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The influenza virus never seems to go away. This virus survives and causes

misery for us every year because of its ability to quickly mutate. It can even

incorporate genetic material from animal-sourced influenza strains to form new

ones our immune systems have never battled before.

There’s been four global influenza pandemics in

recent history, starting with the devastating

Spanish Flu of 1918 that infected an

estimated 500 million people worldwide.

This represented about one-third of the

planet’s population the early 20th

century.1 The Spanish Flu contributed to

the death of 20 to 50 million victims

worldwide, including about 675,000

Americans.1

Well over a decade ago, researchers were able to retrieve viable Spanish Flu viral

proteins from preserved, long-deceased victims and soon learned why the

Spanish Flu was so deadly: A group of three genes within the virus critically

weakened the victim’s pulmonary tissue. This rapid and severe lung damage led

to pulmonary edema or instead, offered a gateway for bacterial pneumonia to

quickly set in and cause death.2 Sir Alexander Fleming did not discover penicillin

until much later in 1928, so the bacterial pneumonia was still untreatable by

what we take for granted today: Antibiotics.

Influenza The flu season approaches: Influenza Type A and Type B viral infections

1 to 4 days from exposure

3 days to more than 2 weeks

Respiratory droplets

Gloves, N95 mask, goggles,

disposable gown or Tyvek suit.

Resides in respiratory tissue

and can be transmitted

through a cough, sneeze,

talking, or other respiratory

secretion release.

Can survive on room air

temperature surfaces for

hours to a full day depending

on the porosity of surface,

temperature, and humidity.

Use standard EMS/hospital

disinfecting solutions to clean.

Is a virus, so does not produce

disinfectant-resistant spores.

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While not as catastrophic as the Spanish Flu, the remaining global influenza pandemics that also affected the

United States included:

• The Asian flu pandemic (H2N2), which occurred between 1957 and 1958 and killed about 1.1 million

people worldwide, including some 116,000 people in the United States.3

• The Hong Kong flu (H3N2) pandemic from 1968 to 1969 killed approximately 1 million people,

including about 100,000 Americans.4

It is believed that the Hong Kong flu and the earlier Asian flu were mutations of an avian (bird) flu

virus and began spreading in the United States by infected soldiers returning home from the Vietnam

War. By that time, the virus had already spread from China to other east Asian areas, including

Vietnam and Singapore. The availability of antibiotics helped to reduce mortality from secondary

bacteria pneumonia infections, but the fatality rate was still significant. Flu pandemics tend to form

waves of increased infection, and the last wave was particularly severe on global mortality.

• Swine Flu (2009 Human H1N1): In just over a year, more than 12,000 Americans perished during

the H1N1 (or “swine flu”) pandemic that lasted 19 months. It was discovered in January 2009 and

finally reduced to sporadic (smoldering) cases in August 2010.5

This flu was a little different ---

death was more likely in those who

were younger compared to the

Asian and Hong Kong flu… usually

less than 65 years old. It was first

discovered in central Mexico and

within a few months spread to 43

countries, including the US.6

Researchers suspect that older

Americans may have developed

some faint immunity decades

before through exposure to another

influenza strain much like this one.

However, the 2009 H1N1 pandemic

did contribute to the death of

young and old alike.

In the past, a few flu strains had

already developed from a triple

reassortment of avian (bird), swine

(pig), and human flu viruses.

However, the 2009 Human H1N1

“swine flu” evolved as a novel (new)

virus when an existing

The H1N1 Swine Flu ancestry tree. The Eurasian swine viral component

combined with previous avian/swine/human influenza viruses to form

H1N1. This created a new (novel) virus and is now one of the strains

targeted by our flu vaccines. Image: Trifonov (2009).

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avian/swine/human influenza strain added genetic material from a Eurasian pig flu virus.6 The name

“swine flu” refers to this Eurasian swine addition.

Both the swine H1N1 and human H3N2 virus strains are two type A influenza viruses targeted by the

annual influenza vaccine.

The signs and symptoms associated with influenza include one or more of the following:7

• Fever or feeling feverish/chills. Presence of a fever or chills is not a requirement though.

• Cough

• Sore throat

• Runny or stuffy nose (rhinorrhea)

• Muscle or body aches; Headaches

• Fatigue (tiredness)

• Some people may have vomiting and diarrhea. This is usually more common in children.

The CDC’s chart of emergency warning signs for flu. While the flu usually resolves on its own without

complications, the warning signs above suggest a more emergent condition. Image: CDC.

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Is it just the common cold or influenza? The flu’s signs and symptoms are nearly interchangeable

with the milder common cold. Both are respiratory illnesses but caused by entirely different viruses.

Generally, the flu’s symptoms

appear rapidly, are more severe,

and can contribute to serious

health problems (pneumonia,

sepsis, myocardial injury) leading

to hospitalization or even death.

The common cold usually has a

gradual onset, is more likely to

cause rhinorrhea (runny nose),

and its symptoms are milder with

less effect on a person’s overall

health.8

Recovery from the flu usually

takes a few days to two weeks or

more. Some people may develop

complications that are short-lived

or instead, can lead to permanent

disability or even death.

Some of the complications with flu are listed below. Some are uncommon, but should remain in the back

of your mind when caring for a patient who “has the flu” but appears to be more critically ill: 7

• Sinus and ear infections

• Pneumonia (either from the flu or co-infection with an opportunistic bacterial infection)

• Myocarditis (inflammation of the heart tissue)

• Encephalitis (inflammation of brain tissue)

• Rhabdomyolysis (breakdown of skeletal muscle tissue)

• Multiorgan failure (lungs, kidneys, etc.)

• Extreme inflammatory response can lead to sepsis (hypotension as a sign, for example)

• Worsening of chronic medical conditions, such as asthma or heart failure.

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Influenza is transmitted by respiratory droplets. A person cannot acquire swine flu by eating pork or

avian flu by eating chicken or eggs. The highest risk of transmission occurs when an infected person

sneezes, coughs, or transmits respiratory secretions into the air by other means. Transmission can also

occur indirectly through contact with contaminated surfaces such as tables, pens, etc. where the virus is

then brought into the nose or mouth. However, this route is not as common compared to respiratory

droplets in the air.

The time from infection to illness (incubation

period) is about 2 days, but ranges from one

to four days.9

How contagious is it? Back in 1918

with the Spanish Flu pandemic, it’s

estimated that one person typically infected

1.4 to 2.8 others.10 More recently with the

swine flu in 2009, one person infected about 1.4

to 1.6 other people.11 This reduction was credited

towards flu vaccines and the use of antivirals that helped

lower the risk of infecting others.

With COVID-19 still a continuing threat that is not disappearing anytime soon, UMC EMS’ PPE

requirements remain at the same level for those with suspected COVID-19: Gloves, N95 mask, eye

goggles/face shield, and Tyvek suit. Both COVID-19 and influenza present similar (if not identical) signs

and symptoms, and the only true way to determine the causative agent is through diagnostic testing.

All contact surfaces must be disinfected thoroughly before returning to service. This includes the pulse

oximeter (use alcohol only), ECG cables, BP cuff(s), and stethoscopes. Door handles, the radio

microphone, and cabinet doors are easily forgotten contaminated areas.

How long can influenza survive? The influenza virus can remain viable on contact surfaces for

hours. One study that examined the viability of H1N1 swine flu influenza and found the virus survived in

an indoor-type, temperate environment for up to a few hours on porous surfaces (cloth, paper). Rarely,

it survived more than nine hours on most of the other surfaces tested. But, metallic and non-metallic,

non-porous materials (countertops and door handles, for example) posed the greatest risk with the virus

surviving up to 24 hours in some samples.12

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The annual influenza vaccination is not 100% effective. However, the Centers for Disease Control and

Prevention (CDC) also reports:

“…Flu vaccination reduces the risk of flu illness by

between 40% and 60% among the overall population

during seasons when most circulating flu viruses are

well-matched to the flu vaccine. In general, current flu

vaccines tend to work better against influenza B and

influenza A(H1N1) viruses and offer lower protection

against influenza A(H3N2) viruses.” 13

Other vaccines such as hepatitis, varicella, or tetanus are far more effective in targeting their specific

pathogen. Influenza vaccination is less effective because how our immune system responds to flu and

more importantly, one trait that allows influenza to adapt and survive well: Antigenic drift.

Antigenic drift refers to the small changes or

mutations in the genetic makeup of a virus

that inevitably alters its surface glycoproteins.

The surface proteins are called antigens,

which is what our immune system can use as

a form of identification to determine if

something is friend or foe. After vaccination

or exposure to a virus, antibodies are

developed to target specific viral antigens and

trigger an immune response.

Vaccines focus on certain unique antigens

found on a pathogen. However, the influenza

virus --- particularly type A ones --- quickly mutate and our immune system may not be able to recognize

it from a previous vaccination or infection.

Antigenic drift is also the reason why a person can be re-infected by the influenza virus within the same

year or even more frequently. Just a small yet effective change in the antigen can be enough for it to

look like something the immune system has not encountered before.

The flu vaccine is reviewed and updated yearly to try and keep up with antigenic drift. But even if a

vaccine is not a perfect match for the season’s flu, if it’s close, there could be enough antibody protection

to help reduce the severity of the signs and symptoms. Vaccination has been shown to effectively reduce

hospitalization and ICU care for those who acquired the flu even after receiving the vaccine that year.14

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Antigenic shift is different than antigenic drift. In

this case, there is an abrupt, major change in the

influenza virus. For example, if an influenza virus

from an animal population gains an ability to

infect humans, antigenic shift occurs. The 2009

swine flu is a recent case where the addition of a

Eurasian swine flu created a new H1N1 strain

unrecognizable to nearly everyone’s immune

system. This resulted in a pandemic. Fortunately,

antigenic shift does not happen frequently.

Types of flu. In the United states, influenza in

humans is usually caused by either Type A or Type

B flu. There is a Type C, which is uncommon and

presents with milder symptoms), and so is not the target of vaccination programs. Type D influenza

remains infective for animals only, particularly cattle.

Type A flu is usually implicated for both epidemics and pandemics as it quickly mutates (antigenic drift)

and can even incorporate other genetic material from vastly different flu strains (antigenic shift). Annual

vaccinations protect against two of the more common strains of Type A flu. Type B flu does not shift (it

affects humans only) and it does not drift much at all. Symptoms of Type B influenza infection may even

be milder in adults compared to Type A flu. However, it tends to develop more serious illness and

complications in children, which is why flu vaccines for healthcare providers include the two more

common Type B strains within their composition.

Vaccination recommendations. An annual flu vaccination is recommended for everyone 6

months old or older. During 2018, vaccination prevented an

estimated 4.4 million influenza illnesses, 58,000 influenza-

associated hospitalizations, and 3,500 influenza-associated

deaths in the United States alone.15

It takes about two weeks for enough antibodies to develop

after vaccination to provide protection against the flu. If

someone develops the flu a few days after vaccination, they did

not “get the flu” from the vaccine. They acquired the flu before

enough antibodies were produced to combat it. The injectable

flu vaccine does not have any viable or living flu virus that can

cause illness, so it cannot cause the flu.

Can a person be contagious before flu symptoms develop? Yes. The flu can be transmitted one day

before the infected person shows any signs or symptoms.15

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Keep in mind that some people can still become infected with a flu virus the vaccine was designed to

protect against. Protection provided by flu vaccination can vary widely, based in part on health and age

factors of the person getting vaccinated. In general, a flu vaccine works best for healthy younger adults

and older children. Some older adults and those with certain chronic illnesses may require a stronger or

double dose of the flu vaccine to account for their less-than-optimal immune system.

While the flu vaccination is not a perfect tool, it is still the best way to protect against flu infection along

with frequent hand washing, PPE, and disinfecting surfaces after each patient contact in the ambulance.

Be sure to complete the quiz and evaluation to earn credit for this education.

Please let a member of the training staff know of any questions. Thank you!

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1 1918 Pandemic (H1N1 virus). Centers for Disease Control and Prevention. Last review: March 20,

2019. Web page: https://www.cdc.gov/flu/pandemic-resources/1918-pandemic-h1n1.html.

Accessed: August 30, 2020.

2 Jordan D, Tumpey T, Jester B. The Deadliest Flu: The Complete Story of the Discovery and

Reconstruction of the 1918 Pandemic Virus. Centers for Disease Control and Prevention. Last

review: December 17, 2019. Web page: https://www.cdc.gov/flu/pandemic-

resources/reconstruction-1918-virus.html. Accessed: August 30, 2020.

3 1957-1958 Pandemic (H2N2 virus). Centers for Disease Control and Prevention. Last review: January

2, 2019. Web page: https://www.cdc.gov/flu/pandemic-resources/1957-1958-pandemic.html.

Accessed: August 30, 2020.

4 1968 Pandemic (H3N2 virus). Centers for Disease Control and Prevention. Last review: January 2,

2019. Web page: https://www.cdc.gov/flu/pandemic-resources/1968-pandemic.html. Accessed:

August 30, 2020.

5 2009 H1N1 Pandemic (H1N1pdm09 virus). Centers for Disease Control and Prevention. Last review:

June 11, 2019. Web page: https://www.cdc.gov/flu/pandemic-resources/2009-h1n1-pandemic.html.

Accessed: August 30, 2020.

6 Trifonov V, Khiabanian H, Rabadan R. Geographic dependence, surveillance, and origins of the 2009

influenza A (H1N1) virus. N Engl J Med. 2009;361(2):115-119. doi:10.1056/NEJMp0904572

7 Flu Symptoms & Complications. Centers of Disease Control and Prevention. Last update: July 2,

2020. Web site: https://www.cdc.gov/flu/symptoms/symptoms.htm. Accessed: August 29, 2020.

8 Influenza (flu). Centers for Disease Control and Prevention. Last review: December 30, 2019. Web

page: https://www.cdc.gov/flu/symptoms/coldflu.htm. Accessed: August 30, 2020.

9 Influenza (seasonal). World Health Organization. November 6, 2018. Web page:

https://www.who.int/en/news-room/fact-sheets/detail/influenza-(seasonal). Accessed: August 31,

2020.

10 Ferguson NM, Cummings DA, Fraser C, et al. Strategies for mitigating an influenza pandemic. Nature.

2006; 442:448-452.

11 Coburn, BJ, Wagner BG, Blower S. Modeling influenza epidemics and pandemics: insights into the

future of swine flu (H1N1). BMC Med. 2009; 7 (30). doi: 10.1186/1741-7015-7-30

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12 Greatorex JS, Digard P, Curran MD, et al. Survival of influenza A(H1N1) on materials found in

households: implications for infection control. PLoS One. 2011;6(11):e27932.

doi:10.1371/journal.pone.0027932

13 Vaccine Effectiveness: How Well Do the Flu Vaccines Work? Centers for Disease Control and

Prevention. Last reviewed: January 3, 2020. Web page: https://www.cdc.gov/flu/vaccines-

work/vaccineeffect.htm. Accessed: August 31, 2020.

14 Thompson MG, Pierse N, Sue Huang Q, et al. Influenza vaccine effectiveness in preventing influenza-

associated intensive care admissions and attenuating severe disease among adults in New Zealand

2012-2015. Vaccine. 2018;36(39):5916-5925. doi:10.1016/j.vaccine.2018.07.028

15 Centers of Disease Control and Prevention. Key Facts About Seasonal Flu Vaccine. Last update:

August 17, 2020. Web site: https://www.cdc.gov/flu/prevent/keyfacts.htm. Accessed: August 29,

2020.

Trifonov V, Khiabanian H, Rabadan R. Geographic dependence, surveillance, and origins of the 2009

influenza A (H1N1) virus. N Engl J Med. 2009;361(2):115-119. doi:10.1056/NEJMp0904572

Flu Symptoms and Complications. Centers for Disease Control and Prevention. Last review: July 2, 2020.

Web page: https://www.cdc.gov/flu/symptoms/symptoms.htm. Accessed: August 31, 2020.