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Influenza
• Highly contagious, potentially serious viral infection of the nose, throat, and lungs. Transmissible through human-to-human contact via aerosols• Seasonal influenza affects more than 60 million
individuals in the US every year. • High fever that begins suddenly, muscle/body aches,
chills, fatigue. • In some cases severe complications like pneumonia. • In US annually, > 200,000 individuals are hospitalized
and between 3,000-49,000 die from influenza-related complications.
Origin of influenza• Most seasonal influenza originates in Asia where there is
high density of animals and humans in close proximity• Pigs, domestic birds are major zoonotic reservoir
CAFOs (concentrated animal feed operations)
• Crowding pigs or poultry, especially when they are genetically homogenous, may increase the potential for influenza viruses to infect them• Once pigs in a CAFO
become infected, influenza viruses may swap strands of genetic material
• Influenza can travel globally and evolve in a short amount of time
How the flu virus works• Virus contains RNA• Virus enters thru epithelial cells in
respiratory tract• RNA inserted into nucleus • Polymerases in nucleus used to
make copies of viral RNA• These copies of RNA leave the
epithelial cells to infect another person
• Seasonal component due to closer contact among humans in winter and drying of epithelial cells due to dry warm air
• Vaccines can be designed for seasonal influenza
Types of seasonal influenza
• Three basic types of influenza viruses: A, B, and C. • Influenza B and C viruses are specific to humans only
(spread via human to human transmission)• Influenza A viruses infect humans and nonhuman hosts
like birds and pigs (spillover from nonhuman to human hosts). Can be highly pathenogenic.• Epidemics of seasonal influenza occur due to influenza
A or B viruses.• Only A viruses are known to cause global pandemics
Naming influenza A viruses (H1N1, H3N2…)• H and N refer to hemagglutinin and
neuraminidase.• Two main proteins on the outside of the
virus• Referred to as ‘antigens’ because they are
the structures to which our immune system responds. • Antigens are categorized according to
antibodies that respond to them. • There are 18 known hemagglutinin
subtypes for influenza A (H1 to H18) and 11 known neuraminidase subtypes (N1 to N11).
Vaccinations for influenza
• Flu vaccination is a preventative stimulation of your body to produce antibodies to a particular combination of H and N subtypes predicted to be abundant during flu season• 2014-2015 flu season
vaccinations designed to stimulate antibody production to respond to an A-type H1N1 virus, an A-type H3N2 virus, and a B virus.
Influenza A has a high potential to evolve• In a single host, the viruses remain relatively
unchanged, showing minimal evolution over extended periods.• After transfer to a new type of avian or mammalian
host, influenza viruses can undergo antigenic drift• Vaccines may not work, no immunity among
humans because virus is novel
Antigenic drift
• Change in single amino acid in a H or N protein• These may alter the: •Manner influenza is transmitted• Ability of our bodies to recognize the
virus and defend itself with antibodies• Pathogenicity of the virus
• 18 x 11 = 198 possible pairings at present
Influenza A has a high potential for pandemic• Under the right
conditions, pathenogenic A viruses can acquire ability to pass from human-to-human
Spanish Influenza of 1918
• Human-to human transmission after jumping from avian reservoir• Virus is
related to a influenza A (H1N1) virus
Spanish Influenza of 1918• One third of Earth’s population infected• 50-100 million deaths worldwide• 675,000 deaths in the United States with unusually
high death rate among healthy adults 15 to 34 yrs
A H1N1 2009
• Another human-to-human transmissible influence A virus• World Health Organization declared its first ever public
health emergency of international concern• CDC stopped counting cases and declared the outbreak
a pandemic.• Joining of three previously unacquainted influenza viral
strains• Contained genes of swine influenza from two
continents, as well as genes from strains of human and avian influenza viruses
A H1N1 2009
• Began in Veracruz Mexico• Same virus type as Spanish
Influenza• Impacted young more than
old who have had more influenza exposure• After its first year, killed an
estimated 280,000 people and sickened about 1 in 5 people worldwide 250,000 mostly in Africa and Southeast Asia
Avian influenza – H5N1
• Outbreaks of H5N1 in waterfowl, poultry, and humans have been confined to Asia
Avian influenza – A H5N1
• Migratory waterfowl were the main reservoir • H5N1 discovered in 1996 -1997
during geese die-off and first jumps from poultry to humans• 50 – 60% mortality rate, very
pathogenic• No human-to-human
transmission (although a few cases have been suggested)
Avian influenza – A H5N1
• Killed millions of poultry in Asia directly or through enforced culling.• Other large financial and
economic costs• Vaccinating poultry against bird
flu • Vaccinating poultry workers
against human flu• Increasing farm hygiene • Reducing contact between
livestock and wild birds • Reducing open-air wet markets
Can migratory waterfowl distribute H5N1 globally?
• Emergence of H7N9 virus led to closing of poultry markets and culling• No person to person
transmission• Not highly
pathogenic
A H7N9 2013
Politics of influenza
• Because many influenza viruses originate in China, country is under international pressure to identify, announce, and contain outbreaks• China criticized for
taking 27 days to announce first H7N9 cases
• H5N1 has been more lethal but H7N9 is evolving rapidly• Monitoring H7N9 virus
difficult because poultry farmers resist testing because a positive test forces them to destroy flocks that appear healthy. • A few cases of human-to-
human transmission of H7N9 virus within families• H7N9 could easily become
global pandemic
H7N9 vs H5N1
Influenza in your future:
• A global pandemic at some point seems likely, right now (2015), unprecedented diversification of influenza viruses in wild and domesticated birds, particularly in H7N9, which could become more pathenogenic• Generic pandemic scenario: human infected by
human flu virus and an avian flu virus simultaneously, allowing the pathogencity of avian flu to acquire the ability to be spread via human-to-human contacts instead of bird-to-human.
Mosquito-borne diseases
• Malaria, dengue, Chikungunya• Of the millions of
insects, only a tiny fraction of them, less than 1%, are pests. A vast majority are beneficial to humans
Plasmodium is endemic to humans yet has the potential for new spillovers
• Plasmodium jumped from gorillas to humans at some time in the past, estimated at 10,000 years ago• Plasmodium knowlesi, primarily infect macaques
but has made jump to humans and can now spread from human to humans• Plasmodium gaboni identified in chimpanzees but
has not yet jumped to humans
Malaria prevention
• 198 million cases in 2013; 584 000 deaths • 90% of deaths occur in Africa• Children < 5 yrs account for 78% of deaths.• Plasmodium falciparum malaria accounts for more
than 90% of all deaths.• Recent successes• Areas exist where interventions have interrupted endemic
transmission • Since introduction of bed nets and drugs, malaria rates
have fallen (30% in Africa since 2000)
Nonlocal malaria
• Malaria can be spread by human mobility and global travel• Even in places where malaria has been eliminated,
an outbreak can start when a traveler is infected in a foreign country and then returns home and bitten by a mosquito • Cases in US and Florida
Nets and improved detection• Free bed nets to
protect sleeping children • Health workers trained
to find malaria cases and offer tests and treatment at no charge
Drug prevention and treatment
• Chloroquine (older drug)• Artemisinin-
based combination therapy (newer)• Parasite
resistance to artemisinin been detected in southeast Asia
Drug prevention and treatment
• Chloroquine (older)• Artemisinin-based combination therapy (newer)
Mass treatment of malaria
• 50% rates of infection in some locations• Healthy-appearing carriers•Mass administration of drugs at once could
have larger impact on disease reduction• Difficult to fund and organize at large scale
Prophylactic seasonal malaria chemoprevention (SMC)
How will climate change impact the distribution of malaria?
• Climate change is not just changes in temperature, but also changes in rainfall and humidity and how these variables coincide spatially and temporally• This complexity intersects
with life cycle of the mosquito• Warmer = more
mosquitoes = more malaria is simplistic
• Small shift in where malaria occurs with no large increase in cases, other studies indicate high uncertainties• However, other mosquito-born diseases emerging:
dengue and chikungunya
