Pandemic

Why a Global Influenza Pandemic is Not a Cause for Concern

Ted Espenschied

Background

Influenza• Influenza is an infectious

disease common to birds and mammals, caused by a family of RNA viruses

• Common symptoms of influenza include fever, sore throat, muscle ache, headaches, and respiratory impairment

• Influenza itself is not a lethal pathogen – however, when a flu patient contracts pneumonia, death can occur

Transmission• Influenza is a contagious disease that

is spread by respiratory aerosols• An infected person discharges viruses

particles with each cough or sneeze• Many healthy adults can be

contagious for up to 1 full day before they experience symptoms

• An infected individual can be contagious for up to 5 days after the onset of symptoms

Seasonality

Centers for Disease Control: Influenza: The Disease (http://www.cdc.gov/flu/about/disease.htm)

Who is Vulnerable

• Anyone can get the flu, during any flu season• People 65 and older, as well as individuals with chronic

medical conditions are especially vulnerable• Very young children (whose lungs and immune system

are not fully developed) are also vulnerable• The CDC estimates that between 5% and 20% of the

U.S. population contracts the flu every year• An average of 36,000 people die from influenza in the

U.S. every year• More than 200,000 must be hospitalized

Context

History: Past Pandemics• It is difficult to determine if past pandemics were

cause by the influenza virus• Many other diseases (diphtheria, typhoid fever, and

pneumonic plague) share similar symptoms• Most infamous epidemic: 1918-1919 Spanish Flu• Current estimates are that 50 to 100 million people

died worldwide• Extremely high infection rate - 50%• Killed between 2% and 20% of those infected (typical

flu mortality rate = 0.1%)• Unusual for influenza, this pandemic killed mostly

young adults

Avian (Bird) Flu

• Avian Influenza is an infectious disease of birds, especially domestic birds (poultry)

• There are two forms: mild (common) and extremely lethal (rare)

• Highly pathogenic forms (H5 and H7 subtypes)• Spread: wild waterfowl infect domestic flocks

with highly pathogenic H5N1 strains• Associated with heightened risk of human

exposure and infections

Avian Flu, (Cont’d)• However…• Influenza viruses are normally very species-specific

(spillover is rare)• H5N1 has the most potential to harm humans

– Has jumped species 3 times in recent history (1997, 2003, and 2004)

– Has the potential to “go global”• 2 Mechanisms for improving transmissibility to people

(jumping the species gap)– Reassortment – exchange of genes with human flu virus

during co-infection– Gradual process of adaptive mutation

So Why Shouldn’t We Worry?

Vaccinations & Treatment• According to the CDC, “the single best way to protect against the flu is to get

vaccinated each year.”– Flu Shot (good for about 6 months)– LAIV (Live Attenuated Influenza Vaccine) Nasal Spray– Each vaccine contains 3 types of virus: 2 A viruses (H3N2 & H1N1) and 1

B virus– People at high risk or people exposed to high-risk individuals– The effectiveness of the vaccine depends on the age and health of the

individual, as well as on the similarity to the virus strains in circulation• Anti-viral medication• Antibiotics (fight secondary infection, e.g. pneumonia)• The Respiratory Viruses section of The National Institute of Allergy and

Infectious Disease (part of the NIH) is developing vaccines for all 16 of the hemaglutinin proteins (the ‘H’ in HxNy) found in waterfowl virus type A

Monitoring• The CDC collects flu data year round• During the flu season, the CDC reports on

influenza ‘activity’ each week from October through March every year

• Viral surveillance (in labs across the U.S.)• Sentinel physician surveillance• Mortality surveillance• State epidemiological reports• Influenza-associated pediatric mortality and

hospitalizations• According to the website www.pandemicflu.gov,

the U.S. is at Stage 0, with no cases of domestic animal outbreaks of avian flu

• The world is at Phase 3 “No or very limited human-to-human transmission”

Julie Louise Gerberding, M.D., MPH – Director of

the CDC

Global Monitoring

• The WHO is keeping track of incidents and is characterizing the H5N1 Avian Influenza strain

• Pandemic Preparedness Plan– Reduce Human Exposure to H5N1– Strong Early Warning Systems– Intense Rapid Containment Operations– Global Capacity to Cope with Pandemic– Coordination of Global Influenza Research

Adequate Response

• The WHO has an effective response protocol for instances of highly infectious avian flu – Rapid culling– Proper carcass disposal– Quarantining and disinfection of farms– Strict “Biosecurity” (sanitary) measures– Restrictions on the movement of poultry (especially

between countries)– Vaccination (as a supplementary emergency measure)

Larger Problems• Other lethal, infectious diseases (Ebola?)• HIV/AIDS• Respiratory sincytial virus (RSV):

– Most common cause of severe respiratory illness in children

– Leading cause of death by respiratory illness in individuals >65

• In the grand scheme of things, there are far more pressing issues in the realm of global health, with respect to infectious disease as well as other health hazards

Influenza at UNC

• Flu vaccine – according to the Campus Health website, the vaccine is 75-90% effective

• The Influenza vaccine is 1 of 8 recommended vaccinations for college students (among Hepatitis A and B, HPV, Meningococcal, Mumps, Whooping Cough, and Chicken Pox)

• Campus Health provides up-to-date information to students about recognizing, preventing, and managing the flu on campus every year

Mary Covington, MD – Assistant Vice Chancellor for

Campus Health Services

Media Hype?

• Where is this bird flu? I’ve been waiting for four years now…• It’s limited occurrence has been confined to Asia and Africa,

and has never been found in the U.S.• So is bird flu the “disease of the moment?”

Evolution: 2 Perspectives

• Influenza Virus– If a strain of the influenza virus becomes too

lethal, it will eventually kill off its host species, and it too will die

– In the framework of evolution and propagation of the species, this is unfavorable

• People– A strong new driver for natural selection– An evolutionary push to become a more fit

species

Benefits?

• Environmental – reduce the human burden on natural systems

• Ecological – is the earth at carrying capacity for Homo sapiens, given our current technological advancements?

• Economic – greater availability of resources and raw materials?

Sources

• Centers for Disease Control and Prevention• National Institute of Health• World Health Organization• http://www.ifpma.org/influenza/content/images/

diagram_virus_thumb.jp• http://www3.niaid.nih.gov/healthscience/healthtopics/Flu/

default.htm• http://www.pandemicflu.gov/index.html• UNC Campus Health Services