Chaos versus noisy periodicity: alternative hypotheses for childhood epidemics

Article Abstract:

The patterns of occurrence of measles and chickenpox in regions where vaccination is not performed were analyzed to determine whether epidemics of these diseases occur in a periodic or chaotic (disorderly) fashion. Data from eight large North American and European cities and two small islands were evaluated using the methods of spectral analysis. Predictions of a standard epidemiological model that categorizes people according to whether they are susceptible, exposed, infectious, or recovered (the SEIR equations) were compared with the real-world data. The results indicate that epidemics of chickenpox in large populations occur in periodic cycles with a period of one year. Measles epidemics, however, do not show such a pattern. Three hypotheses are considered to explain these fluctuations: that they have a probabilistic origin; that they represent a high-low two-year cycle, with noisy perturbations; and that they are chaotic. The last explanation is considered the most likely, based on real-world data and epidemiological models. Thus measles epidemics probably occur in a chaotic, meaning disorderly and unpredictable, pattern. (Consumer Summary produced by Reliance Medical Information, Inc.)

Demographic aspects, Measles, Chickenpox, Communicable diseases in children, Pediatric communicable diseases

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Russian chaos breeds diptheria outbreak

Article Abstract:

A serious epidemic of diptheria has caused more than 80,000 cases in Russia and the other former Soviet Republics. Health officials blame the outbreak on inadequate vaccination against the disease and a poor public health response at the beginning of the epidemic.

Health aspects, Russia, Public health, Diphtheria

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Estimating chaos in an insect population

Article Abstract:

A study that used estimates from a deterministic skeleton to identify transitions to chaos in flour beetle populations may have ignored the random component in population dynamics. Arguments supporting and opposing this view are presented.

Research, Chaos theory, Chaotic systems, Insect populations

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