Hepatitis A Virus (HAV) – Picornaviruses

by Sean Elliott, MD

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    00:01 And then finishing up with hepatitis A virus.

    00:04 This virus is resistant to acid, which makes sense because it is typically a fecal- oral transmission, surviving passage through the gastric mucosa and the acid load, and then entering itself and causing eventual disease.

    00:19 Transmission, fecal-oral, but so, too, aerosols can deliver this virus.

    00:24 The picture you see is a transmission electron microscopic graph -- micrographic image, sorry, of hepatitis A, again, clustered and looking very beautiful in clustered format.

    00:36 So, here is the pathogenesis for hepatitis A virus.

    00:40 The primary replication occurs, again, in the point of entry, so oropharynx, passaging through the stomach to intestinal epithelium.

    00:49 Then the patients develop viremia after that first lytic phase, and the viruses then attack the hepatocytes.

    00:58 At the initial point of contact, binding, and insertion of the virus into the hepatocytes, there's minimal damage Even as the viruses are passaging themselves, again, creating new additional virions, which are excreted into the bile, through the common bile duct and into the stool for up to 10 days, there is still a limited response with the exception of a systemic immune or inflammatory response, which gives you the initial symptoms.

    01:26 But as yet, there's not a specific attack on the hepatocytes.

    01:30 That comes later after the prodromal and preicteric symptoms.

    01:35 Prodromal symptoms as immune reaction is starting to develop in exposure to those virions, is low-grade fever, malaise, anorexia; your common typical viral syndrome.

    01:46 The preicteric symptoms, so this is as the immune system is starting to rev up and starting to recognize that indeed, we have some damaged hepatocytes to address.

    01:57 This starts to get much more gastrointestinal in its approach.

    02:00 So, nausea, vomiting, the abdominal pain is crampy and nonspecific.

    02:06 Many patients describe it as lower down instead of over the liver, which is somewhat interesting, but pain can be referred anywhere.

    02:13 Patients also have fevers which increase in nature and they start to have rigors, generally feeling, again, like a miserable patient with the flu.

    02:23 However, the flu is not followed, in most cases, by jaundice.

    02:27 And when the patient then progresses to the icteric disease, this is when they're now starting to get evidence of a transient, thankfully, but acute liver failure.

    02:37 Inflammatory reaction targeting those infected analytic hepatocytes, which is causing decrease passage of bile, and a backup of bilirubin into the body.

    02:49 So these patients have jaundice.

    02:51 Their urine is excreting very dark evidence of bilirubin.

    02:55 When one checks their liver numbers, their liver tests, the transaminases, the AST, ALT, all of these are elevated.

    03:04 That all goes with hepatitis A virus.

    03:07 So, diagnosis, both clinical, but also, a serologic assessment for immunoglobulin M antibody to the hepatitis A virus.

    03:17 Why IgM? Because we actually now have vaccine product which can create an IgG protection and that is mostly protective.

    03:26 It has a very good efficacy, but yet, like nothing else, is not 100%.

    03:32 So, serologic detection of immunoglobulin would suggest acute infection with hepatitis A, and there are very few things to cause a false positive Treatment.

    03:42 Well, actually treatment is prevention as best as we can because hepatitis A is sewage or fecal-associated, so having proper treatment of the water supply through the municipal water supply.

    03:54 Chlorine is effective in this.

    03:56 Certainly, good hygienic practices.

    03:59 Again, washing hands, wherever and whenever you go anyplace.

    04:03 Avoidance of contaminated food and water.

    04:05 Well, kind of hard to do if you don't know that they are contaminated, and because hepatitis A is a fecal-oral transfer, one could have exposure to a friend, a food server, a healthcare worker, who is actively viremic and expressing hepatitis A contagious virions into their stool, and then could be exposed through their hands.

    04:29 So, for yourself, washing hands is important.

    04:32 Especially for travelers and those living in parts of the world that are endemic for hepatitis A or exposure to that, there is a very successful vaccine, as I just mentioned, which is highly recommended.

    04:47 In fact, in the States, it's part of a routine, recommended, or even required vaccine schedule for pre- school aged children because hepatitis A is now becoming quite so common.

    04:59 Treatment.

    05:00 Mostly for those who are immunocompromised and unable to respond to the virus on their own is to give immunization with hepatitis A-specific immunoglobulin, or even polyclonal immunoglobulin.

    05:12 However, most of the rest of us are able to make an appropriate immune response, and we just need enough time to get past the active infection, and to recover fully, 100%.

    05:24 So, this is a longer session is discussing some of the most mportant viruses in terms of, especially pediatrics, with exposure to the enteroviruses as a whole.

    05:34 Probably key to remember here is that the disease associated with each of these viruses has so much to do with the tropism, the target of the virus in terms of where it causes its disease.

    05:48 Viruses all cause disease in 1 way; by lysing their host cell and precipitating an immune reaction.

    05:55 And when that immune reaction targets a disease cell in the liver, or the brain, or the kidneys, or the throat, or the hands and the feet, all causes different manifestations.

    06:05 Remember those and you'll be good.

    About the Lecture

    The lecture Hepatitis A Virus (HAV) – Picornaviruses by Sean Elliott, MD is from the course Viruses.

    Included Quiz Questions

    1. IgM
    2. IgA
    3. IgD
    4. IgE
    5. IgG
    1. Inactivated
    2. Live attenuated
    3. Subunit
    4. Recombinant
    5. Toxoid
    1. Feco-oral route
    2. Sexual contact
    3. Droplet spread
    4. Infected mosquito bite
    5. Infected tick bite

    Author of lecture Hepatitis A Virus (HAV) – Picornaviruses

     Sean Elliott, MD

    Sean Elliott, MD

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