Measles surveillance in Canada: 2015

BACKGROUND

Measles has been eliminated in Canada since 1998. Every year, the Public Health Agency of Canada presents epidemiologic evidence to the Pan American Health Organization (PAHO) to verify that measles elimination continues in Canada.

OBJECTIVE

To describe measles activity in Canada for 2015 as updated evidence for continued measles elimination status.

METHODS

Measles surveillance data were captured by the Canadian Measles and Rubella Surveillance System (CMRSS) and the Measles and Rubella Surveillance (MARS) pilot project and assessed for distribution by demographics and risk factors. Outbreak characteristics were summarized and genotypic and phylogenetic analyses were conducted and described. Surveillance data for 2015 were evaluated against PAHO's essential criteria for measles elimination status.

RESULTS

In 2015, the incidence of measles in Canada was 5.5 cases per 1,000,000 population, with 196 cases across four provinces. The majority of cases (87.2%, n=171) were not immunized and both age-specific incidence rates and case counts were highest among those aged 10 to 14 years (29.5 cases per 1,000,000 population, n=55). This was due in large part to a sizeable outbreak in a non-immunizing religious community. Overall, 10.7% (n=21) of cases were hospitalized. Genotype information was available for 100% of measles events (4/4 outbreaks and 6/6 sporadic cases). Canada met or partially met most of PAHO's criteria for verification of measles elimination.

CONCLUSION

Although importations and areas of low immunization coverage continue to challenge Canada's elimination status, surveillance data for 2015 provides strong evidence that measles elimination has been maintained.

A proliferation of pathogens through the 20th century

A substantial proportion of immunologists, microbiologists and health professionals--and, indeed, many dictionaries--currently regard the term pathogen as a synonym for a pathogenic organism (most often a micro-organism). I will argue that this is a distortion of its original meaning--'a specific causative agent of disease'. An analysis of the historical use of the term pathogen together with a comparison of the meanings of pathogen, pathogenic and pathogenesis suggest that this was an insidious change. It began as a convenient abbreviation, escalated into a misappropriation and is now lodged in bio-medicine's popular lexicon. In science, we should resist the pressures brought about by the mass action of common usage--unless there is a good, logical reason to accept this change. I propose that this common usage results in a distortion and leads to conceptual confusion, particularly when we try to understand the interaction between hosts and invasive organisms. This drift, in which pathogen becomes exclusively a living organism, is corrupting. There is a strong case for correcting and reversing it.

Tissue Homeostasis and Immunity – More on Models

This article continues the ongoing debate around models of the immune system. Earlier contributors have paid much attention to the various processes that lead to adaptive immune system aggression or tolerance. They have often based their discussions around facts that have been established by experimental investigation. However, both the observation and interpretation of these facts have been influenced by the function--or system goal--that is believed to have generated them. The perception of this function (of all or part of the immune system) is influenced by long established theories in immunology (e.g. horror autotoxicus, clonal deletion in utero, pathogen elimination, clonal selection, auto-immunity and so on) which, for many, have become enshrined as facts. One function that has had less consideration and has not been extensively investigated is the maintenance of tissue homeostasis. When the immune system is viewed from this perspective, the facts invite alternative interpretations. Whilst this perspective may not necessarily be the only valid one, let alone a correct one, viewing things this way--at least briefly--might help to expose hidden assumptions. It also emphasizes that the immune system is a system and, as such, it can by analysed through the principles of general systems theory.

From terra firma to terra plana--danger is shaking the foundations: deconstructing the 'immune system'

The paradigm of an immune system presumes that a system arose specifically to combat infection -- hence its name. This paradigm gained credibility with the discovery of antibodies and anamnestic immunity, even though these are relatively late arrivals in evolution. Another presumption has been that thymus-dependent T cells are responsible for discriminating self from non-self. Subsequent opinion has crystallized around these presumptions. This paradigm is flawed. Transforming it into a morphostatic system resolves the problems. There is, arguably, no such thing as an immune system.

Morphostasis: an evolving perspective

In an earlier article, I proposed a pathway by which morphostasis (tissue homeostasis) may have evolved. It began in single-celled organisms and culminated in the mammalian immune system. This evolutionary path is now traced from its source--the intracellular surveillance within an isolated cell of its own internal health. Morphostasis sequentially incorporates heat shock proteins, apoptosis, cell adhesion molecules, complement components, gap junctions, phagocytes, natural killer cells, cytotoxic T-cells, helper cells and antibodies. I propose that the sequence leading to the insertion of gap junctions is an ancestor of the complement attack sequence. Although contentious, this deduction is intriguing, since numerous, minimal clues support the proposition. The broad hypothesis emphasizes a theme that may prove to be a useful framework on which to hang a better understanding of immunology and embryology. It highlights points where a concentrated research effort may rapidly advance our understanding of both.

Morphostasis and immunity

Scientists have traditionally been resistant to fundamental changes in perspective. New ideas are rejected if they challenge essential, accepted paradigms. Here I present a concept that, I believe, represents a paradigm shift in the way self/non-self discrimination is perceived. Traditional opinion has it that lymphocytes carry out this discrimination. I propose an alternative view. Self/non-self discrimination is driven by mechanisms closely related to those that lead to cell sorting in disaggregated embryos. Lymphocytes are only used to classify cells according to their mode of death (apoptosis or necrosis). The hypothesis outlines the process of morphostasis (tissue homeostasis). It fills in much detail about the gradual evolution of the mammalian immune system. Earlier versions of this hypothesis have been reflexly rejected by numerous journals. Until recently, I too was unsure of the validity of the core concept. Recent publications have dispelled this doubt from my mind. A paradigm shift is due.

Evidence for a change in neurotransmitter affecting oesophageal motility in Parkinson's disease

In a study of oesophageal motility in 20 patients with Parkinson's disease, intravenous atropine produced marked disruption of co-ordination in response to swallows, when compared with control subjects. This suggests that cholinergic rather than dopaminergic mechanisms are more important in the control of swallowing in patients with Parkinsonism. No conclusive evidence of peripheral dopamine depletion or autonomic neuropathy was found, although minor changes suggestive of the former were found in severely affected patients.