The 1918 Flu Pandemic

Lindsey Randle

MLT 2080 - Microbiology

An Introduction

- The Flu pandemic of 1890: a precursor

- The Public Health Service began requiring health reports from communities in 1918.

- Influenza wasn’t a reportable disease.

- In March of 1918 “18 cases of influenza of a severe type” from Haskell County Kansas were reported.

In Coming

- Reports of a severe flu came in from Europe.

- most young male soldiers recovered quickly but some developed secondary pneumonia of “a most virulent and deadly type”.

- “Within two months, influenza had spread from the military to the civilian population in Europe. From there, the disease spread outward”

The Beginning

– August the virus broke out in three port cities.

- Freetown, Sierra Leone

- Brest, France

- Boston, Massachusetts

- Large numbers of Boston dock workers at the Commonwealth Pier reported sick.

- By September the disease had spread to California, Florida, North Dakota, and Texas.

Three Waves

The First Wave

- A mild flu in the spring and summer of 1918

The Second Wave

- A severe flu in the fall of 1918

The Third Wave

- The spring of 1919

- 20 - 50 million people died around the world

- 675,000 dead in the United States out of a population of 105 million

- Took 3 times as many lives as WW1

Minnesota Stats.

– The first case was reported in early October 1918.

– In less than a week later “more than a thousand cases of ‘The Spanish Flu’ were reported in Minneapolis alone”.

– On October 11th the Minneapolis Department of Health ordered the shut down of many public places such as schools, churches, and theaters.

– In NE Minnesota wild fires forced mass evacuations and devastation to homes and the deaths of hundreds. This caused the further spread of the flu across the state.

Influenza A and B

- Belongs to the family Orthomyxoviridae.

- Zoonotic infection is typically carried by birds and mammals.

- The “viruses are enveloped, and types A and B have eight segments of ssRNA”.

- 2 major surface antigens hemagglutinin (H) and neuraminidase (N)

Hemagglutinin

– H antigen binds to receptors and fuses to host cell membranes

– There are 15 known H antigens

– H1, H2, and H3 are known to infect humans

Neuraminidase

- N antigen “cleaves budding viruses from infected cells”.

- There are 9 N antigens

- Human infections are caused by N1 and N2.

Influenza’s Persistence

– Today a mild flu outbreak may kill 30,000 Americans.

– “In six different years from 1972 to 1995 influenza deaths in the United States exceeded 40,000”.

– There are two ways the antigens can change.

– 1) antigenic drifts: a minor change in antigenic structure caused by RNA replication errors.

– 2) antigenic shift: a drastic change in surface antigens.

– There are two modes by which antigenic shifts occur.

Antigenic Shift

– Mechanism 1: Genetic Reassortment

– This “occurs when pieces of both influenza viruses become mixed into a viron, resulting in a new strain of influenza”.

– Mechanism 2: Adaptive Mutation

– A virus adjusts and becomes transmissible

– Results in a novel virus “against which there is little to no pre-existing immunity”

– This increases new risks for pandemics

Influenza C

– Enveloped

– Contains only 7 ssRNA segments.

– Is missing the gene for neuraminidase.

– More stable than influenza A.

– Can cause mild upper respiratory illness in humans.

Symptoms

– The virus is spread by aerosols and it attacks ciliated epithelial cells lining the respiratory tract.

– Causes necrosis and sloughing of the cells

– Incubates 1-4 days

– Symptoms include “rapid onset of malaise, fever, myalgia, and nonproductive cough”

– Fever as high as 41* C or 105.8* F

– Can cause fatal viral pneumonia including secondary bacterial pneumonia

The Spanish Flu

– Young adults were particularly targeted

– “Death rates for 15-34 year olds were 20 times higher than the previous year”

– “most deaths were caused by secondary bacterial pneumonia”

– Sickness lasted 5 days before patients were killed from a viral pneumonia accompanied by a “massive acute pulmonary hemorrhage or pulmonary edema”

The Spanish Flu

– Transmissibility “is mediated by the hemagglutinin membrane glycoprotein”

– Alterations allowed for transmission between birds and humans and then from human to human

– This shift was H1N1.

Reconstruction

– They collected cDNA fragments

– Sample was collected from a frozen lung

– The genetic code didn’t reveal any features associated with virulence.

– They needed to study an intact live replicating virus within a suitable host.

– Lab mice died in 3 days

– They found that unlike the usual seasonal flu it attacks deep in the lungs resulting in extreme inflammation

– They also found it had two H antigen mutations allowing it to spread between humans

Continued

– Infection also triggered highly sustained innate immune response

– Significant influx of neutrophils and alveolar macrophages to the lungs

– HA receptor binding specificity plays a role in pathogenesis in mice

– “Two amino acids that are responsible for receptor binding specificity and efficient virus transmission, has also been demonstrated in ferrets.”

– RNA polymerase complex is responsible for viral pneumonia

Monitoring the Flu Today

– Hospitalized Surveillance: hospitals report whenever they have lab confirmed influenza and they submit specimens to MDH-PHL for testing.

– Sentinel Surveillance: healthcare providers monitor influenza-like illnesses and fill out weekly reports.

– Long-term Facility Surveillance: report suspected or lab confirmed influenza outbreak.

– School Surveillance: K-12 schools report outbreaks when 5% of enrolled students or 3 or more students from the same classroom are absent.

– MLS Laboratory Surveillance: labs perform rapid testing for influenza and Respiratory Syncytial Virus, some preform confirmatory culture testing

– MLS Virology Laboratory Isolate Surveillance: isolates are subtyped to monitor strains and compared them to current vaccine subtypes.

Public Health Emergencies

– CDC provides funding and technical assistance to strengthen local services ability.

– Respond and support national, state, and local partners to save lives and reduce suffering by providing scientific and logistic expertise and deploying personnel to the site of the emergency

Legacy

– Two months after the pandemic started reports to the Public Health Service reduced.

– Communities began lifting quarantine and schools were re-opened and people celebrated the end of WW1.

– The summer of 1919 hundreds of thousands of Americans were dead and more were orphaned or widowed.

– The pandemic as led to continual study and observation of influenza to prevent future pandemics and to develop better vaccines.

– The use of the resurrected 1918 virus is helping scientists understand transmission from birds to humans and human to human.

– Currently they are watching the Avian flu.

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