. 0:23:22.119 --> 0:23:26.320 When it comes to humans, there is a really wide 0:23:26.720 --> 0:23:32.120 range of how this disease can present. Most papers across 0:23:32.119 --> 0:23:35.639 the board estimate that about fifty percent of people who 0:23:35.720 --> 0:23:40.320 are infected are essentially asymptomatic, like don't really show any 0:23:40.320 --> 0:23:45.480 symptoms whatsoever. And most people who do have symptoms will 0:23:45.520 --> 0:23:49.959 have a relatively mild disease and only a small percentage 0:23:50.000 --> 0:23:53.880 And most papers say maybe one to two percent develop 0:23:54.080 --> 0:23:57.119 severe symptoms, and we'll talk about what those severe symptoms 0:23:57.200 --> 0:24:02.640 look like. But I want to caveat early on those numbers, 0:24:02.760 --> 0:24:06.719 because a it seems like maybe that one to two 0:24:06.800 --> 0:24:12.080 percent is an underestimate for recent outbreaks or more modern outbreaks, 0:24:13.359 --> 0:24:16.240 And some papers cite this number instead of saying one 0:24:16.280 --> 0:24:18.720 to two percent of all cases, they'll say it's like 0:24:18.800 --> 0:24:22.119 eight to ten percent of symptomatic cases, Okay, And I 0:24:22.160 --> 0:24:25.520 feel like looking at it that way really changes your 0:24:25.560 --> 0:24:29.479 perspective on this disease, because as we'll go through some 0:24:29.480 --> 0:24:33.240 of these symptoms. This can be incredibly terrifying and really severe, 0:24:33.560 --> 0:24:36.560 and so I think trying to understand how big are 0:24:36.600 --> 0:24:38.800 these outbreaks that we're talking about and how many people 0:24:38.840 --> 0:24:42.960 are affected are really really important. So let's talk about 0:24:43.000 --> 0:24:45.320 what it ends up looking like. If somebody is going 0:24:45.359 --> 0:24:47.200 to show symptoms of refali fever. 0:24:48.160 --> 0:24:49.920 Symptoms usually start between. 0:24:49.640 --> 0:24:53.119 Two to six days after exposure, and it usually starts 0:24:53.160 --> 0:24:57.600 as the name suggests, with a fever along with a headache. 0:24:58.000 --> 0:25:01.879 You'll have muscle or joint pain. Very often we see 0:25:01.960 --> 0:25:05.840 some like neurologic symptoms like vertigo or like in the 0:25:05.840 --> 0:25:08.600 first hand account that photophobia. 0:25:08.200 --> 0:25:09.600 Like it hurts to look at light. 0:25:10.000 --> 0:25:14.560 Yeah, you might have nausea or vomiting, and then if 0:25:14.560 --> 0:25:18.080 it remains a mild case, then this might last anywhere 0:25:18.080 --> 0:25:20.639 from like a few days, like four days to a 0:25:20.680 --> 0:25:23.919