- Email: [email protected]
Sometimes Scientists Get the Flu. Wrong…!
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Forum
articles and public information resources, and this is where problems may arise. Misuse of basic definitions, for example the incorrect use of the word ‘disease’, as opposed to rightly referring to the pathogen in expressions such as ‘disease transmission’, ‘vector of disease’, ‘vector-borne disease’, ‘disease spillover’, and ‘disease reservoir’ are frequent in the scientific literature (Figure 1). Confusion caused by interchanging the name for the pathogen with ‘disease’ may be exacerbated when a single pathogen can manifest as multiple diseases; for example, the In Italian you can ‘pass a fever’ between West Nile virus can cause the West Nile one another, in English we say ‘to catch a fever, West Nile encephalitis, and West cold’, and in French you can also ‘get the Nile meningitis in humans [1]. flu’. While we do not intend to criticise these harmless colloquialisms, errors in The incorrect use of definitions in epidereference to the use of ‘pathogen’ and miology may have unconscious roots ‘disease’ are numerous in scientific deep in the pre-scientific culture, when a
humans, bluetongue virus in livestock, as well as the fungi which can cause white nose syndrome and ash dieback disease in wildlife and plants respectively. In order for scientists who study pathogens and/or disease to collaborate and disseminate information to the public, it is vital that 1,2,4 Matteo Marcantonio, communication on this topic is accurate Emily L. Pascoe,1,3,* and and the proper terminology is used. Here Frédéric Baldacchino1 we aim to highlight the significance of using appropriate terminology and indicate the In an international research envi- correct use of some fundamental expresronment, accurate communication sions in epidemiology.
Sometimes Scientists Get the Flu. Wrong. . .!
is vital. However, the scientific literature does not always utilise consistent terminology and the misuse of some expressions in epidemiology is rife. We encourage the correct terms to be used appropriately to avoid confusion between scientists, policy makers, and members of the public.
Box 1. Definitions in Epidemiology
An Italian man, an English woman, and a French man walk into a lab. It sounds like the start of a joke, but this is in fact the everyday reality of our research group. To bridge the language gap we use English as a common language in the professional research environment. However, words can still get lost in translation, and to ensure that we do not mistakenly exchange information in a misleading manner, we are careful to use the correct scientific terminology. In doing so, we can effectively collaborate and integrate our research on human, domestic animal, and wildlife epidemiology. Epidemiology includes the study of both pathogens and the diseases they cause, which are two interconnected yet very different aspects of this topic. A ‘pathogen’ is an infectious agent, which, when transmitted to a host, can result in an asymptomatic infection, or can manifest within the host as specific symptoms – the ‘disease’ (Box 1). Epidemiology continues to receive substantial interest due to the emergence or re-emergence of pathogens that can cause significant impacts on health, biodiversity, and economy, such as the West Nile and Zika viruses and HIV in
Disease: any abnormal condition in which the cells in the body are damaged and symptoms of illness begin to appear. An infectious disease is an illness caused by a pathogen, including viruses, bacteria, fungi, protozoa, ‘macroparasites’ (see definition for parasite below), or abnormal proteins known as prions. A noninfectious disease is an illness that is not caused by an infectious pathogen (e.g., diabetes, canceriii). Host: an organism on or within which another organism lives. Interactions between the two organisms can result in damage, benefit, or indifference to the host, and thus in the states of symbiosis, colonisation, commensalism, latency, or disease [5]. Parasite: an organism that benefits from, whilst having negative impacts on, its host. ‘Microparasites’ (viruses, bacteria, fungi, and protozoans) are distinguished from ‘macroparasites’ (helminths, arthropods, and other metazoans [6]). Pathogen: a biological agent that causes disease. Emerging pathogens are defined as whose incidence is increasing following its first introduction into a new host population, and re-emerging pathogens as those whose incidence is increasing in an existing host population as a result of long-term changes in its underlying epidemiology [7]. Reservoir: an organism within which a parasite that is pathogenic to another organism may live and reproduce, without harming it. A reservoir is an ecological system in which a pathogen survives indefinitely [8]. Spillover: pathogen spillover occurs when epidemics in a host population are driven not by transmission within that population, but by transmission from a reservoir population [9]. Transmission: the major categories of transmission route of pathogens are: (i) direct contact (including inhalation, via wounds, sexual contact, transmission in utero, and iatrogenic transmission); (ii) indirect contact (via food or an environmental reservoir, including free-living infective stages); and (iii) vector-borne (biting or mechanical transmission by a vector). Transmission of many pathogens can fall within more than one of these categories [7]. Vector: an organism that carries an infectious agent from [6_TD$IF]one organism to another. A vector is often any intermediate host or physical entity that transmits a parasite to the definitive host, including arthropods that transmit parasites by deposition or injection and prey that transmits the parasite when ingested[7_TD$IF] by the predator [10].
Trends in Parasitology, Month Year, Vol. xx, No. yy
1
TREPAR 1570 No. of Pages 3
Web of science records
400
200
0 1980
1990
2000
2010
Year Key:
Transmission and disease
Vector and disease
Figure 1. The Trend [4_TD$IF]of Two Misused Expressions [4_TD$IF]within Scientific Publications. A graphical representation of occurrence within scientific publications for two expressions that wrongly associate ‘transmission’ with ‘disease’ (red line, total of 5777 retrieved publications) or ‘vector’ with ‘disease’ (blue line, total of 3211 retrieved publications). Two searches were performed in Web of ScienceTM, one for the following incorrect expressions: TOPIC: (“vector of disease” OR “vector of diseases” OR “vector of a disease” OR “disease vector” OR “vector borne disease” OR “vector-borne disease*”) and the other for TOPIC: (“disease transmission” OR “diseases transmission” OR “transmission of a disease” OR “transmission of diseases” NOT “transmission of disease agents” NOT “transmission of a disease agent”) between the years 1970 and 2015. For each search result the number of publications retrieved per year of publication was extracted to produce the plot.
disease was wrongly considered to be caused by ‘bad air’, and thus it was believed that the disease itself was ‘transmissible’ (miasmatic theory of disease propagation). We find heritage of this belief in the etymology of disease names such as ‘malaria’ which originates from the Italian ‘mal’aria’ - ‘bad air’. Only since the 18th century, thanks to discoveries such as ‘animalcules’ by van Leeuwenhoek (1760s), the antispontaneous generation experiments by Pasteur (1860s) and the definition of Koch's postulates (1890s), has a causative relationship between an
2
Trends in Parasitology, Month Year, Vol. xx, No. yy
in the scientific literature. A Web of ScienceTM search for incorrect expressions that combined the word ‘disease’ with ‘transmission’ or ‘vector’ retrieved 517 and 445 articles respectively that had been published in 2015 alone (Figure 1). Surprisingly, even the organisations leading pathogen and disease research and control strategies have perpetuated the misuse of terminology. The World Health Organization (WHO) describes vectors as ‘organisms that can transmit infectious diseases’i[8_TD$IF] and the CDC states that ‘there are no reports of Lyme disease transmission from breast milk’ii. With these, and many other well-trusted organisations misusing such phrases, it is unsurprising that the rest of the scientific community follows suit. One could argue that the priority of WHO and CDC is to inform the public, to whom the word ‘disease’ may evoke stronger interest and a more positive response to public health programmes than ‘pathogen’, which many people may not associate with health risks. However, as scientists it is our duty to provide factual information which is accessible to all, not a variation of the truth that is more digestible. Consequently the incorrect use of terminology has inevitably led to confusion amongst those of us in science, particularly for non-native speakers and those new to the field. Furthermore, it may be misleading for members of the public, and for the policy makers using these important publications to inform policies that aim [10_TD$IF]to [1_TD$IF]limit the spread of vectors, the pathogens they carry, or the diseases that may potentially ensue. It has been acknowledged that policies [12_TD$IF]that [13_TD$IF]aim [14_TD$IF]to control pathogens and diseases are currently fragmented and thus inefficient [3], and we propose that one fundamental step towards a more unified and global approach to pathogen and disease control could be to utilise consistent terminology. As such, it is important that we remind ourselves of the correct definitions in epidemiology (Box 1).
agent (pathogen) and a subsequent disease been defined (the germ theory of disease). However, abandoning the miasmatic theory has been a slow process. For instance, in the 19th century it was still widely believed that the yellow fever (YF) disease was disseminated in the air, and evidence was not found until the beginning of the 20th century that, in fact, YF is caused by a virus vectored by Aedes aegypti mosquitoes [2]. The relationship between a disease and the causative pathogen is now well acknowledged, yet Science is[2_TD$IF] a refinement of the way we misleading terms are still commonly used think every day [4], and this implies that
TREPAR 1570 No. of Pages 3
we must also refine the ambiguities of our everyday language for it to be effectively communicated. Indeed, science is of limited value unless it is accessible to everybody, thus terminology must be understandable, accurate, and consistent. We urge that care is taken when communicating scientific research, particularly in relation to pathogens and diseases. Thus, here we aim to remind researchers of the correct terminology in epidemiology and propose that scientists should lead the way in utilising these terms correctly. [15_TD$IF]By [16_TD$IF]contrast, if we do insist on using ‘pathogen’ and ‘disease’ interchangeably, we suggest that their formal definitions should be reconsidered to clarify any misconceptions. We hope that by drawing attention to more careful usage of these terms we can
make the invaluable research on emerging and re-emerging pathogens less ambiguous and understandable to all. There is nothing wrong with catching a cold from a friend, but science will not find a cure for this! Resources i
[9_TD$IF] http://www.who.int/mediacentre/factsheets/fs387/
en/ ii
http://www.cdc.gov/lyme/transmission/
iii
http://needtoknow.nas.edu/id/glossary/
*Correspondence: [email protected] (E.L. Pascoe). http://dx.doi.org/10.1016/j.pt.2016.10.005 References 1. Campbell, G.L. et al. (2002) West Nile virus. Lancet Infect. Dis. 2, 519–529 2. Marchoux, E. and Simond, P-L. (1906) Etudes sur la fièvre jaune. Ann. I. Pasteur Paris. 20, 16–40 (in French) 3. Dunn, A.M. and Hatcher, M.J. (2015) Parasites and biological invasions: parallels, interactions, and control. Trends Parasitol. 31, 189–199 4. Einstein, A. (1936) Physics and reality. J. Frankl. Inst. 221, 349–382 5. Casadevall, A. and Pirofski, L. (2015) What is a host? Incorporating the microbiota into the damage-response framework. Infect. Immun. 83, 2–7
Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all’Adige (TN), Italy 2 Geoinformation in Environmental Planning Lab,
6. Anderson, R.M. and May, R.M. (1979) Population biology of infectious diseases: Part I. Nature 280, 361–367
Technische Universität Berlin, Germany School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AX, UK 4 Current address: Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis
8. Ashford, R.W. (2003) When is a reservoir not a reservoir? Emerg. Infect. Dis. 9, 1495–1496
1
3
7. Woolhouse, M.E.J. (2002) Population biology of emerging and re-emerging pathogens. Trends Microbiol. 10, S3–S7
9. Power, A.G. and Mitchell, C.E. (2004) Pathogen spillover in disease epidemics. Am. Nat. 164, S79–S89 10. Combes, C. (2001) Parasitism: The Ecology and Evolution of Intimate Interactions, University of Chicago Press
Trends in Parasitology, Month Year, Vol. xx, No. yy
3
Forum
articles and public information resources, and this is where problems may arise. Misuse of basic definitions, for example the incorrect use of the word ‘disease’, as opposed to rightly referring to the pathogen in expressions such as ‘disease transmission’, ‘vector of disease’, ‘vector-borne disease’, ‘disease spillover’, and ‘disease reservoir’ are frequent in the scientific literature (Figure 1). Confusion caused by interchanging the name for the pathogen with ‘disease’ may be exacerbated when a single pathogen can manifest as multiple diseases; for example, the In Italian you can ‘pass a fever’ between West Nile virus can cause the West Nile one another, in English we say ‘to catch a fever, West Nile encephalitis, and West cold’, and in French you can also ‘get the Nile meningitis in humans [1]. flu’. While we do not intend to criticise these harmless colloquialisms, errors in The incorrect use of definitions in epidereference to the use of ‘pathogen’ and miology may have unconscious roots ‘disease’ are numerous in scientific deep in the pre-scientific culture, when a
humans, bluetongue virus in livestock, as well as the fungi which can cause white nose syndrome and ash dieback disease in wildlife and plants respectively. In order for scientists who study pathogens and/or disease to collaborate and disseminate information to the public, it is vital that 1,2,4 Matteo Marcantonio, communication on this topic is accurate Emily L. Pascoe,1,3,* and and the proper terminology is used. Here Frédéric Baldacchino1 we aim to highlight the significance of using appropriate terminology and indicate the In an international research envi- correct use of some fundamental expresronment, accurate communication sions in epidemiology.
Sometimes Scientists Get the Flu. Wrong. . .!
is vital. However, the scientific literature does not always utilise consistent terminology and the misuse of some expressions in epidemiology is rife. We encourage the correct terms to be used appropriately to avoid confusion between scientists, policy makers, and members of the public.
Box 1. Definitions in Epidemiology
An Italian man, an English woman, and a French man walk into a lab. It sounds like the start of a joke, but this is in fact the everyday reality of our research group. To bridge the language gap we use English as a common language in the professional research environment. However, words can still get lost in translation, and to ensure that we do not mistakenly exchange information in a misleading manner, we are careful to use the correct scientific terminology. In doing so, we can effectively collaborate and integrate our research on human, domestic animal, and wildlife epidemiology. Epidemiology includes the study of both pathogens and the diseases they cause, which are two interconnected yet very different aspects of this topic. A ‘pathogen’ is an infectious agent, which, when transmitted to a host, can result in an asymptomatic infection, or can manifest within the host as specific symptoms – the ‘disease’ (Box 1). Epidemiology continues to receive substantial interest due to the emergence or re-emergence of pathogens that can cause significant impacts on health, biodiversity, and economy, such as the West Nile and Zika viruses and HIV in
Disease: any abnormal condition in which the cells in the body are damaged and symptoms of illness begin to appear. An infectious disease is an illness caused by a pathogen, including viruses, bacteria, fungi, protozoa, ‘macroparasites’ (see definition for parasite below), or abnormal proteins known as prions. A noninfectious disease is an illness that is not caused by an infectious pathogen (e.g., diabetes, canceriii). Host: an organism on or within which another organism lives. Interactions between the two organisms can result in damage, benefit, or indifference to the host, and thus in the states of symbiosis, colonisation, commensalism, latency, or disease [5]. Parasite: an organism that benefits from, whilst having negative impacts on, its host. ‘Microparasites’ (viruses, bacteria, fungi, and protozoans) are distinguished from ‘macroparasites’ (helminths, arthropods, and other metazoans [6]). Pathogen: a biological agent that causes disease. Emerging pathogens are defined as whose incidence is increasing following its first introduction into a new host population, and re-emerging pathogens as those whose incidence is increasing in an existing host population as a result of long-term changes in its underlying epidemiology [7]. Reservoir: an organism within which a parasite that is pathogenic to another organism may live and reproduce, without harming it. A reservoir is an ecological system in which a pathogen survives indefinitely [8]. Spillover: pathogen spillover occurs when epidemics in a host population are driven not by transmission within that population, but by transmission from a reservoir population [9]. Transmission: the major categories of transmission route of pathogens are: (i) direct contact (including inhalation, via wounds, sexual contact, transmission in utero, and iatrogenic transmission); (ii) indirect contact (via food or an environmental reservoir, including free-living infective stages); and (iii) vector-borne (biting or mechanical transmission by a vector). Transmission of many pathogens can fall within more than one of these categories [7]. Vector: an organism that carries an infectious agent from [6_TD$IF]one organism to another. A vector is often any intermediate host or physical entity that transmits a parasite to the definitive host, including arthropods that transmit parasites by deposition or injection and prey that transmits the parasite when ingested[7_TD$IF] by the predator [10].
Trends in Parasitology, Month Year, Vol. xx, No. yy
1
TREPAR 1570 No. of Pages 3
Web of science records
400
200
0 1980
1990
2000
2010
Year Key:
Transmission and disease
Vector and disease
Figure 1. The Trend [4_TD$IF]of Two Misused Expressions [4_TD$IF]within Scientific Publications. A graphical representation of occurrence within scientific publications for two expressions that wrongly associate ‘transmission’ with ‘disease’ (red line, total of 5777 retrieved publications) or ‘vector’ with ‘disease’ (blue line, total of 3211 retrieved publications). Two searches were performed in Web of ScienceTM, one for the following incorrect expressions: TOPIC: (“vector of disease” OR “vector of diseases” OR “vector of a disease” OR “disease vector” OR “vector borne disease” OR “vector-borne disease*”) and the other for TOPIC: (“disease transmission” OR “diseases transmission” OR “transmission of a disease” OR “transmission of diseases” NOT “transmission of disease agents” NOT “transmission of a disease agent”) between the years 1970 and 2015. For each search result the number of publications retrieved per year of publication was extracted to produce the plot.
disease was wrongly considered to be caused by ‘bad air’, and thus it was believed that the disease itself was ‘transmissible’ (miasmatic theory of disease propagation). We find heritage of this belief in the etymology of disease names such as ‘malaria’ which originates from the Italian ‘mal’aria’ - ‘bad air’. Only since the 18th century, thanks to discoveries such as ‘animalcules’ by van Leeuwenhoek (1760s), the antispontaneous generation experiments by Pasteur (1860s) and the definition of Koch's postulates (1890s), has a causative relationship between an
2
Trends in Parasitology, Month Year, Vol. xx, No. yy
in the scientific literature. A Web of ScienceTM search for incorrect expressions that combined the word ‘disease’ with ‘transmission’ or ‘vector’ retrieved 517 and 445 articles respectively that had been published in 2015 alone (Figure 1). Surprisingly, even the organisations leading pathogen and disease research and control strategies have perpetuated the misuse of terminology. The World Health Organization (WHO) describes vectors as ‘organisms that can transmit infectious diseases’i[8_TD$IF] and the CDC states that ‘there are no reports of Lyme disease transmission from breast milk’ii. With these, and many other well-trusted organisations misusing such phrases, it is unsurprising that the rest of the scientific community follows suit. One could argue that the priority of WHO and CDC is to inform the public, to whom the word ‘disease’ may evoke stronger interest and a more positive response to public health programmes than ‘pathogen’, which many people may not associate with health risks. However, as scientists it is our duty to provide factual information which is accessible to all, not a variation of the truth that is more digestible. Consequently the incorrect use of terminology has inevitably led to confusion amongst those of us in science, particularly for non-native speakers and those new to the field. Furthermore, it may be misleading for members of the public, and for the policy makers using these important publications to inform policies that aim [10_TD$IF]to [1_TD$IF]limit the spread of vectors, the pathogens they carry, or the diseases that may potentially ensue. It has been acknowledged that policies [12_TD$IF]that [13_TD$IF]aim [14_TD$IF]to control pathogens and diseases are currently fragmented and thus inefficient [3], and we propose that one fundamental step towards a more unified and global approach to pathogen and disease control could be to utilise consistent terminology. As such, it is important that we remind ourselves of the correct definitions in epidemiology (Box 1).
agent (pathogen) and a subsequent disease been defined (the germ theory of disease). However, abandoning the miasmatic theory has been a slow process. For instance, in the 19th century it was still widely believed that the yellow fever (YF) disease was disseminated in the air, and evidence was not found until the beginning of the 20th century that, in fact, YF is caused by a virus vectored by Aedes aegypti mosquitoes [2]. The relationship between a disease and the causative pathogen is now well acknowledged, yet Science is[2_TD$IF] a refinement of the way we misleading terms are still commonly used think every day [4], and this implies that
TREPAR 1570 No. of Pages 3
we must also refine the ambiguities of our everyday language for it to be effectively communicated. Indeed, science is of limited value unless it is accessible to everybody, thus terminology must be understandable, accurate, and consistent. We urge that care is taken when communicating scientific research, particularly in relation to pathogens and diseases. Thus, here we aim to remind researchers of the correct terminology in epidemiology and propose that scientists should lead the way in utilising these terms correctly. [15_TD$IF]By [16_TD$IF]contrast, if we do insist on using ‘pathogen’ and ‘disease’ interchangeably, we suggest that their formal definitions should be reconsidered to clarify any misconceptions. We hope that by drawing attention to more careful usage of these terms we can
make the invaluable research on emerging and re-emerging pathogens less ambiguous and understandable to all. There is nothing wrong with catching a cold from a friend, but science will not find a cure for this! Resources i
[9_TD$IF] http://www.who.int/mediacentre/factsheets/fs387/
en/ ii
http://www.cdc.gov/lyme/transmission/
iii
http://needtoknow.nas.edu/id/glossary/
*Correspondence: [email protected] (E.L. Pascoe). http://dx.doi.org/10.1016/j.pt.2016.10.005 References 1. Campbell, G.L. et al. (2002) West Nile virus. Lancet Infect. Dis. 2, 519–529 2. Marchoux, E. and Simond, P-L. (1906) Etudes sur la fièvre jaune. Ann. I. Pasteur Paris. 20, 16–40 (in French) 3. Dunn, A.M. and Hatcher, M.J. (2015) Parasites and biological invasions: parallels, interactions, and control. Trends Parasitol. 31, 189–199 4. Einstein, A. (1936) Physics and reality. J. Frankl. Inst. 221, 349–382 5. Casadevall, A. and Pirofski, L. (2015) What is a host? Incorporating the microbiota into the damage-response framework. Infect. Immun. 83, 2–7
Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all’Adige (TN), Italy 2 Geoinformation in Environmental Planning Lab,
6. Anderson, R.M. and May, R.M. (1979) Population biology of infectious diseases: Part I. Nature 280, 361–367
Technische Universität Berlin, Germany School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AX, UK 4 Current address: Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis
8. Ashford, R.W. (2003) When is a reservoir not a reservoir? Emerg. Infect. Dis. 9, 1495–1496
1
3
7. Woolhouse, M.E.J. (2002) Population biology of emerging and re-emerging pathogens. Trends Microbiol. 10, S3–S7
9. Power, A.G. and Mitchell, C.E. (2004) Pathogen spillover in disease epidemics. Am. Nat. 164, S79–S89 10. Combes, C. (2001) Parasitism: The Ecology and Evolution of Intimate Interactions, University of Chicago Press
Trends in Parasitology, Month Year, Vol. xx, No. yy
3