Measles Virus – Paramyxoviruses

by Sean Elliott, MD

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    00:01 So, let's look first at measles virus.

    00:03 This is a very, unfortunately, increasingly common virus in parts of the world where there are populations that are under vaccinated, currently, in the States and other parts of the world.

    00:16 There's an incubation period of around 1-2 weeks, so 7-13 days, per the slide.

    00:22 And after the initial infection of the upper respiratory tract and localized lymph nodes, with a secondary viremia, one can have attack to all the areas which you see in the slide.

    00:33 So, the conjunctiva, the urinary tract, the small blood vessels, lymphatic system, even throughout the central nervous system.

    00:41 And how far the viremia spreads and how aggressive it is, meaning that the viral load, really accounts for how severe the symptoms of the accompanying measles actually are.

    00:53 So, what does measles look like? First, there is a prodromal period, which is very nonspecific.

    01:00 However it -- I mean, it starts with fevers, malaise, etc., and then the patients develop the classic 3 C's: cough, coryza, conjunctivitis.

    01:12 The cough. It's a brassy, deep cough, almost like a smoker's cough, which sometimes is productive of a deep sputum.

    01:20 The coryza is typically starting as clear and then it becomes even a mucopurulent nasal discharge.

    01:27 And the conjunctivitis.

    01:29 Erythematous injection of the full conjunctiva with a very copious tearing of the eyes.

    01:36 And along with that, sort of a photo phobia.

    01:39 So, it's at this time that the patient may mistakenly be thought to have something like adenovirus, a cause of pink eye, or even influenza So it's still despite the presence of the classic 3 C's, a nonspecific presentation.

    01:57 If one has a clinical suspicion, and if so, I take my hat off to you because it's hard to make that clinical judgment, but if one does, on day 3 of this prodromal period, one can start to see Koplik spots inside the mouth.

    02:13 And with the picture in front of you, the dark arrow is showing one of those.

    02:18 Koplik spots are sort of bluish-gray, small, like maybe 1 millimeter in diameter, papules on the buccal mucosa that have a slight surrounding red halo.

    02:29 They're easy to miss unless you're specifically looking for them.

    02:33 And if you see the Koplik spots in the setting of the 3 C's we just talked about, you have made your clinical diagnosis of measles.

    02:41 Isolate and go on about your business.

    02:44 However, many times, those presentations are missed, and then a maculopapular rash which has been nicknamed a morbilliform rash, a measles rash, kind of like defining it by the name of the infection, which is not very helpful.

    02:59 But a densely erythematous, maculopapular rash starts and the distribution and progression is very key here.

    03:08 It starts up at the head, starts cranially, and it moves caudally toward the tail, as it were, toward the extremities.

    03:15 But there is a clearing of the rash as it moves from section to section over the period of 3-4 days.

    03:23 So, with, still present, a conjunctivitis and one can see this dense, maculopapular rash on the face.

    03:33 And then as it moves down toward the trunk, it may start to clear on the face and the conjunctivae may start to clear up as well.

    03:40 By the time we get down to the lower abdomen and the pelvis, the areas of the neck and above may be either completely cleared or pretty close.

    03:48 So, the progression is key to a clinical diagnosis of measles.

    03:54 Unfortunately, there's no treatment.

    03:56 There is prevention, as we'll talk about shortly.

    03:59 But regardless of, you know, how severely ill or not severely ill the patient is, there are still complications.

    04:08 These patients can progress to serious or severe measles, with pneumonia, These patients can progress to serious or severe measles, with pneumonia, with encephalitis, with seizures, with coma, the whole 9 yards.

    04:18 And then after they've recovered from this spontaneously, and it may take several weeks for that, they are at risk for developing SSPE, subacute sclerosing panencephalitis.

    04:30 This is a nasty.

    04:31 This is very much, in appearance, like Alzheimer's disease, but it progresses, from start to finish, over a period of maybe months to at most, years, 1-2 years.

    04:43 So think of these patients as losing cognition, losing awareness, losing body function, etc., but very, very rapidly.

    04:52 So this is horrible.

    04:53 And, of course, the whole thing is preventable via vaccine.

    04:57 How to make the diagnosis.

    04:59 Well, as mentioned, there -- I've given you multiple clinical clues.

    05:02 The three C's: a progressive rash with clearing as one goes to the caudal region, and then, of course, the appearance of the rash itself.

    05:12 But once one has a clinical suspicion, molecular diagnosis currently is the best way to go.

    05:18 So an RT-PCR will pick up the RNA of the virus itself.

    05:25 Transmission, as mentioned before, as with the other viruses, it's respiratory droplets.

    05:30 Patients can be contagious prior to the onset of symptoms, prior to that prodrome, unfortunately, so during the incubation period of 1-2 weeks, patients can be infectious.

    05:41 Which is unfortunate because it allows for epidemics or outbreaks of the disease to occur if one has a unvaccinated or under vaccinated population.

    05:52 So, prevention, that vaccine.

    05:55 Very effective.

    05:56 A live, attenuated vaccine which we start to give to infants at 12-15 months of life with the booster at 4-5 years of life.

    06:04 Currently, the vaccine is part of a combination vaccine, the MMR: measles, mumps, rubella, and all 3 are live and attenuated.

    06:13 For patients who are unvaccinated, under vaccinated, maybe have only received 1 vaccine, or their vaccine status is unknown, if they are exposed to, in an epidemic setting, , a known case of measles, they can be given measles immunoglobulin.

    06:31 So passive immunization to help them be protected, at least, for several weeks against developing further disease.

    About the Lecture

    The lecture Measles Virus – Paramyxoviruses by Sean Elliott, MD is from the course Viruses.

    Included Quiz Questions

    1. 7–13 days
    2. 1–4 days
    3. 14–18 days
    4. 19–24 days
    5. 25–30 days
    1. Koplik's spots
    2. Roth spots
    3. Bitot's spots
    4. Forchheimer spots
    5. Canker sores
    1. ...maculopapular.
    2. ...petechial.
    3. ...vesicular.
    4. ...eczematous.
    5. ...purpuric.
    1. Subacute sclerosing panencephalitis
    2. Japanese encephalitis
    3. West Nile encephalitis
    4. Toxic-metabolic encephalopathy
    5. Wernicke encephalopathy

    Author of lecture Measles Virus – Paramyxoviruses

     Sean Elliott, MD

    Sean Elliott, MD

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