A hypothesis: the conjunction of soldiers, gas, pigs, ducks, geese and horses in Northern France during the Great War provided the conditions for the emergence of the “Spanish” influenza pandemic of 1918–1919

Lost Lessons of the 1918 Influenza: The 1920s Working Hypothesis, the Public Health Paradigm, and the Prevention of Deadly Pandemics

In standard historical accounts, the hyperlethal 1918 flu pandemic was inevitable once a novel influenza virus appeared. However, in the years following the pandemic, it was obvious to distinguished flu experts from around the world that social and environmental conditions interacted with infectious agents and could enhance the virulence of flu germs. On the basis of the timing and geographic pattern of the pandemic, they hypothesized that an "essential cause" of the pandemic's extraordinary lethality was the extreme, prolonged, and industrial-scale overcrowding of US soldiers in World War I, particularly on troopships. This literature synthesis considers research from history, public health, military medicine, veterinary science, molecular genetics, virology, immunology, and epidemiology. Arguments against the hypothesis do not provide disconfirming evidence. Overall, the findings are consistent with an immunologically similar virus varying in virulence in response to war-related conditions. The enhancement-of-virulence hypothesis deserves to be included in the history of the pandemic and the war. These lost lessons of 1918 point to possibilities for blocking the transformation of innocuous infections into deadly disasters and are relevant beyond influenza for diseases like COVID-19. (Am J Public Health. 2022;112(10):1454-1464. https://doi.org/10.2105/AJPH.2022.306976).

Influenza A Viruses and Zoonotic Events-Are We Creating Our Own Reservoirs?

Zoonotic infections of humans with influenza A viruses (IAVs) from animal reservoirs can result in severe disease in individuals and, in rare cases, lead to pandemic outbreaks; this is exemplified by numerous cases of human infection with avian IAVs (AIVs) and the 2009 swine influenza pandemic. In fact, zoonotic transmissions are strongly facilitated by manmade reservoirs that were created through the intensification and industrialization of livestock farming. This can be witnessed by the repeated introduction of IAVs from natural reservoirs of aquatic wild bird metapopulations into swine and poultry, and the accompanied emergence of partially- or fully-adapted human pathogenic viruses. On the other side, human adapted IAV have been (and still are) introduced into livestock by reverse zoonotic transmission. This link to manmade reservoirs was also observed before the 20th century, when horses seemed to have been an important reservoir for IAVs but lost relevance when the populations declined due to increasing industrialization. Therefore, to reduce zoonotic events, it is important to control the spread of IAV within these animal reservoirs, for example with efficient vaccination strategies, but also to critically surveil the different manmade reservoirs to evaluate the emergence of new IAV strains with pandemic potential.

Advances and insights in the diagnosis of viral infections

Viral infections are the most common among diseases that globally require around 60 percent of medical care. However, in the heat of the pandemic, there was a lack of medical equipment and inpatient facilities to provide all patients with viral infections. The detection of viral infections is possible in three general ways such as (i) direct virus detection, which is performed immediately 1-3 days after the infection, (ii) determination of antibodies against some virus proteins mainly observed during/after virus incubation period, (iii) detection of virus-induced disease when specific tissue changes in the organism. This review surveys some global pandemics from 1889 to 2020, virus types, which induced these pandemics, and symptoms of some viral diseases. Non-analytical methods such as radiology and microscopy also are overviewed. This review overlooks molecular analysis methods such as nucleic acid amplification, antibody-antigen complex determination, CRISPR-Cas system-based viral genome determination methods. Methods widely used in the certificated diagnostic laboratory for SARS-CoV-2, Influenza A, B, C, HIV, and other viruses during a viral pandemic are outlined. A comprehensive overview of molecular analytical methods has shown that the assay's sensitivity, accuracy, and suitability for virus detection depends on the choice of the number of regions in the viral open reading frame (ORF) genome sequence and the validity of the selected analytical method.

[Covid-19 and the 1918-1919 influenza: historical parallels, questions and answers]

The rise of the covid-19 pandemic has led to renewed interest in the 1918-1919 influenza in search of aspects that might help us understand the current situation, but also as an opportunity to re-evaluate the serious twentieth-century health crisis in light of what we are experiencing now. In this context and with that goal, this historical reflection shows the parallels that exist and the need for a realization that our model of society is undergoing a crisis and requires profound transformation.

Osteopathic manipulative treatment and the Spanish flu: a historical literature review

Context

The Spanish flu pandemic of 1918 was approached with a variety of management techniques available at that time, including osteopathic care in addition to standard medical care.

Objective

To analyze the osteopathic manipulative treatment (OMT) techniques used for the management of patients affected by the Spanish flu according to four themes: the principles and procedures used, frequency and length of OMT, reported side effects, and advice for patients.

Methods

A structured review of the literature was performed by hand-searching texts at the Museum of Osteopathic Medicine International Center for Osteopathic History in Kirksville, Missouri, and online via PubMed (National Library of Medicine), ScienceDirect (Elsevier), and Google Scholar (Google, Inc). The literature search was carried out between February and March 2020. Three keywords were selected from the medical subject headings database of the National Library of Medicine: manipulation, osteopathic; influenza pandemic, 1918-1919; epidemics. Articles were then reviewed for relevance by screening for articles published between 1900 and 1940 that contained at least 1 of the following keywords in their title: Spanish influenza, flu, epidemic, grippe, pneumonia, or osteopathic management/treatment. All articles that provided information about OMT and advice met the inclusion criteria. Articles that did not report descriptions of manipulative intervention were excluded.

Results

Our search yielded 63 articles: 23 from the hand-search and 40 from the electronic search. No electronic source was selected for the review because none met inclusion criteria. A total of 16 articles from the hand-searched set met inclusion criteria and were analyzed according to the four main themes stated in the objective. The range of OMT approaches reported to be administered to patients with Spanish flu suggests that early osteopathic physicians treated patients with this disease using OMT in addition to offering advice on healthy lifestyle behaviors.

Conclusion

Conclusions from this study are limited by the historical and descriptive nature of the data gathered, which lacked the rigor of modern-day scientific studies. However, this review could lead to future research inquiries on the effectiveness of these approaches. Osteopathic physicians and osteopaths should embrace their historical osteopathic heritage by continuing the work of our predecessors and combining their hands-on experience and osteopathic principles with modern medical treatment and rigorous scientific standards.

Incidence of acute rheumatic fever and rheumatic heart disease in Melbourne, Australia from 1937 to 2013

AIM

Acute rheumatic fever (ARF) most commonly presents in children aged 5-14 years old. Lifelong rheumatic heart disease (RHD) can result. This study investigated time trends in ARF and RHD using inpatient data from the Royal Children's Hospital, Melbourne (RCH).

METHODS

A retrospective cohort study covering the period 1937-2013 was conducted using records from RCH, a quaternary paediatric hospital in Melbourne, Victoria, Australia. Patient data were identified using RCH classification of diseases coding for ARF or RHD for years <1952. For the period 1952-1987, this system was used in addition to identifying International Classification of Disease (ICD) discharge codes that corresponded to ARF or RHD. From 1988-2013, only ICD codes were used to identify patient data. Descriptive epidemiological analyses were performed, including incidence rate calculations using historical census population denominator data. Analyses focussed on children in the peak age group.

RESULTS

Among children aged five to 14 years, a total of 4337 RCH admissions with ARF/RHD occurred for 3015 patients. A sharp decline in first ARF/RHD hospitalisations at RCH occurred from 1959, following a peak mean annual incidence rate during 1944-1947 of 40.1/100 000 children (95% confidence interval (CI): 36.6-43.9; P < 0.05). Over 1996-2013, the mean annual incidence rate was 1.6/100 000 (95% CI: 1.3-1.8) and reached 2.3/100 000 (95% CI: 1.3-3.7) in 2005.

CONCLUSION

The burden of ARF and RHD treated at RCH declined following the 1940s, mirroring changes seen in North America and Europe. Despite this, inpatient treatment for these conditions continued to be provided right up until the end of the study period.

The Impact of a Six-Year Climate Anomaly on the "Spanish Flu" Pandemic and WWI

The H1N1 "Spanish influenza" pandemic of 1918-1919 caused the highest known number of deaths recorded for a single pandemic in human history. Several theories have been offered to explain the virulence and spread of the disease, but the environmental context remains underexamined. In this study, we present a new environmental record from a European, Alpine ice core, showing a significant climate anomaly that affected the continent from 1914 to 1919. Incessant torrential rain and declining temperatures increased casualties in the battlefields of World War I (WWI), setting the stage for the spread of the pandemic at the end of the conflict. Multiple independent records of temperature, precipitation, and mortality corroborate these findings.

Spanish flu in Turin as told by historical autopsy reports

Spanish flu spread worldwide between 1918 and 1920 causing over 20 million deaths, exceeding even the number of deaths registered during the First World War (WWI). The main symptom of the disease was hemorrhagic tracheobronchitis, the onset of which was typically sudden and fatal. Young, healthy people died quickly. Despite the tragic impact of the disease on populations, already exhausted by the First World War, there is very little documentation. This was likely due to the severe censorship of the time. For this reason, autopsy reports can be a relevant source of information on the disease. Historical catalogues kept in Turin, where all autopsies were detailed, can be consulted. According to the “Regolamento di Polizia Mortuaria” dating back to 1892, autopsies were to be performed on all patients that died at home or in hospital. Therefore, autopsy reports showing the spread of diseases among the population can also help us obtain information about the spread of Spanish flu in Turin. While not documented, almost certainly the “Regolamento” was improperly implemented since just 45 cases of Spanish flu were reported, while deaths were most certainly daily and in their hundreds. According to autopsy reports, the first case occurred on 8th October 1918, although, the first official diagnosis is dated as being 24th November 1918. The records show that 18 people died during the first Italian pandemic wave. The second Italian pandemic wave seems to have been even more aggressive in Turin with 27 people having died between 8th January 1920 and 7th February 1920.

Novel Viruses, Zoonotic Infections, and Travel Health

Novel viruses and zoonotic infections pose global health risks.

Loose Ends in the Epidemiology of the 1918 Pandemic: Explaining the Extreme Mortality Risk in Young Adults

In the century since the 1918 influenza pandemic, insights have been sought to explain the pandemic's signature pattern of high death rates in young adults and low death rates in the elderly and infants. Our understanding of the origin and evolution of the pandemic has shifted considerably. We review evidence of the characteristic age-related pattern of death during the 1918 pandemic relative to the "original antigenic sin" hypothesis. We analyze age-stratified mortality data from Copenhagen around 1918 to identify break points associated with unusual death risk. Whereas infants had no meaningful risk elevation, death risk gradually increased, peaking for young adults 20-34 years of age before dropping sharply for adults ages 35-44 years, suggesting break points for birth cohorts around 1908 and 1878. Taken together with data from previous studies, there is strong evidence that those born before 1878 or after 1908 were not at increased risk of dying of 1918 pandemic influenza. Although the peak death risk coincided with the 1889-1892 pandemic, the 1908 and 1878 break points do not correspond with known pandemics. An increasing number of interdisciplinary studies covering fields such as virology, phylogenetics, death, and serology offer exciting insights into patterns and reasons for the unusual extreme 1918 pandemic mortality risk in young adults.

Age-Specific Excess Mortality Patterns During the 1918-1920 Influenza Pandemic in Madrid, Spain

Although much progress has been made to uncover age-specific mortality patterns of the 1918 influenza pandemic in populations around the world, more studies in different populations are needed to make sense of the heterogeneous death impact of this pandemic. We assessed the absolute and relative magnitudes of 3 pandemic waves in the city of Madrid, Spain, between 1918 and 1920, on the basis of age-specific all-cause and respiratory excess death rates. Excess death rates were estimated using a Serfling model with a parametric bootstrapping approach to calibrate baseline death levels with quantified uncertainty. Excess all-cause and pneumonia and influenza mortality rates were estimated for different pandemic waves and age groups. The youngest and oldest persons experienced the highest excess mortality rates, and young adults faced the highest standardized mortality risk. Waves differed in strength; the peak standardized mortality risk occurred during the herald wave in spring 1918, but the highest excess rates occurred during the fall and winter of 1918/1919. Little evidence was found to support a “W”-shaped, age-specific excess mortality curve. Acquired immunity may have tempered a protracted fall wave, but recrudescent waves following the initial 2 outbreaks heightened the total pandemic mortality impact.

The 1918 influenza pandemic in Montevideo: The southernmost capital city in the Americas

BACKGROUND

Few studies have addressed the impact and dynamics of the 1918-1919 influenza pandemic in temperate regions of South America.

OBJECTIVE

To identify key factors for influenza onset, spread, and mortality in Montevideo and Uruguay in 1918-1919.

METHODS

An analysis of official national records of the public health system of Uruguay was performed.

RESULTS

From November to December of 1918 (spring), a total of 131 deaths due to influenza occurred in Montevideo and a total of 296 deaths accounted from July to September of 1919 (winter) in the same city. The total deaths attributed to influenza in Uruguay in 1918 and 1919 were 926 and 1089, respectively. In contrast, the mean annual mortality attributed to influenza in Uruguay from 1908 to 1917 was 50.9. A pattern of age-shift in mortality in the two pandemic waves studied was observed.

CONCLUSIONS

The results of studies revealed that Montevideo was first hit by the devastating second wave of the pandemic of 1918, arriving Montevideo at the end of the spring of that year. The third wave arrived by July 1919, in the winter season, and in the capital city was as severe as the second one.

Back to the Future: Lessons Learned From the 1918 Influenza Pandemic

2018 marks the 100-year anniversary of the 1918 influenza pandemic, which killed ~50 million people worldwide. The severity of this pandemic resulted from a complex interplay between viral, host, and societal factors. Here, we review the viral, genetic and immune factors that contributed to the severity of the 1918 pandemic and discuss the implications for modern pandemic preparedness. We address unresolved questions of why the 1918 influenza H1N1 virus was more virulent than other influenza pandemics and why some people survived the 1918 pandemic and others succumbed to the infection. While current studies suggest that viral factors such as haemagglutinin and polymerase gene segments most likely contributed to a potent, dysregulated pro-inflammatory cytokine storm in victims of the pandemic, a shift in case-fatality for the 1918 pandemic toward young adults was most likely associated with the host's immune status. Lack of pre-existing virus-specific and/or cross-reactive antibodies and cellular immunity in children and young adults likely contributed to the high attack rate and rapid spread of the 1918 H1N1 virus. In contrast, lower mortality rate in in the older (>30 years) adult population points toward the beneficial effects of pre-existing cross-reactive immunity. In addition to the role of humoral and cellular immunity, there is a growing body of evidence to suggest that individual genetic differences, especially involving single-nucleotide polymorphisms (SNPs), contribute to differences in the severity of influenza virus infections. Co-infections with bacterial pathogens, and possibly measles and malaria, co-morbidities, malnutrition or obesity are also known to affect the severity of influenza disease, and likely influenced 1918 H1N1 disease severity and outcomes. Additionally, we also discuss the new challenges, such as changing population demographics, antibiotic resistance and climate change, which we will face in the context of any future influenza virus pandemic. In the last decade there has been a dramatic increase in the number of severe influenza virus strains entering the human population from animal reservoirs (including highly pathogenic H7N9 and H5N1 viruses). An understanding of past influenza virus pandemics and the lessons that we have learnt from them has therefore never been more pertinent.

The human viral challenge model: accelerating the evaluation of respiratory antivirals, vaccines and novel diagnostics

The Human Viral Challenge (HVC) model has, for many decades, helped in the understanding of respiratory viruses and their role in disease pathogenesis. In a controlled setting using small numbers of volunteers removed from community exposure to other infections, this experimental model enables proof of concept work to be undertaken on novel therapeutics, including vaccines, immunomodulators and antivirals, as well as new diagnostics.Crucially, unlike conventional phase 1 studies, challenge studies include evaluable efficacy endpoints that then guide decisions on how to optimise subsequent field studies, as recommended by the FDA and thus licensing studies that follow. Such a strategy optimises the benefit of the studies and identifies possible threats early on, minimising the risk to subsequent volunteers but also maximising the benefit of scarce resources available to the research group investing in the research. Inspired by the principles of the 3Rs (Replacement, Reduction and Refinement) now commonly applied in the preclinical phase, HVC studies allow refinement and reduction of the subsequent development phase, accelerating progress towards further statistically powered phase 2b studies. The breadth of data generated from challenge studies allows for exploration of a wide range of variables and endpoints that can then be taken through to pivotal phase 3 studies.We describe the disease burden for acute respiratory viral infections for which current conventional development strategies have failed to produce therapeutics that meet clinical need. The Authors describe the HVC model's utility in increasing scientific understanding and in progressing promising therapeutics through development.The contribution of the model to the elucidation of the virus-host interaction, both regarding viral pathogenicity and the body's immunological response is discussed, along with its utility to assist in the development of novel diagnostics.Future applications of the model are also explored.

Insights from unusual aspects of the 1918 influenza pandemic

The 1918 influenza pandemic was the most lethal single event in modern history. Besides its mortality the 1918 pandemic was unusual for several reasons. It preferentially killed young adults from 20 to 40 y with a peak mortality at age 28 y. Mortality was highly variable with death rates varying by at least 10 fold within similar groups of citizens, soldiers, cities and islands. Secondary bacterial pneumonia following influenza was the overwhelming cause of death and not viral pneumonitis or acute lung injury. Clinical expressions of the 1918 pandemic were unusual with bleeding into the respiratory tree including epistaxis and dark blue cyanotic skin. The 1918 influenza virus apparently ceased circulation in the human population in the early 1920s but continued to evolve in pigs. Immunizations using viruses from 1918 and 2009 can cross-protect laboratory animals even though the human mortality outcomes were very different between the first pandemics of the 20th and 21st centuries. Unusual aspects of historical epidemics may help to reconstruct what actually occurred in 1918 and thus better prepare for the next pandemic.

Influenza activity in Saint Joseph, Missouri 1910-1923: Evidence for an early wave of the 1918 pandemic

While the 1918/1919 H1N1 influenza pandemic is widely recognized as a "worst-case scenario" for the emergence of a new influenza strain, relatively little is known about the origin of the responsible virus and its pattern of spread. Most studies of this virus in the United States rely on temporally and spatially aggregated data. Location-specific studies of the impact of the 1918 pandemic strain in the United States have been confined primarily to large cities on the East Coast or West Coast. In this study, data on pneumonia and influenza fatalities from 1910-1923 have been extracted from death certificates for Saint Joseph, Missouri, a typical mid-sized city in the central United States. An increase in pneumonia and influenza mortality was noted starting in the 1915/1916 influenza season. Initially, increased mortality was observed in infants and the elderly. In February 1918, an age-shift typical of pandemic strains of virus was seen, as the burden of mortality shifted to young adults, a characteristic of the 1918 pandemic virus. These results provide one of the first confirmations of the existence of a "herald wave" of influenza activity in the United States prior to the recognized start of the H1N1 pandemic in Spring 1918. This study is one of very few that measures the impact of 1918/1919 influenza in a particular location in the central United States.

Influenza infectious dose may explain the high mortality of the second and third wave of 1918-1919 influenza pandemic

Background

It is widely accepted that the shift in case-fatality rate between waves during the 1918 influenza pandemic was due to a genetic change in the virus. In animal models, the infectious dose of influenza A virus was associated to the severity of disease which lead us to propose a new hypothesis. We propose that the increase in the case-fatality rate can be explained by the dynamics of disease and by a dose-dependent response mediated by the number of simultaneous contacts a susceptible person has with infectious ones.

Methods

We used a compartment model with seasonality, waning of immunity and a Holling type II function, to model simultaneous contacts between a susceptible person and infectious ones. In the model, infected persons having mild or severe illness depend both on the proportion of infectious persons in the population and on the level of simultaneous contacts between a susceptible and infectious persons. We further allowed for a high or low rate of waning immunity and volunteer isolation at different times of the epidemic.

Results

In all scenarios, case-fatality rate was low during the first wave (Spring) due to a decrease in the effective reproduction number. The case-fatality rate in the second wave (Autumn) depended on the ratio between the number of severe cases to the number of mild cases since, for each 1000 mild infections only 4 deaths occurred whereas for 1000 severe infections there were 20 deaths. A third wave (late Winter) was dependent on the rate for waning immunity or on the introduction of new susceptible persons in the community. If a group of persons became voluntarily isolated and returned to the community some days latter, new waves occurred. For a fixed number of infected persons the overall case-fatality rate decreased as the number of waves increased. This is explained by the lower proportion of infectious individuals in each wave that prevented an increase in the number of severe infections and thus of the case-fatality rate.

Conclusion

The increase on the proportion of infectious persons as a proxy for the increase of the infectious dose a susceptible person is exposed, as the epidemic develops, can explain the shift in case-fatality rate between waves during the 1918 influenza pandemic.

Origins of the Spanish Influenza pandemic (1918-1920) and its relation to the First World War

The virus which was responsible for the first benign wave of the Spanish Influenza in the spring of 1918, and which was to become extremely virulent by the end of the summer of 1918, was inextricably associated with the soldiers who fought during the First World War. The millions of young men who occupied the military camps and trenches were the substrate on which the influenza virus developed and expanded. Many factors contributed to it, such as: the mixing on French soil of soldiers and workers from the five continents, the very poor quality of life of the soldiers, agglomeration, stress, fear, war gasses used for the first time in history in a massive and indiscriminate manner, life exposed to the elements, cold weather, humidity and contact with birds, pigs and other animals, both wild and domestic. Today, this combination of circumstances is not present and so it seems unlikely that new pandemics, such as those associated with the avian influenza or swine influenza, will emerge with the virulence which characterized the Spanish Influenza during the autumn of 1918.

Mortality burden of the 1918-1919 influenza pandemic in Europe

Background  The origin and estimated death toll of the 1918–1919 epidemic are still debated. Europe, one of the candidate sites for pandemic emergence, has detailed pandemic mortality information.

Objective  To determine the mortality impact of the 1918 pandemic in 14 European countries, accounting for approximately three‐quarters of the European population (250 million in 1918).

Methods  We analyzed monthly all‐cause civilian mortality rates in the 14 countries, accounting for approximately three‐quarters of the European population (250 million in 1918). A periodic regression model was applied to estimate excess mortality from 1906 to 1922. Using the 1906–1917 data as a training set, the method provided a non‐epidemic baseline for 1918–1922. Excess mortality was the mortality observed above this baseline. It represents the upper bound of the mortality attributable to the flu pandemic.

Results  Our analysis suggests that 2·64 million excess deaths occurred in Europe during the period when Spanish flu was circulating. The method provided space variation of the excess mortality: the highest and lowest cumulative excess/predicted mortality ratios were observed in Italy (+172%) and Finland (+33%). Excess‐death curves showed high synchrony in 1918–1919 with peak mortality occurring in all countries during a 2‐month window (Oct–Nov 1918).

Conclusions  During the Spanish flu, the excess mortality was 1·1% of the European population. Our study highlights the synchrony of the mortality waves in the different countries, which pleads against a European origin of the pandemic, as was sometimes hypothesized.

Impact of two interventions on timeliness and data quality of an electronic disease surveillance system in a resource limited setting (Peru): a prospective evaluation

Background

A timely detection of outbreaks through surveillance is needed in order to prevent future pandemics. However, current surveillance systems may not be prepared to accomplish this goal, especially in resource limited settings. As data quality and timeliness are attributes that improve outbreak detection capacity, we assessed the effect of two interventions on such attributes in Alerta, an electronic disease surveillance system in the Peruvian Navy.

Methods

40 Alerta reporting units (18 clinics and 22 ships) were included in a 12-week prospective evaluation project. After a short refresher course on the notification process, units were randomly assigned to either a phone, visit or control group. Phone group sites were called three hours before the biweekly reporting deadline if they had not sent their report. Visit group sites received supervision visits on weeks 4 & 8, but no phone calls. The control group sites were not contacted by phone or visited. Timeliness and data quality were assessed by calculating the percentage of reports sent on time and percentage of errors per total number of reports, respectively.

Results

Timeliness improved in the phone group from 64.6% to 84% in clinics (+19.4 [95% CI, +10.3 to +28.6]; p < 0.001) and from 46.9% to 77.3% on ships (+30.4 [95% CI, +16.9 to +43.8]; p < 0.001). Visit and control groups did not show significant changes in timeliness. Error rates decreased in the visit group from 7.1% to 2% in clinics (-5.1 [95% CI, -8.7 to -1.4]; p = 0.007), but only from 7.3% to 6.7% on ships (-0.6 [95% CI, -2.4 to +1.1]; p = 0.445). Phone and control groups did not show significant improvement in data quality.

Conclusion

Regular phone reminders significantly improved timeliness of reports in clinics and ships, whereas supervision visits led to improved data quality only among clinics. Further investigations are needed to establish the cost-effectiveness and optimal use of each of these strategies.

The animal-human interface and infectious disease in industrial food animal production: rethinking biosecurity and biocontainment

Understanding interactions between animals and humans is critical in preventing outbreaks of zoonotic disease. This is particularly important for avian influenza. Food animal production has been transformed since the 1918 influenza pandemic. Poultry and swine production have changed from small-scale methods to industrial-scale operations. There is substantial evidence of pathogen movement between and among these industrial facilities, release to the external environment, and exposure to farm workers, which challenges the assumption that modern poultry production is more biosecure and biocontained as compared with backyard or small holder operations in preventing introduction and release of pathogens. An analysis of data from the Thai government investigation in 2004 indicates that the odds of H5N1 outbreaks and infections were significantly higher in large-scale commercial poultry operations as compared with backyard flocks. These data suggest that successful strategies to prevent or mitigate the emergence of pandemic avian influenza must consider risk factors specific to modern industrialized food animal production.

The Spanish flu in Denmark

The spread of H5N1 influenza and the similarity between this avian virus and the Spanish flu virus causes fear of a new influenza pandemic, but data from the Spanish flu may also be of guidance in planning for preventive measures. Using data on influenza cases, influenza deaths and total deaths for Denmark and for Danish towns from 1917 to 1921, and population data from the 1916 and 1921 censuses, we analysed incident cases, cumulative, age-specific and age-standardized rates. Overall, more than 900,000 persons contracted flu during the y 1918-1920, and 1 out of 50 patients died from the disease. An early wave of the flu occurred in the capital and major towns, but not in peripheral towns. Influenza incidence in 1918 peaked at age 5-15 y, closely followed by the age groups 1-5 y and 15-65 y, but the influenza mortality was highest in the age groups 0-1 y and 15-65 y, with a peak mortality at age 20-34 y producing a W curve for mortality by age. The background for the better outcome in children aged 1-15 y as well as for the disease immunity in the elderly population should be further investigated.

A cohort study of tuberculosis and influenza mortality in the twentieth century

We reviewed period and cohort mortality for tuberculosis and influenza and pneumonia over the twentieth century and data on the roles of influenza and tuberculosis as underlying and contributory causes of death. As would be consistent with long-term trends, each cohort had lower tuberculosis mortality but there was no decisive downturn in age specific tuberculosis mortality for any male cohort until after 1945. Tuberculosis mortality among females fell steadily from cohort to cohort as well as within each cohort. In every cohort born from around 1890 to around 1930, tuberculosis mortality was higher among women than among men at ages under 30, suggesting that prevalence in women was also higher, but death rates of females crossed under those of males at about age 30. Tuberculosis death rates rose more for males than females around 1918; however, any unusual increase that could be attributable to the 1918 influenza pandemic must have been brief. Contrary to expectations in the medical community, tuberculosis mortality did not rise following the 1918 influenza pandemic. Some portion of the rise in death rates around 1918 may have been associated with the influenza, but a comparison of the increase in male tuberculosis mortality during and after World War II, when there was no influenza pandemic, with male mortality in a similar period during and after World War I suggests that any excess in tuberculosis mortality among males in both periods may have been due to wartime mobilization rather than influenza.

Influenza vaccines have a short but illustrious history

Isolation of the causative virus of influenza in 1933, followed by the discovery of embryonated hen eggs as a substrate, quickly led to the formulation of vaccines. Virus-containing allantoic fluid was inactivated with formalin. The phenomenon of antigenic drift of the virus HA was soon recognized and, as WHO began to coordinate the world influenza surveillance, it became easier for manufacturers to select an up-to-date virus. Influenza vaccines remain unique in that the virus strain composition is reviewed yearly but modern attempts are being made to free manufacturers from this yolk by investigating internal virus proteins including M2e and NP as “universal” vaccines covering all virus sub types. Recent technical innovations have been the use of Vero and MDCK cells as the virus cell substrate, the testing of two new adjuvants and the exploration of new presentations to the nose or epidermal layers as DNA or antigen mixtures. The international investment into public health measures for a global human outbreak of avian H5N1 influenza is leading to enhanced production of conventional vaccine and to a new research searchlight on T cell epitope vaccines, viral live attenuated carriers of influenza proteins and even more innovative substrates to cultivate virus, including plant cells.

The prospect of pandemic influenza: why should the optometrist be concerned about a public health problem?

BACKGROUND

Optometrists are uniquely placed in the health care field because they provide both services as well as goods to patients. In the event of an influenza pandemic, optometrists may be challenged with a host of issues, including impediments to clinical patient care, manufacture and delivery of ophthalmic devices, and maintaining business continuity and infection control.

OVERVIEW

This report reviews pandemic influenza, the effect of a pandemic event on business survival, and response measures for the primary eye care provider. The ethical and legal issues surrounding control of a pandemic influenza and the prospect of telemedicine as a form of social distancing are also discussed.

CONCLUSIONS

Knowledge of the pharmacologic and nonpharmacologic measures to control a pandemic influenza will help prepare the eye care provider for addressing challenges to patient care and business continuity in the face of a highly contagious disease. Understanding the legal and ethical issues that arise during a pandemic event will help optometrists make informed choices as health care professionals and as citizens.

Spanish influenza in Japanese armed forces, 1918-1920

Medical records of Japanese army hospitals show high death rates during the first influenza pandemic.

With the recent outbreaks of avian influenza A (H5N1), the risk for the next influenza pandemic has increased. For effective countermeasures against the next pandemic, investigation of past pandemics is necessary. We selected cases diagnosed as influenza from medical records and hospitalization registries of Japanese army hospitals during 1918–1920, the Spanish influenza era, and investigated clinical features and circumstances of outbreaks. Admission lists showed a sudden increase in the number of inpatients with influenza in November 1918 and showed the effect of the first wave of this pandemic in Tokyo. The death rate was high (6%–8%) even though patients were otherwise healthy male adults.

The evolutionary emergence of pandemic influenza

Pandemic influenza remains a serious public health threat and the processes involved in the evolutionary emergence of pandemic influenza strains remain incompletely understood. Here, we develop a stochastic model for the evolutionary emergence of pandemic influenza, and use it to address three main questions. (i) What is the minimum annual number of avian influenza virus infections required in humans to explain the historical rate of pandemic emergence? (ii) Are such avian influenza infections in humans more likely to give rise to pandemic strains if they are driven by repeated cross-species introductions, or by low-level transmission of avian influenza viruses between humans? (iii) What are the most effective interventions for reducing the probability that an influenza strain with pandemic potential will evolve? Our results suggest that if evolutionary emergence of past pandemics has occurred primarily through viral reassortment in humans, then thousands of avian influenza virus infections in humans must have occurred each year for the past 250 years. Analyses also show that if there is epidemiologically significant variation among avian influenza virus genotypes, then avian virus outbreaks stemming from repeated cross-species transmission events result in a greater likelihood of a pandemic strain evolving than those caused by low-level transmission between humans. Finally, public health interventions aimed at reducing the duration of avian virus infections in humans give the greatest reduction in the probability that a pandemic strain will evolve.

Amino acid and codon use: in two influenza viruses and three hosts

OBJECTIVE

The aim of this study was to compare the use of amino acids and codons in influenza viruses A and B and in their common hosts, to highlight any relevant difference.

METHODS

The frequency of the 20 amino acids and of the 61 codons was studied in influenza viruses A, B, and in man, pig, and chicken. The correlation in amino acid and codon use among these hosts was calculated.

RESULTS

The correlation between the frequency of the 20 amino acids and the molecular weight was also calculated and it was very similar in all studied hosts, ranging from 0.506 to 0.595. The correlation of codon frequency among these organisms was highest between man and chicken (r=0.974), and lowest between pig and virus B (r=0.147).

CONCLUSIONS

The important correlation in codon use among the three hosts and the two viruses suggests there was a remote lateral gene transfer among the three hosts and the two viruses. The higher use of alanine, leucine, and proline in man versus virus A is significant.

Model answers or trivial pursuits? The role of mathematical models in influenza pandemic preparedness planning

The panzootic of H5N1 influenza in birds has raised concerns that the virus will mutate to spread more readily in people, leading to a human pandemic. Mathematical models have been used to interpret past pandemics and outbreaks, and to thus model possible future pandemic scenarios and interventions. We review historical influenza outbreak and transmission data, and discuss the way in which modellers have used such sources to inform model structure and assumptions. We suggest that urban attack rates in the 1918-1919 pandemic were constrained by prior immunity, that R(0) for influenza is higher than often assumed, and that control of any future pandemic could be difficult in the absence of significant prior immunity. In future, modelling assumptions, parameter estimates and conclusions should be tested against as many relevant data sets as possible. To this end, we encourage researchers to access FluWeb, an on-line influenza database of historical pandemics and outbreaks.

Vaccination with cell immunoglobulin mucin-1 antibodies and inactivated influenza enhances vaccine-specific lymphocyte proliferation, interferon-gamma production and cross-strain reactivity

Influenza virus causes a contagious and potentially serious infection of the upper respiratory tract. While neutralizing antibodies are protective against infection, the problem of antigenic drift remains, requiring the constant monitoring and development of new vaccines. The magnitude of this situation is underscored by the emergence of new potentially human pathogenic influenza strains, avian H5N1 being the most recent example. We present evidence that antibodies against T cell immunoglobulin mucin-1 (TIM-1), a recently identified immunomodulatory molecule, stimulate cellular immunity against influenza viruses and cross-strain immune reactivity. To determine potential immunostimulatory properties of anti-TIM-1, mice were vaccinated with inactivated influenza virus in the presence or absence of TIM-1-specific monoclonal antibodies. Development of cellular immunity against both the influenza strain used for immunization and serotypically distinct virus strains was monitored 3 weeks after vaccination by determining antigen-specific lymphocyte proliferation and cytokine production. Results show that TIM-1 antibodies enhance antigen-specific cellular proliferation (P < 0.05) and interferon (IFN)-gamma production (P < 0.01). Using blocking anti-CD4 and CD8 antibodies, it was observed that antigen-specific cellular proliferation is CD4-dependent and that the majority of proliferating cells are CD4+. Finally, vaccination with inactivated influenza virus with TIM-1 antibody results in the significant (P < 0.001) induction of proliferation and IFN-gamma production upon stimulation with one of three serologically distinct strains. TIM-1 antibodies demonstrate an adjuvant effect promoting antigen-specific cellular proliferation and IFN-gamma production, which are important for the promotion of cell-mediated immunity. These results are the first to suggest that TIM-1 antibody may serve as a potent adjuvant in the development of new influenza virus vaccines.

Vaccination with cell immunoglobulin mucin-1 antibodies and inactivated influenza enhances vaccine-specific lymphocyte proliferation, interferon-γ production and cross-strain reactivity

Influenza virus causes a contagious and potentially serious infection of the upper respiratory tract. While neutralizing antibodies are protective against infection, the problem of antigenic drift remains, requiring the constant monitoring and development of new vaccines. The magnitude of this situation is underscored by the emergence of new potentially human pathogenic influenza strains, avian H5N1 being the most recent example. We present evidence that antibodies against T cell immunoglobulin mucin-1 (TIM-1), a recently identified immunomodulatory molecule, stimulate cellular immunity against influenza viruses and cross-strain immune reactivity. To determine potential immunostimulatory properties of anti-TIM-1, mice were vaccinated with inactivated influenza virus in the presence or absence of TIM-1-specific monoclonal antibodies. Development of cellular immunity against both the influenza strain used for immunization and serotypically distinct virus strains was monitored 3 weeks after vaccination by determining antigen-specific lymphocyte proliferation and cytokine production. Results show that TIM-1 antibodies enhance antigen-specific cellular proliferation (P &lt; 0·05) and interferon (IFN)-γ production (P &lt; 0·01). Using blocking anti-CD4 and CD8 antibodies, it was observed that antigen-specific cellular proliferation is CD4-dependent and that the majority of proliferating cells are CD4+. Finally, vaccination with inactivated influenza virus with TIM-1 antibody results in the significant (P &lt; 0·001) induction of proliferation and IFN-γ production upon stimulation with one of three serologically distinct strains. TIM-1 antibodies demonstrate an adjuvant effect promoting antigen-specific cellular proliferation and IFN-γ production, which are important for the promotion of cell-mediated immunity. These results are the first to suggest that TIM-1 antibody may serve as a potent adjuvant in the development of new influenza virus vaccines.

Glycan microarray analysis of the hemagglutinins from modern and pandemic influenza viruses reveals different receptor specificities

Influenza A virus specificity for the host is mediated by the viral surface glycoprotein hemagglutinin (HA), which binds to receptors containing glycans with terminal sialic acids. Avian viruses preferentially bind to alpha2-3-linked sialic acids on receptors of intestinal epithelial cells, whereas human viruses are specific for the alpha2-6 linkage on epithelial cells of the lungs and upper respiratory tract. To define the receptor preferences of a number of human and avian H1 and H3 viruses, including the 1918 H1N1 pandemic strains, their hemagglutinins were analyzed using a recently described glycan array. The array, which contains 200 carbohydrates and glycoproteins, not only revealed clear differentiation of receptor preferences for alpha2-3 and/or alpha2-6 sialic acid linkage, but could also detect fine differences in HA specificity, such as preferences for fucosylation, sulfation and sialylation at positions 2 (Gal) and 3 (GlcNAc, GalNAc) of the terminal trisaccharide. For the two 1918 HA variants, the South Carolina (SC) HA (with Asp190, Asp225) bound exclusively alpha2-6 receptors, while the New York (NY) variant, which differed only by one residue (Gly225), had mixed alpha2-6/alpha2-3 specificity, especially for sulfated oligosaccharides. Only one mutation of the NY variant (Asp190Glu) was sufficient to revert the HA receptor preference to that of classical avian strains. Thus, the species barrier, as defined by the receptor specificity preferences of 1918 human viruses compared to likely avian virus progenitors, can be circumvented by changes at only two positions in the HA receptor binding site. The glycan array thus provides highly detailed profiles of influenza receptor specificity that can be used to map the evolution of new human pathogenic strains, such as the H5N1 avian influenza.

A socially neutral disease? Individual social class, household wealth and mortality from Spanish influenza in two socially contrasting parishes in Kristiania 1918-19

The Spanish influenza pandemic of 1918-19 was one of the most devastating diseases in history, killing perhaps as many as 50-100 million people worldwide. Much of the literature since 1918 has favored the view that mortality from Spanish influenza was class neutral. This view has prevailed, even though several contemporary surveys showed that there indeed were clear differences between the classes in disease incidence and that case fatality rates from influenza and pneumonia also varied according to socioeconomic status. Furthermore, studies of more recent influenza epidemics have also shown that there can be clear class differentials in mortality in this type of illness--is there any reason to believe that Spanish influenza was different? This paper is the first study in which individual- and household-level data which are unique for the period are utilized to test the conservative hypothesis that Spanish influenza was a socially neutral disease with respect to mortality. Through the use of Cox regressions in an analysis of two socially contrasting parishes in the Norwegian capital city of Kristiania, it is shown that apartment size as an indicator of wealth of a household, in addition to social status of place of residence, were the only socioeconomic variables that had an independent and significant effect on mortality after controlling for age, sex and marital status.

Epidemiological evidence of an early wave of the 1918 influenza pandemic in New York City

The 1918 "Spanish flu" was the fastest spreading and most deadly influenza pandemic in recorded history. Hypotheses of its origin have been based on a limited collection of case and outbreak reports from before its recognized European emergence in the summer of 1918. These anecdotal accounts, however, remain insufficient for determining the early diffusion and impact of the pandemic virus. Using routinely collected monthly age-stratified mortality data, we show that an unmistakable shift in the age distribution of epidemic deaths occurred during the 1917/1918 influenza season in New York City. The timing, magnitude, and age distribution of this mortality shift provide strong evidence that an early wave of the pandemic virus was present in New York City during February-April 1918.

The impact of influenza on the health and health care utilisation of elderly people

Despite intensive research, influenza viruses still present one of the major causes of respiratory disease throughout the world. The elderly population and those individuals considered "at risk" due to presenting co-morbidity are especially vulnerable to influenza infection; this is evident from increased rates of morbidity and mortality in these populations during winter epidemic periods. Successful vaccination campaigns have targeted these groups over the last few years, providing protection to an increasing number of susceptible individuals. However, during periods of influenza virus activity there are still seasonal pressures put on both primary and secondary health care services. In the event of a serious influenza epidemic or pandemic, these burdens could jeopardise health care provision to at risk populations. In this report we discuss current issues surrounding the impact of influenza on the health care utilisation of elderly people.