The burden of influenza in the United States can vary from year to year depending on which viruses are circulating, how many people receive an influenza vaccination, and how effective the vaccination is in that particular year. During the 2019-2020 flu season, around 25,000 people lost their lives to the disease. Although most people recover from influenza without needing medical care, the disease can be deadly among young children, the elderly, and those with weakened immune systems or chronic illnesses.

Deaths due to influenza Even though most people recover from influenza without medical care, influenza and pneumonia can be deadly, especially for older people and those with certain preexisting conditions. Influenza is a common cause of pneumonia and although most cases of influenza do not develop into pneumonia, those that do are often more severe and more deadly. Deaths due to influenza are most common among the elderly, with a mortality rate of around 7.4 per 100,000 population during the 2021-2022 flu season. In comparison, the mortality rate for those aged 50 to 64 years was just 1.2 per 100,000 population.

Flu vaccinations The most effective way to prevent influenza is to receive a yearly influenza vaccination. These vaccines have proven to be safe and are usually cheap and easily accessible. Nevertheless, every year a large share of the population in the United States still fails to get vaccinated against influenza. For example, in the 2021-2022 flu season only 37 percent of those aged 18 to 49 years received a flu vaccination. Unsurprisingly, children and the elderly are the most likely to get vaccinated. It is estimated that during the 2021-2022 flu season vaccinations prevented over 618 thousand influenza cases among children aged 6 months to 4 years.

Influenza and pneumonia caused around 12.3 deaths in the U.S. per 100,000 population in 2019. Influenza and pneumonia are among the leading causes of death in the United States, accounting for around 1.6 percent of all deaths in 2020. Influenza, or the flu, is a viral infection that is highly contagious and especially common in the winter season. Influenza is a common cause of pneumonia, although most cases of the flu do not develop into pneumonia. Pneumonia is an infection or inflammation of the lungs and is particularly deadly among young children and the elderly.

Influenza cases

Influenza is very common in the United States, with an estimated 35 million cases reported in 2019-2020. Common symptoms of the flu include cough, fever, runny or stuffy nose, sore throat and headache. Symptoms can be mild but can also be severe enough to require medical attention. In 2019-2020, there were around 16 million influenza-related medical visits in the United States.

Prevention

To prevent contracting the flu people can take everyday precautions such as regularly washing their hands and avoiding those who are sick, but the best way to prevent the flu is by receiving the flu vaccination every year. Receiving a flu vaccination is especially important for young children and the elderly as they are most susceptible to flu complications and associated death. In 2021, around 75 percent of those aged 65 years and older received a flu vaccine, while only 38 percent of those aged 18 to 49 years had done so.

During the 2022-2023 flu season in the United States, around 21,401 people died from influenza. The vast majority of deaths due to influenza occur among the elderly, with those aged 65 years and older accounting for 15,399 deaths during the 2022-2023 flu season. During this time, the mortality rate from influenza among those aged 65 years and older was around 26.6 per 100,000 population, compared to a mortality rate of .7 per 100,000 population among those aged 18 to 49 years. Influenza deaths Although most people recover from influenza without the need of medical care, influenza and pneumonia are still major causes of death in the United States. Influenza is a common cause of pneumonia and cases in which influenza develops into pneumonia tend to be more severe and more deadly. However, the impact of influenza varies from year to year depending on which viruses are circulating. For example, during the 2017-2018 flu season around 51,000 people died due to influenza, whereas in 2022-2023 total deaths amounted to 21,000. Preventing death The most effective way to prevent influenza is to receive a yearly influenza vaccination. These vaccines have proven to be safe and are usually cheap and easily accessible. Each year, flu vaccinations prevent thousands of influenza cases, hospitalizations and deaths. It was estimated that during the 2022-2023 flu season, vaccinations prevented the deaths of around 2,479 people aged 65 years and older.

Following the outbreak of the H1N1 influenza pandemic of 1918, which came to be known as the Spanish Flu, the number of deaths due to influenza and pneumonia soared. Pneumonia was caused either by the influenza or by a bacterial superinfection that took hold due to the patient's weakened state as a result of the influenza, for this reason, influenza deaths and pneumonia deaths were recorded together as one. Pennsylvania had the highest mortality rate due to the pandemic, where there were over 880 fatalities per 100,000 people; meaning that approximately 0.9 percent of the state's population died from the Spanish Flu pandemic in 1918.

When compared with the 1915 mortality rates, many states, such as California and Pennsylvania, saw their mortality rate due to influenza and pneumonia increase five-fold by 1818, which was the worst year of the pandemic. While the mortality rate decreased significantly in the year 1919, there was no US state where it fell to it's pre-pandemic level, and the 1919 mortality rate was still double the pre-pandemic rate in some states such as California, South Carolina and Washington.

Influenza, also called the flu, is one of the most infectious diseases worldwide. Its symptoms range from mild to severe, and include sore throat, cough, runny nose, fever, headache, and muscle pain, but can also cause severe illness and death among high-risk populations such as the elderly and children. During the 2022-2023 flu season, there were 31 million cases of influenza in the United States.

Influenza deaths Although influenza does not require medical attention for most people, it can be deadly, and causes thousands of deaths every year. The impact of influenza varies from year to year. The number of influenza deaths during the 2021-2022 flu season was 4,977. The vast majority of deaths attributed to influenza during the 2021-2022 flu season occurred among those aged 65 years and older.

Vaccination An annual influenza vaccination remains the most effective way of preventing influenza. During the 2021-2022 flu season, influenza vaccinations prevented an estimated 867 deaths among U.S. adults aged 65 years and older. Although, flu vaccinations are accessible and cheap, a large share of the United States population still fails to get vaccinated every year. In 2021-2022, only 37 percent of those aged 18 to 49 years received a flu vaccination, much lower compared to children and the elderly.

Contact: PD Dr. Kaspar Staub kaspar.staub@iem.uzh.ch

For the LEAD Hub we digitized and analyzed the following historical demographic and epidemiological data for the city and the canton of Zurich the first time: Since the end of the 19th century, the Federal Health Office (Eidgenössisches Gesundheitsamt) published a weekly bulletin on vital statistics, newly reported cases of notifiable infectious diseases, and hospitalisations. For the period January 1910 to December 1970, we have digitized and transcribed the following weekly series:

1. Weekly deaths for residents and non-residents of the city of Zurich. The quality of these historical vital statistics is assessed to be very good in the literature, incompleteness and migration are no longer a problem as compared to earlier years. However, age-, sex- and cause-specific death numbers were not available on the weekly level.
2. Weekly newly reported cases of influenza-like-illness for the canton and the city of Zurich. This series begins with the introduction of the reporting obligation for influenza in the canton of Zürich in mid-July 1918. As these figures do not include mild cases not treated by a doctor and misdiagnoses, they are probably underestimates, but can still track pandemic and seasonal waves. The reporting system and obligation did not change in the observed time period.
3. Weekly new hospitalisation due to influenza in the canton of Zurich. This series ends in 1938.

The original data format in the weekly bulletins are printed, aggregated tables that have been converted into PDFs using a professional book scanner. Transcription of the data was performed by student assistants using a software and running extended quality-controls. The original tables were in German and French, the digitised data set was annotated in English.

The digitized data are organized as a spreadsheet and stored in csv format. The data are organized as rows (representing reporting weeks) and columns (see variable list below). For a few weeks, information in the original sources was missing (indicated by 1 in the “interpolated” variable). In these cases, the missing values were interpolated by averaging the numbers of the week before and the week afterwards.

Codebook:

Worksheet "Data"

• StartReportingPeriod = Start date of the reporting week (dd.mm.yyyy)
• EndReportingPeriod = End date of reporting week (dd.mm.yyyy)
• Interpolated: 1=value for this week has been interpolated; 0=not interpolated
• CityDeathsTotal = Total absolute number of deaths (all-causes) in the City of Zurich (residents and non-residents)
• CityDeathsResidents = Absolute number of deaths (all-causes) in the City of Zurich for residents
• CityDeathsNonresidents = Absolute number of deaths (all-causes) in the City of Zurich for non-residents
• CantonCases = Absolute number of reported new influenza-like-illness cases by physicians in the Canton of Zurich (including the City)
• CityCases = Absolute number of reported new influenza-like-illness cases by physicians in the City of Zurich
• CantonHospitalisationsFluInfections = Absolute number of new hospitalisations due to influenza-like-illness in the Canton of Zurich (including the City)

Worksheet "Population"

• Yearly population numbers for the City and the Canton of Zurich (source)

Social factors have been shown to create differential burden of influenza across different geographic areas. We explored the relationship between potential aggregate-level social determinants and mortality during the 1918 influenza pandemic in Chicago using a historical dataset of 7,971 influenza and pneumonia deaths. Census tract-level social factors, including rates of illiteracy, homeownership, population, and unemployment, were assessed as predictors of pandemic mortality in Chicago. Poisson models fit with generalized estimating equations (GEEs) were used to estimate the association between social factors and the risk of influenza and pneumonia mortality. The Poisson model showed that influenza and pneumonia mortality increased, on average, by 32.2% for every 10% increase in illiteracy rate adjusted for population density, homeownership, unemployment, and age. We also found a significant association between transmissibility and population density, illiteracy, and unemployment but not homeownership. Lastly, analysis of the point locations of reported influenza and pneumonia deaths revealed fine-scale spatiotemporal clustering. This study shows that living in census tracts with higher illiteracy rates increased the risk of influenza and pneumonia mortality during the 1918 influenza pandemic in Chicago. Our observation that disparities in structural determinants of neighborhood-level health lead to disparities in influenza incidence in this pandemic suggests that disparities and their determinants should remain targets of research and control in future pandemics.

Results data for the thesis on estimating the age-, sex-, cause-specific excess mortality during the COVID-19 pandemic in Hong Kong and South Korea.Thesis abstractBackgroundFew studies used a consistent methodology and adjusted for the risk of influenza-like illness (ILI) in historical mortality trends when estimating and comparing the cause-specific excess mortality (EM) during the COVID-19 pandemic. Previous studies demonstrated that excess mortality was widely reported from CVD and among the elderly. This study aims to estimate and compare the overall, age-, sex-, and cause-specific excess mortality during the COVID-19 pandemic in Hong Kong (HK) and South Korea (SK) with consideration of the impact of ILI.MethodsIn this population-based study, we first fitted a generalized additive model to the monthly mortality data from Jan 2010 to Dec 2019 in HK and SK before the COVID-19 pandemic. Then we applied the fitted model to estimate the EM from Jan 2020 to Dec 2022. The month index was modelled with a natural cubic spline. Akaike information criterion (AIC) was used to select the number of knots for the spline and inclusion of covariates such as monthly mean temperature, absolute humidity, ILI consultation rate, and the proxy for flu activity.FindingsFrom 2020 to 2022, the EM in HK was 239.8 (95% CrI: 184.6 to 293.9) per 100,000 population. Excess mortality from respiratory diseases (RD) (ICD-10 code: J00-J99), including COVID-19 deaths coded as J98.8, was 181.3 (95% CrI: 149.9 to 210.4) per 100,000. Except for RD, the majority of the EM in HK was estimated from cardiovascular diseases (CVD) (22.4% of the overall EM), influenza and pneumonia (16.2%), ischemic heart disease (8.9%), ill-defined causes (8.6%) and senility (6.7%). No statistically significant reduced deaths were estimated among other studied causes.From 2020 to 2022, the EM in SK was 204.7 (95% CrI: 161.6 to 247.2) per 100,000 population. Of note, COVID-19 deaths in SK were not included in deaths from RD but were recorded with the codes for emergency use as U07.1 or U07.2. The majority of the EM was estimated from ill-defined causes (32.0% of the overall EM), senility (16.6%), cerebrovascular disease (6.8%) and cardiovascular diseases (6.1%). Statistically significant reduction in mortality with 95 CrI lower than zero was estimated from vascular, other and unspecified dementia (-26.9% of expected deaths), influenza and pneumonia (-20.7%), mental and behavioural disorders (-18.8%) and respiratory diseases (-7.7%).InterpretationExcluding RD in HK which includes COVID-19 deaths, the majority of the EM in HK and SK was from CVD and senility. Mortality from influenza and pneumonia was estimated to have a statistically significant increase in HK but a decrease in SK probability due to different coding practices. HK had a heavier burden of excess mortality in the elderly age group 70-79 years and 80 years or above, while SK had a heavier burden in the age group of 60-69 years. Both HK and SK have a heavier burden of excess mortality from males than females. Better triage systems for identifying high-risk people of the direct or indirect impact of the epidemic are needed to minimize preventable mortality.

The influenza pandemic of 1918, known as the Spanish Flu, was one of the deadliest and widespread pandemics in human history. The scale of the outbreak, as well as limitations in technology, medicine and communication, create difficulties when trying to uncover accurate figures relating to the pandemic. Estimates suggest that the virus, known as the H1N1 influenza virus, infected more than one quarter of the global population, which equated to approximately 500 million people in 1920. It was responsible for roughly 25 million fatalities, although some projections suggest that it could have caused double this number of deaths. The exact origins of this strain of influenza remain unclear to this day, however it was first noticed in Western Europe in the latter stages of the First World War. Wartime censorship in Europe meant that the severity of the pandemic was under-reported, while news outlets in neutral Spain were free to report openly about the impact of the virus; this gave the illusion that the virus was particularly strong in Spain, giving way to the term "Spanish Flu".

Effects of the virus

By late summer 1918, the pandemic had spread across the entire continent, and the H1N1 virus had mutated into a deadlier strain that weakened the infected's immune system more than traditional influenzas. Some studies suggest that, in contrast to these traditional influenza viruses, having a stronger immune system was actually a liability in the case of the H1N1 virus as it triggered what is known as a "cytokine storm". This is where white blood cells release proteins called cytokines, which signal the body to attack the virus, in turn releasing more white blood cells which release more cytokines. This cycle over-works and greatly weakens the immune system, often giving way to other infections; most commonly pneumonia in the case of the Spanish Flu. For this reason, the Spanish Flu had an uncommonly high fatality rate among young adults, who are traditionally the healthiest group in society. Some theories for the disproportionate death-rate among young adults suggest that the elderly's immune systems benefitted from exposure to earlier influenza pandemics, such as the "Asiatic/Russian Flu" pandemic of 1889.

Decrease in life expectancy As the war in Europe came to an end, soldiers returning home brought the disease to all corners of the world, and the pandemic reached global proportions. Isolated and under-developed nations were especially vulnerable; particularly in Samoa, where almost one quarter of the population died within two months and life expectancy fell to just barely over one year for those born in 1918; this was due to the arrival of a passenger ship from New Zealand in November 1918, where the infected passengers were not quarantined on board, allowing the disease to spread rapidly. Other areas where life expectancy dropped below ten years for those born in 1918 were present-day Afghanistan, the Congo, Fiji, Guatemala, Kenya, Micronesia, Serbia, Tonga and Uganda. The British Raj, now Bangladesh, India and Pakistan, saw more fatalities than any other region, with as many as five percent of the entire population perishing as a result of the pandemic. The pandemic also had a high fatality rate among pregnant women and infants, and greatly impacted infant mortality rates across the world. There were several waves of the pandemic until late 1920, although they decreased in severity as time progressed, and none were as fatal as the outbreak in 1918. A new strain of the H1N1 influenza virus did re-emerge in 2009, and was colloquially known as "Swine Flu"; thankfully it had a much lower fatality rate due to medical advancements across the twentieth century.

Source and number of deaths (from all causes) recorded by selected locations during the 1918 flu pandemic.

Social factors have been shown to create differential burden of influenza across different geographic areas. We explored the relationship between potential aggregate-level social determinants and mortality during the 1918 influenza pandemic in Chicago using a historical dataset of 7,971 influenza and pneumonia deaths. Census tract-level social factors, including rates of illiteracy, homeownership, population, and unemployment, were assessed as predictors of pandemic mortality in Chicago. Poisson models fit with generalized estimating equations (GEEs) were used to estimate the association between social factors and the risk of influenza and pneumonia mortality. The Poisson model showed that influenza and pneumonia mortality increased, on average, by 32.2% for every 10% increase in illiteracy rate adjusted for population density, homeownership, unemployment, and age. We also found a significant association between transmissibility and population density, illiteracy, and unemployment but not homeownership. Lastly, analysis of the point locations of reported influenza and pneumonia deaths revealed fine-scale spatiotemporal clustering. This study shows that living in census tracts with higher illiteracy rates increased the risk of influenza and pneumonia mortality during the 1918 influenza pandemic in Chicago. Our observation that disparities in structural determinants of neighborhood-level health lead to disparities in influenza incidence in this pandemic suggests that disparities and their determinants should remain targets of research and control in future pandemics.

As of January 6, 2022, an average of 1,192 people per day have died from COVID-19 in the U.S. since the first case was confirmed in the country on January 20th the year before. On an average day, nearly 8,000 people die from all causes in the United States, based on data from 2019. Based on the latest information, roughly one in seven deaths each day were related to COVID-19 between January 2020 and January 2022. However, there were even days when more than every second death in the U.S. was connected to COVID-19. The daily death toll from the seasonal flu, using preliminary maximum estimates from the 2019-2020 influenza season, stood at an average of around 332 people. We have to keep in mind that a comparison of influenza and COVID-19 is somewhat difficult. COVID-19 cases and deaths are counted continuously since the begin of the pandemic, whereas flue counts are seasonal and often less accurate. Furthermore, during the last two years, COVID-19 more or less 'replaced' the flu, with COVID-19 absorbing potential flu cases. Many countries reported a very weak seasonal flu activity during the COVID-19 pandemic. But it has yet to be seen how the two infectious diseases will develop side by side during the winter season 2021/2022 and in the years to come.

Symptoms and self-isolation COVID-19 and influenza share similar symptoms – a cough, runny nose, and tiredness – and telling the difference between the two can be difficult. If you have minor symptoms, there is no need to seek urgent medical care, but it is recommended that you self-isolate, whereas rules vary from country to country. Additionally, rules depend on someone's vaccination status and infection history. However, if you think you have the disease, a diagnostic test can show if you have an active infection.

Scientists alert to coronavirus mutations The genetic material of the novel coronavirus is RNA, not DNA. Other notable human diseases caused by RNA viruses include SARS, Ebola, and influenza. A continual problem that vaccine developers encounter is that viruses can mutate, and a treatment developed against a certain virus type may not work on a mutated form. The seasonal flu vaccine, for example, is different each year because influenza viruses are frequently mutating, and it is critical that those genetic changes continue to be tracked.

The child mortality rate in the United States, for children under the age of five, was 462.9 deaths per thousand births in 1800. This means that for every thousand babies born in 1800, over 46 percent did not make it to their fifth birthday. Over the course of the next 220 years, this number has dropped drastically, and the rate has dropped to its lowest point ever in 2020 where it is just seven deaths per thousand births. Although the child mortality rate has decreased greatly over this 220 year period, there were two occasions where it increased; in the 1870s, as a result of the fourth cholera pandemic, smallpox outbreaks, and yellow fever, and in the late 1910s, due to the Spanish Flu pandemic.

description: Disease contingency plan to reduce avian mortality from highly pathogenic avian influenza (HAPI) outbreaks at Rocky Mountain Arsenal National Wildlife Refuge. This plan contains the disease and site history, disease surveillance, field investigations, disease outbreak response action including management options and logistics, and data concerning total number of waterfowl and waterfowl species.; abstract: Disease contingency plan to reduce avian mortality from highly pathogenic avian influenza (HAPI) outbreaks at Rocky Mountain Arsenal National Wildlife Refuge. This plan contains the disease and site history, disease surveillance, field investigations, disease outbreak response action including management options and logistics, and data concerning total number of waterfowl and waterfowl species.

In the United States, influenza vaccination rates differ greatly by age. For example, during the 2022-2023 flu season, around 70 percent of those aged 65 years and older received an influenza vaccination, compared to just 35 percent of those aged 18 to 49 years. The CDC recommends that everyone six months and older in the United States should get vaccinated against influenza every year, with a few exceptions. Although influenza is mild for most people it can lead to hospitalization and even death, especially among the young, the old, and those with certain preexisting conditions.

The impact of flu vaccinations Flu vaccinations are safe and effective, preventing thousands of illnesses, medical visits, and deaths every year. However, the effectiveness of flu vaccines varies each year depending on what flu viruses are circulating that season and the age and health status of the person receiving the vaccination. During the 2022-2023 flu season it was estimated that influenza vaccination prevented almost 31 thousand hospitalizations among those aged 65 years and older. In addition, flu vaccinations prevented 2,479 deaths among those aged 65 years and older as well as 63 deaths among children six months to four years.

The burden of influenza The impact of influenza is different from season to season. However, during the 2022-2023 flu season there were around 31 million cases of influenza in the United States. Furthermore, there were around 21,000 deaths due to influenza, an increase from the previous year but significantly fewer than in 2017-2018 when influenza contributed to 51,000 deaths. Most of these deaths are among the elderly. In 2022-2023 the death rate due to influenza among those aged 65 years and older was around 26.6 per 100,000 population. In comparison, those aged 18 to 49 years had an influenza death rate of just .7 per 100,000 population.

The leading causes of death in the United States have changed significantly from the year 1900 to the present. Leading causes of death in 1900, such as tuberculosis, gastrointestinal infections, and diphtheria have seen huge decreases in death rates and are no longer among the leading causes of death in the United States. However, other diseases such as heart disease and cancer have seen increased death rates. Vaccinations One major factor contributing to the decrease in death rates for many diseases since the year 1900 is the introduction of vaccinations. The decrease seen in the rates of death due to pneumonia and influenza is a prime example of this. In 1900, pneumonia and influenza were the leading causes of death, with around 202 deaths per 100,000 population. However, in 2023 pneumonia and influenza were not even among the ten leading causes of death. Cancer One disease that has seen a large increase in death rates since 1900 is cancer. Cancer currently accounts for almost 20 percent of all deaths in the United States, with death rates among men higher than those for women. The deadliest form of cancer for both men and women is cancer of the lung and bronchus. Some of the most common avoidable risk factors for cancer include smoking, drinking alcohol, sun exposure, and obesity.

In 2023, there were 15.9 deaths from influenza and pneumonia in Canada per 100,000 population. Influenza, more commonly known as the flu, is a highly contagious viral infection and frequent cause of pneumonia. Pneumonia is a more serious infection of the lungs and is particularly deadly among young children, the elderly, and those with certain chronic conditions. Vaccination There exist vaccines for both influenza and pneumonia, and although effectiveness varies, vaccination remains one of the best ways to prevent these illnesses. Nevertheless, only around 34 percent of Canadians received an influenza vaccination in the past year in 2022. The most common reason why Canadian adults received the influenza vaccination was to prevent infection or because they did not want to get sick. Pneumonia hospitalization Every year tens of thousand of people in Canada are hospitalized for pneumonia. In 2021-2022, there were over 63,000 emergency room visits for pneumonia in Canada, a substantial decrease from the numbers recorded from 2010 to 2020. Perhaps unsurprisingly, those aged 65 years and older account for the highest number of emergency room visits for pneumonia. The median length of stay for emergency department visits for pneumonia in Canada has increased in recent years, with the median length of stay around 330 minutes in 2021-2022.

The child mortality rate in France, for children under the age of five, was 412 deaths per thousand births in 1800. This means that more than forty percent of all children born in 1800 did not make it to their fifth birthday. Child mortality remained high in the nineteenth century, before falling at a much faster rate throughout the 1900s. Despite falling consistently during the last 130 years, there were two occasions where child mortality actually increased, which can be attributed to both World Wars and the Spanish Flu Pandemic. In 2020, the child mortality rate in France is expected to be just four deaths per thousand births.

The child mortality rate in Norway, for children under the age of five, was 336 deaths per thousand births in 1815. This means that approximately 34 percent of all children born in 1815 did not make it to their fifth birthday. Over the course of the next 205 years, this number has dropped drastically, particularly from 1865 onwards, and the rate has dropped to its lowest point ever in 2020 where it is just two deaths per thousand births, which is the lowest in the world. The only times where Norway's child mortality rate increased in the twentieth century was in the 1910s and 1940s, as a result of the Spanish Flu pandemic and the Second World War.