Download Virus notes (H1N1)

Understanding Viruses
Reminder: EOC Monday
Virus chapter – Chapter 24
What is the H1N1 virus?
The current swine flu outbreak is
caused by a new swine flu virus
that has spread from person to
person -- and it's happening among
people who haven't had any contact
with pigs. Here is a picture of the
new swine flu virus, colorized and
magnified
Virus
Nucleic acid – DNA or RNA
Protein coat (capsid)
Envelope in some – bilipid
membrane from host cell that aids in
virus recognize cells to infect
What’s in a name?
Letters represent 2 proteins on surface
of virus:
H – hemagglutinin
N – neuraminidase
Numbers refer to slight variations in
The form of each protein
the variations are significant b/c
Our immune system has to recognize them
Symptoms:
Fever
Cough
Sore throat
Body aches
Headache
Chills
Fatigue
Need lab test to determine if it is really
H1N1
Prevention:
Direct contact
Touching an object they recently touched
Flu germs start spreading up to a day
before symptoms start, and for up to
seven days after getting sick
Treatment
Sensitive to antiviral drugs Tamiflu and
Relenza
Most effective when taken within 48 hours
Of the start of flue symptoms
Most people do not need drugs
A new vaccine will take 4-6 months to mak
Viruses


Viruses are not living
organisms
They are particles of
nucleic acid, proteins,
and lipids that
reproduces only by
infecting other
organisms
Viruses

The typical virus is
composed of a core
of either DNA or RNA
surrounded by a
protein coat

Influenza Virus


Viruses are very specific in the cells they
infect
Plant viruses do not infect human cells;
most animal viruses only infect certain
animals.
Infections

Two ways:

1) Lytic infection: a virus enters a cell, makes
copies of itself, and causes the cell to burst,
thus spreading the virus

2) Lysogenic infection: a virus embeds it’s
DNA into the host’s DNA and replicates along
with the host cell’s DNA
Avian Bird Flu

Then why are people
worrying about the
Avian bird flu if only
birds get it?
Herpes
HIV

1.
2.
3.
4.
To make your plates follow these directions.
Put one name on plate, date, hour
Section off your petri dish into 4 sections, #
the inside corners.
#1 is your control
Pick 3 things to sample to determine if
bacteria is present.
Sample area with tape.
Headlines
China confirms third person dead from H5N1 bird flu strain
China confirmed its third human death from bird flu yesterday, saying a
41-year-old woman from the country's southeast succumbed to the
virulent H5N1 strain. (Dec 30, 2005)
HHS chief urges states to prepare for bird flu
Health and Human Services Secretary Michael O. Leavitt urged each state
yesterday to prepare for the possibility of a deadly avian flu pandemic by
holding planning summits within four months. (Dec 6, 2005)
Bird flu spreads in China, Indonesia
BEIJING // China announced yesterday the spread of bird flu to a far
western region, while Indonesia reported its first outbreak in the tsunamiravaged Aceh province, where hundreds of chickens have died of the
disease. (Nov 25, 2005)
What is H5N1?
H5N1 Flu is a highly pathogenic strain of avian influenza (bird flu),
first recorded in Hong Kong in 1997.
Normally: non lethal, carried worldwide by wild bird populations in their
intestines.
Problem: this variant has mutated(changed) into the most fatal strain of avian
influenza.
Normally: this virus would not be harmful to humans.
Problem: close proximity of humans to live chickens, pigs, and other animals, like on
farms or marketplaces could cause the H5N1 virus to exchange genetic material with
other viruses that more easily attack humans… it changes
Problem: the H5N1 strain may jump the species barrier and cause severe disease, with
high mortality, in people. It is feared that the H5N1 subtype could trigger the next
pandemic.
The H5N1 virus could either:
•adapt, giving it greater affinity for humans, or;
•exchange genes with a human flu virus, thereby producing a completely new virus strain
capable of spreading easily between people, and causing a pandemic.
Fighting Fire with Fire
Fighting the deadly H5N1 flu virus may be done by using reverse genetics, where the
virus's genes are rearranged in a lab to make a new strain.
At the Core: Influenza viruses are constantly evolving (or _________) with eight
genetic segments at their core that carry the instructions for replication.
On their surface, they have two different types of protein spikes.
1. the hemagglutinin (HA), makes a virus stick to a cell to cause infection.
2. neuraminidase (NA), allows newly formed viruses to leave the host's
cells.
How vaccines work: When vaccinated, the human immune system makes antibodies
that recognize these surface protein spikes. Then, when a virus with the same types of
spikes tries to cause infection, the antibodies attach to the invader's spikes and fight it
off.
Great Idea!:To develop the H5N1 "seed strain" for making the first pandemic vaccine,
scientists take the surface protein spikes of the bird flu virus (H5 and N1) and put
them together with the genetic material of a harmless, master strain that's been used
for decades to produce flu vaccines.
How the virus spreads…
through saliva, nasal secretions, and feces,
other birds may pick up the virus through direct contact with these excretions or
when they have contact with surfaces contaminated with this material
The H5N1 virus is likely to spread throughout the world since migratory birds are
some of the carriers of the virus.
Past outbreaks of avian flu have often originated in crowded conditions in
southeast and east Asia, where humans, pigs, and poultry live in close quarters.
The virus is more likely to mutate into one that infects human under such
conditions
Q. What does it mean when scientists say the bird flu will evolve?
Answer: It will CHANGE OVER TIME!
Why are bacteria once controlled by penicillin
becoming resistant to every antibiotic known?
1. They just don’t make antibiotics like they used to.
2. Doctors aren’t diagnosing illnesses properly.
(They don’t make doctors like they used to.)
3. Pharmacies are dispensing cheap drugs.
(They don’t make pharmacists …)
4. Medicine and agriculture make antibiotics part of
the environment, so pathogens evolve drug
resistance through natural selection.
Why are bacteria once controlled by penicillin
becoming resistant to every antibiotic known?
1. They just don’t make antibiotics like they used to.
2. Doctors aren’t diagnosing illnesses properly.
(They don’t make doctors like they used to.)
3. Pharmacies are dispensing cheap drugs.
(They don’t make pharmacists …)
4. Medicine and agriculture make antibiotics part of
the environment, so pathogens evolve drug
resistance through natural selection.
So it isn’t surprising that mass
media miss the boat
ALMOST ENTIRELY
Pathogens, parasites and hosts participate in
two classes of interactions.
1. Evolutionary change in two contexts:
a. change over time in the classic sense
b. co-evolutionary relationships with hosts and
their immune systems
2. Ecological interactions in two contexts:
a. within the host’s body (“host as environment”)
b. among multiple hosts and environments
EVOLUTIONARY THEORY helps us understand
new and emerging diseases because:
1. MICROEVOLUTIONARY CHANGES
EXPLAIN:
evolution of drug resistance, successes and failures of
vaccines, and evolution of host resistance.
2. “MEDIUM” EVOLUTIONARY CHANGES EXPLAIN:
how pathogens jump from one host to another.
AIDS, SARS, influenza, and malaria)
(Ex:
3. MACROEVOLUTIONARY CHANGES EXPLAIN:
how particular pathogens come to affect certain hosts
over long periods of time.
An evolutionary perspective also makes it
clear that ecological principles are essential
to understanding what’s happening with
infectious diseases.
Why?
Because …
ECOLOGY DRIVES NATURAL SELECTION.
(host as environment, medication, population
growth, other ecological variables)
HUMAN POPULATIONS GROW & MIGRATE.
Changes in “human ecology” - the way we live, the
ways we produce our food, etc., - alter host/parasite
interactions.
GLOBAL CLIMATE IS CHANGING.
Climate affects ecological relationships between
humans, other animals & plants, and pathogens.
Why are so many new and emerging diseases
these days?
In large part because modern civilization is changing
the ways that human populations, domestic animal
populations, and wild animal populations interact.
Why are so many new and emerging diseases
these days?
In large part because modern civilization is changing
the ways that human populations, domestic animal
populations, and wild animal populations interact.
The evolution of drug resistance shows the
relationship between evolution & public
health.
Alexander Flemming warned that overuse of
penicillin would drive evolution of resistant
bacteria. Antibiotic resistant bacteria now pose
serious threats to public health.
But did anyone listen to him? Or to evolutionary
biologists who amplified his warning?
In the same way, and for the same reasons,
viruses can also evolve drug resistance.
That’s why Darwinian theory is crucial to
understanding challenges to development of
either cures for, or vaccines against, HIV.
Clip: Mutation and HIV from PBS
Evolution Project
Show 1: Darwin’s dangerous idea
Evolutionary thinking is also useful in tracing the
history of H.I.V. Where did this deadly virus come
from?
You’ve probably heard “Africa” -- but how?
After HIV was identified, researchers discovered that
many primate species in Africa are infected by similar
viruses. Applying the same kind of genetic analyses used
to construct evolutionary trees on a large scale,
researchers examined the genes of these retroviruses to
build their family tree.
The results were fascinating
The “bushmeat hypothesis” is interesting …
But is it supported by any data?
For years, transmission of retroviruses from
apes to humans was known only in laboratory
and zoo environments.
But then …
We now introduce an important term:
ZOONOSIS.
Definition:
“A zoonosis is any disease and/or infection
which is naturally transmissible from
animals to man."
Can you think of any zoonotic diseases in
the news in recent years?
(Mad Cow, Influenza, West Nile Virus,
Lyme Disease, SARS, Ebola)
Take influenza, as a “hot” example.
Until recently, most of us thought of “the flu”
as a strictly human disease.
NOT ANY MORE!
As the disease established itself and
spread across Asia, the CDC and WHO
stepped up efforts to understand how it
was transmitted - among birds and from
birds to people.
Then, just as researchers began to think
that domestic poultry were the main
problem, H5N1 began to spread among
several species of wild birds.
And because some of those species are
migratory, the virus has rapidly gone
global, following the seasonal travels of
the birds that carry it.
Of course, birds aren’t the only thing that
flies around the world these days, and
therefore aren’t the only means by which the
virus can spread around the world.
Meanwhile birds aren’t the only
animals affected by this epidemic.
Because as various bird flu strains are spreading
and reproducing in millions of wild and domestic
birds, they are also mutating … in potentially
dangerous ways.
So ... what DO we know for certain?
That the bird flu epidemic is
dangerous because the
influenza virus is evolving!
(Which is good news for viruses, but
could mean trouble for us.)
Why are some flu strains just a
nuisance, while others are dangerous?
Because of the way our immune system
identifies and attacks pathogens.
What happened?
Can it happen again?
The answers relate to the nature of influenza
as an evolving zoonosis -- and a phenomenon
we could call “viral sex.”
Why is this zoonosis so important?
Because although all influenza strains belong to
the same viral “species,” some populations are
reproductively isolated from each other in different
hosts.
This isolation means that not all strains have the
same kind of genetic variation.
And that variation can spell trouble for the human
immune system.
There are actually three parallel routes, any
or all of which could transform the current
situation into a deadly pandemic.
What’s the quick summary of what we
know so far?
The 1918 flu virus appears to have jumped,
directly, from birds to humans.
That jump, high virulence, and human-human
transmissibility appear to be dependent on a small
number of changes in the flu genome.
Certain evolving strains of the current H5N1 avian
flu strains have accumulated 5 of an estimated 10
mutations related to human-human infectivity.
What’s are some highlights of stuff we
DON’T know (yet)?
What is the likelihood that H5N1 evolution will
produce a form that efficiently infects humans?
What is the likelihood that H5N1 evolution will
produce a form that transmits efficiently from
human-human?
Can we produce a “universal” flu
vaccine?