Social histories of public health misinformation and infodemics: case studies of four pandemics

Recognition of misinformation as a public health threat and interest in infodemics, defined as an inundation of information accompanying an epidemic or acute health event, have increased worldwide. However, scientists have no consensus on how to best define and identify misinformation and other essential characteristics of infodemics. We conducted a narrative review of secondary historical sources to examine previous infodemics in relation to four infectious diseases associated with pandemics (ie, smallpox, cholera, 1918 influenza, and HIV) and challenge the assumption that misinformation is a new phenomenon associated with increased use of social media or with the COVID-19 pandemic. On the contrary, we found that the spread of health misinformation has always been a public health challenge that has necessitated innovative solutions from medical and public health communities. We suggest expanding beyond the narrow scope of addressing misinformation to manage information ecosystems, defined as how people consume, produce, interact with, and behave around information, which include factors such as trust, stigma, and scientific literacy. Although misinformation can spread on a global scale, this holistic approach advocates for community-level interventions that improve relationships and trust between medical or public health entities and local populations.

Beyond misinformation: developing a public health prevention framework for managing information ecosystems

The COVID-19 pandemic has highlighted how infodemics (defined as an overabundance of information, including misinformation and disinformation) pose a threat to public health and could hinder individuals from making informed health decisions. Although public health authorities and other stakeholders have implemented measures for managing infodemics, existing frameworks for infodemic management have been primarily focused on responding to acute health emergencies rather than integrated in routine service delivery. We review the evidence and propose a framework for infodemic management that encompasses upstream strategies and provides guidance on identifying different interventions, informed by the four levels of prevention in public health: primary, secondary, tertiary, and primordial prevention. On the basis of a narrative review of 54 documents (peer-reviewed and grey literature published from 1961 to 2023), we present examples of interventions that belong to each level of prevention. Adopting this framework requires proactive prevention and response through managing information ecosystems, beyond reacting to misinformation or disinformation.

Online medical student OSCE examinations during the first three years of the COVID-19 pandemic compared to three years pre-pandemic: An Australian experience in psychiatry and addiction medicine

PURPOSE

We have evaluated the final-year Psychiatry and Addiction Medicine (PAM) summative Objective Structured Clinical Examination (OSCE) examinations in a four-year graduate medical degree program, for the previous three years as a baseline comparator, and during three years of the COVID-19 pandemic (2020-2022).

METHODS

A de-identified analysis of medical student summative OSCE examination performance, and comparative review for the 3 years before, and for each year of the pandemic.

RESULTS

Internal reliability in test scores as measured by R-squared remained the same or increased following the start of the pandemic. There was a significant increase in mean test scores after the start of the pandemic compared to pre-pandemic for combined OSCE scores for all final-year disciplines, as well as for the PAM role-play OSCEs, but not for the PAM mental state examination OSCEs.

CONCLUSIONS

Changing to online OSCEs during the pandemic was related to an increase in scores for some but not all domains of the tests. This is in line with a nascent body of literature on medical teaching and examination following the start of the pandemic. Further research is needed to optimise teaching and examination in a post-pandemic medical school environment.

A Systematic Review Of COVID-19 Misinformation Interventions: Lessons Learned

Governments, public health authorities, and social media platforms have employed various measures to counter misinformation that emerged during the COVID-19 pandemic. The effectiveness of those misinformation interventions is poorly understood. We analyzed fifty papers published between January 1, 2020, and February 24, 2023, to understand which interventions, if any, were helpful in mitigating COVID-19 misinformation. We found evidence supporting accuracy prompts, debunks, media literacy tips, warning labels, and overlays in mitigating either the spread of or belief in COVID-19 misinformation. However, by mapping the different characteristics of each study, we found levels of variation that weaken the current evidence base. For example, only 18 percent of studies included public health-related measures, such as intent to vaccinate, and the misinformation that interventions were tested against ranged considerably from conspiracy theories (vaccines include microchips) to unproven claims (gargling with saltwater prevents COVID-19). To more clearly discern the impact of various interventions and make evidence actionable for public health, the field urgently needs to include more public health experts in intervention design and to develop a health misinformation typology; agreed-upon outcome measures; and more global, more longitudinal, more video-based, and more platform-diverse studies.

Measuring the Burden of Infodemics: Summary of the Methods and Results of the Fifth WHO Infodemic Management Conference

Background

An infodemic is excess information, including false or misleading information, that spreads in digital and physical environments during a public health emergency. The COVID-19 pandemic has been accompanied by an unprecedented global infodemic that has led to confusion about the benefits of medical and public health interventions, with substantial impact on risk-taking and health-seeking behaviors, eroding trust in health authorities and compromising the effectiveness of public health responses and policies. Standardized measures are needed to quantify the harmful impacts of the infodemic in a systematic and methodologically robust manner, as well as harmonizing highly divergent approaches currently explored for this purpose. This can serve as a foundation for a systematic, evidence-based approach to monitoring, identifying, and mitigating future infodemic harms in emergency preparedness and prevention.

Objective

In this paper, we summarize the Fifth World Health Organization (WHO) Infodemic Management Conference structure, proceedings, outcomes, and proposed actions seeking to identify the interdisciplinary approaches and frameworks needed to enable the measurement of the burden of infodemics.

Methods

An iterative human-centered design (HCD) approach and concept mapping were used to facilitate focused discussions and allow for the generation of actionable outcomes and recommendations. The discussions included 86 participants representing diverse scientific disciplines and health authorities from 28 countries across all WHO regions, along with observers from civil society and global public health-implementing partners. A thematic map capturing the concepts matching the key contributing factors to the public health burden of infodemics was used throughout the conference to frame and contextualize discussions. Five key areas for immediate action were identified.

Results

The 5 key areas for the development of metrics to assess the burden of infodemics and associated interventions included (1) developing standardized definitions and ensuring the adoption thereof; (2) improving the map of concepts influencing the burden of infodemics; (3) conducting a review of evidence, tools, and data sources; (4) setting up a technical working group; and (5) addressing immediate priorities for postpandemic recovery and resilience building. The summary report consolidated group input toward a common vocabulary with standardized terms, concepts, study designs, measures, and tools to estimate the burden of infodemics and the effectiveness of infodemic management interventions.

Conclusions

Standardizing measurement is the basis for documenting the burden of infodemics on health systems and population health during emergencies. Investment is needed into the development of practical, affordable, evidence-based, and systematic methods that are legally and ethically balanced for monitoring infodemics; generating diagnostics, infodemic insights, and recommendations; and developing interventions, action-oriented guidance, policies, support options, mechanisms, and tools for infodemic managers and emergency program managers.

How Americans encounter guns: Mixed methods content analysis of YouTube and internet search data

Firearm-related injury and death is a serious public health issue in the U.S. As more Americans consume news and media online, there is growing interest in using these channels to prevent firearm-related harms. Understanding the firearm-related narratives to which consumers are exposed is foundational to this work. This research used the browsing behavior of a representative sample of American adults to identify seven firearm-related content "ecosystems" (defined as naturally occurring networks of channels watched by the same users) on YouTube; we then described the demographics and internet search patterns of users affiliated with each ecosystem. Over the 9-month study period, 72,205 panelists had 16,803,075 person-video encounters with 7,274,093 videos. Among these, 282,419 were related to firearms. Using fast greedy clustering, we partitioned users and channel interactions into seven distinct channel-based content ecosystems that reached more than 1/1000 YouTube users per day. These ecosystems were diverse in reach, users, and content (e.g., guns for self-protection, guns for fun). On average, 0.5% of panelists performed a firearm-related internet search on a given day. The vast majority of searches were related to mass shootings or police-involved shootings (e.g., "active shooter"), and virtually none were about more common firearm harm such as suicide. Searches for firearm safety information were most common among panelists affiliated with the "Hunting & Fishing" and "Guns & Gear" ecosystems, which were watched primarily by older, white men. These findings identify an opportunity for analyzing firearm-related narratives and tailoring firearm safety messaging for users affiliated with specific online content ecosystems.

Final-year medical student Psychiatry and Addiction Medicine synchronous summative tele-assessments during a COVID-19 Delta-variant stay-at-home lockdown

OBJECTIVE

We describe the planning, process and evaluation of final-year Psychiatry and Addiction Medicine summative assessments in a four-year graduate medical degree program, during a COVID-19 Delta-variant public health stay-at-home lockdown.

CONCLUSIONS

We conducted separate written and clinical synchronous (real-time simultaneous) tele-assessments. We used online assessment technology with students, examiners and simulated patients, all in different physical locations. Medical students' examination performance showed a good range. This was comparable to other discipline stations, and performance in previous years. There was no differential performance of students through the day of the assessments.

WHO competency framework for health authorities and institutions to manage infodemics: its development and features

BACKGROUND

In April 2020, the World Health Organization (WHO) Information Network for Epidemics produced an agenda for managing the COVID-19 infodemic. "Infodemic" refers to the overabundance of information-including mis- and disinformation. In this agenda it was pointed out the need to create a competency framework for infodemic management (IM). This framework was released by WHO on 20th September 2021. This paper presents the WHO framework for IM by highlighting the different investigative steps behind its development.

METHODS

The framework was built through three steps. Step 1 included the preparatory work following the guidelines in the Guide to writing Competency Framework for WHO Academy courses. Step 2 was based on a qualitative study with participants (N = 25), identified worldwide on the basis of their academic background in relevant fields of IM or of their professional experience in IM activities at the institutional level. The interviews were conducted online between December 2020 and January 2021, they were video-recorded and analyzed using thematic analysis. In Step 3, two stakeholder panels were conducted to revise the framework.

RESULTS

The competency framework contains four primary domains, each of which comprised main activities, related tasks, and knowledge and skills. It identifies competencies to manage and monitor infodemics, to design, conduct and evaluate appropriate interventions, as well as to strengthen health systems. Its main purpose is to assist institutions in reinforcing their IM capacities and implementing effective IM processes and actions according to their individual contexts and resources.

CONCLUSION

The competency framework is not intended to be a regulatory document nor a training curriculum. As a WHO initiative, it serves as a reference tool to be applied according to local priorities and needs within the different countries. This framework can assist institutions in strengthening IM capacity by hiring, staff development, and human resources planning.

Conduct and evaluation of final-year medical student summative assessments in Psychiatry and Addiction Medicine during COVID-19: an Australian University Medical School experience

OBJECTIVE

To describe and share with the medical education community, the conduct and evaluation of summative graduate medical student assessments in Psychiatry and Addiction Medicine during COVID-19 at an Australian university.

METHODS

Summative assessments were redesigned as follows: written assessments were administered via an online platform (WATTLE), while the Objective Structured Clinical Examinations (OSCE) were conducted via a secure video-conferencing software (Zoom).

RESULTS

Our preliminary analysis of the summative assessments indicated that both examiners and students adapted to the format, with overall performance of the students showing no variation due to timing of the assessment (earlier versus later in the day) and performances similar to face-to-face assessments in previous years. Examiners also expressed positive feedback on the assessment process.

CONCLUSIONS

Our graduate fourth-year medical student summative assessments were effectively conducted using online and video-conferencing software in accordance with existing COVID-19 pandemic public health measures for physical distancing and hygiene.

A Public Health Research Agenda for Managing Infodemics: Methods and Results of the First WHO Infodemiology Conference

Background

An infodemic is an overflow of information of varying quality that surges across digital and physical environments during an acute public health event. It leads to confusion, risk-taking, and behaviors that can harm health and lead to erosion of trust in health authorities and public health responses. Owing to the global scale and high stakes of the health emergency, responding to the infodemic related to the pandemic is particularly urgent. Building on diverse research disciplines and expanding the discipline of infodemiology, more evidence-based interventions are needed to design infodemic management interventions and tools and implement them by health emergency responders.

Objective

The World Health Organization organized the first global infodemiology conference, entirely online, during June and July 2020, with a follow-up process from August to October 2020, to review current multidisciplinary evidence, interventions, and practices that can be applied to the COVID-19 infodemic response. This resulted in the creation of a public health research agenda for managing infodemics.

Methods

As part of the conference, a structured expert judgment synthesis method was used to formulate a public health research agenda. A total of 110 participants represented diverse scientific disciplines from over 35 countries and global public health implementing partners. The conference used a laddered discussion sprint methodology by rotating participant teams, and a managed follow-up process was used to assemble a research agenda based on the discussion and structured expert feedback. This resulted in a five-workstream frame of the research agenda for infodemic management and 166 suggested research questions. The participants then ranked the questions for feasibility and expected public health impact. The expert consensus was summarized in a public health research agenda that included a list of priority research questions.

Results

The public health research agenda for infodemic management has five workstreams: (1) measuring and continuously monitoring the impact of infodemics during health emergencies; (2) detecting signals and understanding the spread and risk of infodemics; (3) responding and deploying interventions that mitigate and protect against infodemics and their harmful effects; (4) evaluating infodemic interventions and strengthening the resilience of individuals and communities to infodemics; and (5) promoting the development, adaptation, and application of interventions and toolkits for infodemic management. Each workstream identifies research questions and highlights 49 high priority research questions.

Conclusions

Public health authorities need to develop, validate, implement, and adapt tools and interventions for managing infodemics in acute public health events in ways that are appropriate for their countries and contexts. Infodemiology provides a scientific foundation to make this possible. This research agenda proposes a structured framework for targeted investment for the scientific community, policy makers, implementing organizations, and other stakeholders to consider.

Use of a real-time microbial air sampler for operational cleanroom monitoring

A sampler that detects and counts viable particles in the air of cleanrooms in real-time was studied. It was found that when the sampler was used to monitor airborne particles dispersed from a number of materials used in cleanrooms, including garments, gloves, and skin, the number of viable particles dispersed from these materials was greater than anticipated. It was concluded that a substantial proportion of these viables were of a non-microbiological origin. When the sampler was used to monitor a non-unidirectional airflow cleanroom occupied by personnel wearing cleanroom garments, it was found that the airborne viable concentrations were unrealistically high and variable in comparison to microbe-carrying particles simultaneously measured with efficient microbial air samplers. These results confirmed previously reported ones obtained from a different real-time sampler. When the real-time sampler was used in a workstation within the same cleanroom, the recorded viables gave results that suggest that the sampler may provide an effective airborne monitoring method, but more investigations are required.

LAY ABSTRACT

The airborne concentrations measured by a real-time microbial air sampler within an operational, non-unidirectional airflow cleanroom were found to be unrealistically high due to a substantial numbers of particles of non-microbiological origin. These particles, which resulted in false-positive microbial counts, were found to be associated with a number of materials used in cleanrooms. When the sampler was used within a cleanroom workstation, the counts appeared to be more realistic and suggest that this type of real-time airborne microbial counter may provide a useful monitoring method in such workstations, but further investigations are required.

Comparative genomic hybridization and pathological findings in atypical teratoid/rhabdoid tumour of the central nervous system

The atypical teratoid/rhabdoid tumour (AT/RT) is an uncommon tumour of the central nervous system in children, characterized by the presence of a rhabdoid cell component associated with variable combinations of primitive neuroectodermal tumour, mesenchymal and epithelial differentiation. Immunohistochemistry reveals a complex pattern of antigen expression and cytogenetic studies have demonstrated losses from chromosome 22. We have performed comparative genomic hybridization (CGH) on paraffin-embedded material from three cases of AT/RT. Two cases showed losses from chromosome 22 associated with other chromosome imbalances including losses from 1p in both cases. The third case demonstrated a loss from 8p as the sole abnormality. While monosomy or deletion from chromosome 22 is a useful diagnostic marker for AT/RT, it is not present in all cases. The variation in cytogenetic patterns reported for this tumour type raises the possibility that different genetic pathways may underlie this tumour phenotype and warrants the further definition of the cytogenetic spectrum for this rare tumour.

CD80-mediated induction of immunostimulation in two ocular melanoma cell lines is augmented by interferon-gamma

Although the transfection of the T-cell costimulatory molecule CD80 cDNA into human tumours can augment their immunogenicity in vitro, its expression alone is ineffective in many tumour systems. We evaluated the influence of CD80 expression on the immunostimulatory activity of ocular melanoma cell lines and determined whether IFN-gamma could enhance the effect. Two ocular melanoma cell lines were transfected with CD80 cDNA. The immunostimulatory capacity of the CD80+ transfectants was determined by their ability to stimulate the proliferation of allogeneic peripheral blood mononuclear cells (PBMC). The influence of additional accessory molecules on PBMC proliferation was assessed by pre-treating the CD80 transfectants with IFN-gamma. The CD80+ transfectants induced proliferation of allogeneic PBMC. IFN-gamma treatment of the tumour cells induced upregulated expression of MHC class I, de novo expression of MHC class II and CD54, and enhanced the ability of the CD80+ transfectants to stimulate PBMC proliferation. CD4+ T cells were not required for the proliferative response against untreated CD80+ tumour cells but were necessary for the augmentation of proliferation observed following IFN-gamma treatment. CD80+ ocular melanoma cells possess immunostimulatory potential which is augmented by IFN-gamma induced upregulation of cell surface molecules. Further studies on the role of costimulatory molecules in inducing anti-tumour immunity in ocular melanoma may help to define new strategies for application of immunotherapeutic approaches to treat this aggressive disease.

Influence of selenium supplements on the post-traumatic alterations of the thyroid axis: a placebo-controlled trial

OBJECTIVE

To investigate whether early selenium (Se) supplementation can modify the post-traumatic alterations of thyroid hormone metabolism, since the first week after trauma is characterised by low plasma Se and negative Se balances.

DESIGN

Prospective, placebo-controlled randomised supplementation trial.

SETTING

Surgical ICU in a tertiary university hospital.

PATIENTS

Thirty-one critically ill trauma patients aged 42 +/- 16 years (mean +/- SD), with severe multiple injury (Injury Severity Score 30 +/- 7).

INTERVENTION

Supplementation during the first 5 days after injury with either Se or placebo. The selenium group was further randomised to receive daily 500 microg Se, with or without 150 mg alpha-tocopherol (AT) and 13 mg zinc supplements. The placebo group received the vehicle. Circulating Se, AT, zinc, and thyroid hormones were determined on D0 (= day 0, admission), D1, D2, D5, D10, and D20.

RESULTS

Plasma Se, low on D0, normalised from D1 in the selenium group; total T4 and T3 increased more and faster after D2 (P = 0.04 and 0.08), reverse T3 rising less between D0 and D2 (P = 0.05).

CONCLUSIONS

Selenium supplements increased the circulating Se levels. Supplementation was associated with modest changes in thyroid hormones, with an earlier normalisation of T4 and reverse T3 plasma levels. The addition of AT and zinc did not produce any additional change.

Trace element supplementation modulates pulmonary infection rates after major burns: a double-blind, placebo-controlled trial

Infections remain the leading cause of death after major burns. Trace elements are involved in immunity and burn patients suffer acute trace element depletion after injury. In a previous nonrandomized study, trace element supplementation was associated with increased leukocyte counts and shortened hospital stays. This randomized, placebo-controlled trial studied clinical and immune effects of trace element supplements. Twenty patients, aged 40 +/- 16 y (mean +/- SD), burned on 48 +/- 17% of their body surfaces, were studied for 30 d after injury. They consumed either standard trace element intakes plus supplements (40.4 micromol Cu, 2.9 micromol Se, and 406 micromol Zn; group TE) or standard trace element intakes plus placebo (20 micromol Cu, 0.4 micromol Se, and 100 micromol Zn; group C) for 8 d. Demographic data were similar for both groups. Mean plasma copper and zinc concentrations were below normal until days 20 and 15, respectively (NS). Plasma selenium remained normal for group TE but decreased for group C (P < 0.05 on days 1 and 5). Total leukocyte counts tended to be higher in group TE because of higher neutrophil counts. Proliferation to mitogens was depressed compared with healthy control subjects (NS). The number of infections per patient was significantly (P < 0.05) lower in group TE (1.9 +/- 0.9) than in group C (3.1 +/- 1.1) because of fewer pulmonary infections. Early trace element supplementation appears beneficial after major burns; it was associated with a significant decrease in the number of bronchopneumonia infections and with a shorter hospital stay when data were normalized for burn size.

A search for immunoglobulins inhibiting gonadal cell steroidogenesis in premature ovarian failure

Premature ovarian failure (POF) may be caused by the action of circulating gonadotrophin receptor-blocking antibodies. Luteinizing hormone (LH)-stimulated testosterone production from mouse Leydig cells and follicle stimulating hormone (FSH)-stimulated oestradiol production from immature rat Sertoli cells were therefore studied in the presence of protein-G purified immunoglobulin G (IgG) samples from control subjects (n = 9), infertile women with elevated early follicular phase FSH levels but otherwise normal menstrual cycles (n = 10), and patients with POF (n = 10) or Graves' disease (n = 10). A saturating and subsaturating (78% for LH; 60% for FSH) dose of each hormone was chosen for study. A commercial preparation of human IgG (Sigma IgG, 0.75 mg/ml) employed as negative control had no effect on basal or gonadotrophin-stimulated steroidogenesis. In its presence, saturating doses of LH (2 IU/l) and FSH (20 IU/l) gave rise to 11.2 +/- 0.8 (n = 7) and 25.1 +/- 5.8 (n = 8) fold increases in steroid secretion. IgG (0.75 mg/ml) had no effect in the four groups on LH-stimulated testosterone outputs using a saturating (2 IU/l) or subsaturating (1 IU/l) dose of hormone. For example, LH (2 IU/l)-stimulated testosterone production was 94% (83-96 median; interquartile range) and 88% (81-99) of the Sigma IgG control for control and POF groups respectively. However, four out of nine IgG samples from the normal subjects (mean +/- SEM = 86 +/- 6%), two out of 10 of the high FSH group (77 +/- 4%), five out of 10 with Graves' disease (86 +/- 3%) and six out of 10 with POF (76 +/- 6%) gave rise to LH (2 IU/l)-stimulated testosterone outputs which were lower (P < 0.05) than that of Sigma IgG control. Using the identical set of patients and an IgG concentration of 0.25 mg/ml, the FSH-stimulated oestradiol outputs of the four groups were similar when using either the saturating (20 IU/l) or subsaturating (5 IU/l) dose of the hormone. Thus, the percentage of FSH (20 IU/l)-stimulated oestradiol production of the Sigma IgG control was 81 (66-89 median, interquartile range) and 50 (38-84) for control and POF groups respectively. However, once again individual patients had inhibitory IgGs such that four out of nine (controls), three out of 10 (high FSH group), four out of 10 (Graves' disease) and six out of 10 (POF patients) inhibited (P < 0.05) FSH (20 IU/l)-stimulated oestradiol secretion by 52 +/- 9 (mean +/- SEM), 44 +/- 7, 52 +/- 6 and 41 +/- 6% respectively. Of the patients with inhibitory IgGs the extent of inhibition of gonadotrophin-stimulated steroid secretion was similar between the groups. In conclusion, there is little evidence to suggest that immunoglobulins blocking gonadotrophin receptors are a mechanism for POF in a large proportion of women suffering from this condition.

In-vitro biopotency and glycoform distribution of recombinant human follicle stimulating hormone (Org 32489), Metrodin and Metrodin-HP

In this study the in-vitro biopotency and glycoform distribution of human recombinant follicle stimulating hormone (FSH, Org 32489) has been assessed. The biopotency of recombinant FSH was studied using animal (rat Sertoli) and human (granulosa-lutein) cell models. Recombinant FSH, as measured in the rat Sertoli cell assay, was more potent than the urinary preparations Metrodin, Metrodin-HP and IS 70/45 with half maximal stimulation (ED50; mean +/- SEM, n > 3) occurring at 2.2 +/- 0.5 IU/I (recombinant FSH), 4.7 +/- 1.1 IU/I (Metrodin), 13.2 +/- 0.7 IU/I (Metrodin-HP) and 6.4 +/- 0.3 IU/I (IS 70/45); the pituitary preparation IRP 83/575 had an ED50 of 10.4 +/- 0.1 IU/I. Using human granulosa-lutein cells, cultured for up to 4 days in the absence of exogenous steroid precursors, recombinant FSH was either without effect (three out of five patients) or inhibited both oestradiol and progesterone secretion. FSH (83/575) was without effect on oestradiol with preparations from any of the patients but slightly stimulated (134 +/- 8%; mean +/- SEM, P < 0.05) progesterone production at the highest dose (80 IU/I). The distribution of FSH isoforms, assessed by polyclonal radioimmunoassay, following chromatofocusing over the ranges pH < 3.5 and pH 3.5-7.0 respectively was recombinant FSH, 12.4 and 87.6%; Metrodin, 19.8 and 80.2%; Metrodin-HP, 50.2 and 49.8%; IS 70/45, 15.0 and 85.0%; IS 83/575, 70.9 and 29.1%. All glycoforms were pI < 7.0 for the five preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Tuning in to fish swimming waves: body form, swimming mode and muscle function

Most fish species swim with lateral body undulations running from head to tail. These waves run more slowly than the waves of muscle activation causing them, reflecting the effect of the interaction between the fish's body and the reactive forces from the water. The coupling between both waves depends on the lateral body shape and on the mechanical properties of the tail. During steady swimming, the length of each myotomal muscle fibre varies cyclically. The phase relationship between the strain (muscle length change) cycle and the active period (when force is generated) determines the work output of the muscle. The muscle power is converted to thrust either directly by the bending body or almost exclusively by the tail, depending upon the body shape of the species and the swimming kinematics. We have compared the kinematics and muscle activity patterns from seven species of fish with different body forms and swimming modes and propose a model which yields a consistent pattern, with at least three extremes. Subtle tuning of the phase relationship between muscle strain and activation cycles can lead to major changes in the way muscles function in different swimming modes.