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posted by takyon on Saturday July 04 2015, @11:30PM   Printer-friendly
from the jenny-mckillthy dept.

Health officials on Thursday confirmed the country's first measles death since 2003, and they believe the victim was most likely exposed to the virus in a health facility in Washington state during an outbreak there. The woman died in the spring; a later autopsy confirmed that she had an undetected measles infection, the Washington State Department of Health said in a statement. The official cause of death was announced as "pneumonia due to measles."

According to the U.S. Centers for Disease Control and Prevention, 178 people from 24 states and the District were reported to have measles from Jan. 1 through June 26 of this year. Two-thirds of the cases, the CDC noted, were "part of a large multi-state outbreak linked to an amusement park in California."

Measles were effectively eliminated in the United States in 2000, according to the CDC. Health officials have said that the disease made a comeback recently, in part because of a growing number of adults deciding to delay or abstain from vaccinating their children. Last year brought the highest number of recorded measles cases since 2000, according to the CDC. Earlier this year, President Obama acknowledged the concerns some have about effects of vaccines but said: "The science is pretty indisputable." "You should get your kids vaccinated — it's good for them," Obama said. "We should be able to get back to the point where measles effectively is not existing in this country."

takyon: Celebrity critics recently denounced California's new mandatory vaccine law.


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  • (Score: 1) by khallow on Sunday July 05 2015, @02:48PM

    by khallow (3766) Subscriber Badge on Sunday July 05 2015, @02:48PM (#205291) Journal

    It is true the exposure depends upon the susceptibles being in the same location, but they do not have to be there at the same time.

    Hours is not a significant length of time. And the problem is that you don't have a population mostly of susceptibles. If it really were that easy to spread measles in a vaccinated population, we would have had those epidemics already.

    And honestly, the effect of anti-vaxxers on this has to be a rounding error.

    Not at all. As long as the population of unimmunized is sparse and poorly connected, it's not an issue. But if you have a well connected population, even one that is small part of a larger population, then you have the means to spread measles throughout a larger population that has partial immunity.

  • (Score: 0) by Anonymous Coward on Sunday July 05 2015, @11:26PM

    by Anonymous Coward on Sunday July 05 2015, @11:26PM (#205403)

    You seem to be assuming that measles spreads primarily via direct contact. That is what they assumed in the 1960s, but it is not true. Measles is airborne and that makes the herd immunity concept much more complex. Here is a retrospective (from 1980) by the head of the CDC during the introduction of the measles vaccine explaining why that idea is in error:

    Although the concepts of epidemic theory can be generalized without limit, the mathematical expressions of the theory had to be extremely simplified in order to be workable for the average student. A key assumption was that contagious diseases were spread by contact, that the contact rate of each case or
    carrier was reasonably constant under any given set of conditions, and that the major factors leading to variation in epidemic patterns were determined by environmental circumstances, particularly crowding, and by the proportion of susceptibles in the population. The studies of Chapin and many others of the high
    secondary attack rates among susceptible household contacts of many contagious diseases, particularly measles, supported these views. The Epidemic Theory, as
    expounded in the 1930s and 40s. left no room for airborne infection and ignored the concept of the occurrence of the occasional dangerous carrier or "superspreader" that is now clearly recognized in many diseases.

    http://www.ncbi.nlm.nih.gov/pubmed/?term=6939399 [nih.gov]

    • (Score: 1) by khallow on Monday July 06 2015, @02:19AM

      by khallow (3766) Subscriber Badge on Monday July 06 2015, @02:19AM (#205452) Journal

      You seem to be assuming that measles spreads primarily via direct contact. That is what they assumed in the 1960s, but it is not true. Measles is airborne and that makes the herd immunity concept much more complex.

      No, I believe that distinction is wholly irrelevant. For example, the two phenomena mentioned, air-borne contact and the somewhat higher number of contacts, "superspreader" don't actually change the model. You still have to be in near proximity to an infected person in order to catch the disease yourself.

      But even if the contact model were somehow in enough error to be irrelevant as a model of the spread of measles, it still is irrelevant to our discussion. Herd immunity is not a consequence of physical contact-only models. It is instead a consequence of the physical reality and backed by decades of observation of measles and other diseases. And the obvious here is that measles has had plenty of opportunity to become a "gigantic epidemic" since vaccination and instead it has nearly vanished despite plenty of reseeding from places that still have measles.

      • (Score: 0) by Anonymous Coward on Monday July 06 2015, @02:48AM

        by Anonymous Coward on Monday July 06 2015, @02:48AM (#205458)

        You are incorrect . The R0 values are used to calculate the percent of the population to be vaccinated for eradication (1/R0). RO depends crucially on the effective contact rate, which, as explained by Langmuir, was assumed to be relatively stable from person to person and day to day. Applying these models to a situation where one person may expose thousands of others in an hour will be misleading. Read the paper, Langmuir explains how *he* made this error in the 1960s when predicting the effectiveness of measles vaccination.

        https://en.m.wikipedia.org/wiki/Basic_reproduction_number [wikipedia.org]

        • (Score: 1) by khallow on Monday July 06 2015, @03:07AM

          by khallow (3766) Subscriber Badge on Monday July 06 2015, @03:07AM (#205465) Journal

          You are incorrect .

          Then where's the argument that I'm wrong? It's not important that contact rate is relatively stable as long as the collective R0 rate is below 1. For example, suppose we consider the case of the one person who infects thousands. As a result, due to 15% immunity rate, only a few hundred will actually show symptoms of measles. In turn, these people will be considerably less infectious than the first person (since superspreaders are by historical observation rare) and infect maybe a few hundred more by the time the bout of infection peters out a few weeks or months later. Your gigantic epidemic causes perhaps a few thousand people in the worst case to show the symptoms of measles.

          • (Score: 0) by Anonymous Coward on Monday July 06 2015, @05:41AM

            by Anonymous Coward on Monday July 06 2015, @05:41AM (#205498)

            as long as the collective R0 rate is below 1

            It is not R0 that directly matters but the effective reproductive rate R=R0*S/N, where S=# Susceptibles and N=Total Population. When R is less than 1 but the disease is not eradicated, S will constantly increase. "Superspreading" is not (only) a property of the person, but the environment and population. Note that these calculations assume a homogeneously mixing population which may or may not be a good enough approximation of reality.

            The second scenario represents the impact of a vaccination programme that reaches high levels of coverage (85% of all new-borns) which are, nevertheless, not high enough to lead to eradication of the agent. However, for the first 15 years after the introduction of vaccination, it appears as if eradication has been achieved, there are no infections. Then, suddenly, a new epidemic appears as if from nowhere. This is an illustration of a phenomenon known as the ‘honeymoon period’. This is the period of very low incidence that immediately follows the introduction of a non-eradicating mass vaccination policy. This happens because susceptible individuals accumulate much more slowly in a vaccinated community. Such patterns were predicted using mathematical models in the 1980s6 and have since been observed in communities in Asia, Africa and South America7. Honeymoon periods are only predicted to occur when the newly introduced vaccination programme has coverage close to the eradication threshold.

            http://www.ncbi.nlm.nih.gov/pubmed/12176860 [nih.gov]

  • (Score: 0) by Anonymous Coward on Monday July 06 2015, @12:55AM

    by Anonymous Coward on Monday July 06 2015, @12:55AM (#205435)

    If it really were that easy to spread measles in a vaccinated population, we would have had those epidemics already.

    I agree, this is surprising. Along those lines, it is interesting that this woman was asymptomatic. How many people *are* getting measles?

    Perhaps the classic symptoms only occur in 10-20% of the population. That would explain a lot actually. Before the vaccine they thought they were only recording ~17% of the US cases, currently ~15% of US people react to the vaccine with a rash and fever... I wonder if there is a haplotype related to measles infection found in 10-20% of the US population.