Bio II Chapter 21

What is a viruses "host range"?

A virus' host range is the range of cell types and host species a virus is able to infect.

Virulence

Ability to produce disease

Are flaviviruses RNA or DNA?

RNA

Is Ebola an RNA or DNA virus?

RNA

Is the flu an RNA or DNA virus?

RNA

How do RNA viruses replicate?

RNA-dependent RNA polymerase

Why are viruses "obligate intracellular parasites"?

Since viruses are obligate intraellular parasites, the term conveys the idea that viruses must carry out their reproduction by parasitizing a host cell. They cannot multiply outside a living cell, they can only replicate inside of a specific host.

Can you treat viruses with antibiotics?

Antibiotics do not work on viruses, such as those that cause colds, flu, bronchitis, or runny noses, even if the mucus is thick, yellow, or green. Antibiotics are only needed for treating infections caused by bacteria, but even some bacterial infections get better without antibiotics.

What three processes contribute to the emergence of viral diseases?

(1) introduction of a viral pathogen into a new host species, (2) establishment of the pathogen in the new host, and (3) dissemination of the pathogen among a large number of individuals of the new host species to bring about outbreaks, epidemics or pandemics.

What % of the population needs to be vaccinated for herd immunity to apply to a population?

(70%) A vaccine for the virus that causes COVID-19 would be an ideal approach to achieving herd immunity. Vaccines create immunity without causing illness or resulting complications. Herd immunity makes it possible to protect the population from a disease, including those who can't be vaccinated, such as newborns or those who have compromised immune systems. Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection.

What was the estimated IFR of the flu last season?

137.6(hospitalization rate) (34,200 deaths during the 2018-2019 influenza season.)

What are the candidates for the source of viral genomes?

Plasmids and transposons

How many deaths per 100,000 individuals in the population did the flu cause in 2019?

2.0

Deaths per 100,000 population

A basic measure of disease frequency is a rate, which takes into account the number of cases or deaths and the population size. For example, if a cancer incidence rate is 500 per 100,000, it means that 500 new cases of cancer were diagnosed for every 100,000 people

Zoonotic disease

A disease communicable from animals to humans under natural conditions; also know as zoonosis

Emerging disease

A disease that is caused by new or reappearing infectious agents that typically exist in animal populations

Viral envelope

A membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome. (protection)

What is a virus?

A tiny, nonliving, particle that enters and reproduces inside a living cell

Lysogenic

A viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

How does the size of viruses compare to those of prokaryote/eukaryote cells?

A virus is about ten times smaller than a typical bacteria cell, and at least 100 times smaller than a typical eukaryotic cell. A virus is about ten times smaller than a typical bacteria cell, and at least 100 times smaller than a typical eukaryotic cell. Viruses are much smaller than prokaryotes, ranging in size from about 20-300 nanometers (nm), though some can be larger. ... It is a tiny particle much smaller than a prokaryotic cell.

Bacteriophage

A virus that infects bacteria

How are IFR and CFR different?

CFR is the ratio of the number of deaths divided by the number of confirmed (preferably by nucleic acid testing) cases of disease. IFR is the ratio of deaths divided by the number of actual infections with SARS-CoV-2.

How do viruses damage or kill animal cells?

Cells that protect you and kill off the virus end up killing healthy cells in the process. This can also make us sick. Some viruses put their genetic material into the genetic material of the animal's cells. This can make animal cells misbehave and become cancerous.

What components make up a virus?

DNA or RNA and a protein coat

Which viruses that we discussed are members of the flavivirus family?

Dengue fever. Hepatitis C. Japanese encephalitis. Kyasanur Forest disease. Murray Valley encephalitis. St. Louis encephalitis. Tick-borne encephalitis. West Nile encephalitis.

Re-emerging disease

Has been present in location in past and was considered eradicated or controlled.

Capsomeres

Identical protein subunits that spontaneously self assemble to form the capsid

How does the antiviral Tamiflu work?

It works by attacking the flu virus to keep it from multiplying in your body and by reducing the symptoms of the flu. Tamiflu can sometimes keep you from getting the flu if you take it before you get sick.

What does Ro need to be in order to cause a decline in spread and for the virus to eventually go out of circulation

Less than 1

How are flaviviruses transmitted?

Most of these viruses are primarily transmitted by the bite from an infected arthropod (mosquito or tick), and hence are classified as arboviruses

Why does the effectiveness of the flu vaccine vary from year to year?

Mutations, The virus rapidly changes due to antigenic drift, a slight mutation in the virus that causes a new strain to arise.

Is a virus a cell?

No because is doesn't have all the organelles

Do we consider viruses to be alive?

No. Viruses are not made out of cells, they can't keep themselves in a stable state, they don't grow, and they can't make their own energy.

How does the percentage of population that needs to be vaccinated for herd immunity to be achieved differ according to the viruses Ro?

Often, a percentage of the population must be capable of getting a disease in order for it to spread. This is called a threshold proportion. If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold. What percentage of a community needs to be immune in order to achieve herd immunity? It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread. For example, the measles is a highly contagious illness. It's estimated that 94% of the population must be immune to interrupt the chain of transmission

Capsid

Outer protein coat of a virus

Pandemic vs Epidemic

Pandemic is a world wide spread of a disease and epidemic is a regional outbreak of disease (upper Midwest influenza outbreak)

Lytic

Pertaining to destruction

What is Ro?

The basic reproduction number, R0, is defined as the expected number of secondary cases produced by a single (typical) infection in a completely susceptible population. It is important to note that R0 is a dimensionless number and not a rate, which would have units of time−1.

What component attaches the phage to the host and injects the phage DNA inside?

The head contains double stranded viral DNA, which is ejected into host cells in order to propagate the viral infection (2). The tail connects to the baseplate, which attaches to long and short tail fibers responsible for recognizing host cells and then anchoring the phage to the host cell (4).

Infection Fatality Rate

The number of individuals who die of the disease among all infected individuals (symptomatic and asymptomatic)

Prevelance

The number or proportion of cases of a particular disease or condition present in a population at a given time.

Case Fatality Rate

The proportion of persons diagnosed with a specific disease who die from that disease

How do vaccines work?

The vaccine inserts dead or weakened pathogen to produce a primary immune response

How is the range of the Aedes aegypti mosquito going to change in the next few decades? Why is that relevant for us in Texas?

They are the main type of mosquito that spread Zika, dengue, chikungunya, and other viruses. Because Ae. aegypti mosquitoes live near and prefer to feed on people, they are more likely to spread these viruses than other types of mosquitoes. Areas with past outbreaks of chikungunya and dengue are considered at higher risk for Zika. These include U.S. territories like Puerto Rico, the U.S. Virgin Islands, and Guam. Local outbreaks have also been reported in parts of Hawaii, Florida, and Texas.

Deliberately emerging disease

Those that are intentionally introduced.

DNA viruses

Usually double stranded (ds) but may be single stranded (ss) Circular or linear

RNA viruses

Usually single stranded, may be double stranded, may be segmented into separate RNA pieces

How do DNA viruses replicate (what are the steps)?

Viral replication involves six steps: attachment, penetration, uncoating, replication, assembly, and release. ... During uncoating, replication, and assembly, the viral DNA or RNA incorporates itself into the host cell's genetic material and induces it to replicate the viral genome.

Did viruses appear before or after the first cells? Why do we think it happened that way?

Viruses did not evolve first, they found. Instead, viruses and bacteria both descended from an ancient cellular life form. But while - like humans - bacteria evolved to become more complex, viruses became simpler. Today, viruses are so small and simple, they can't even replicate on their own.

What is herd immunity?

When a majority of a population are vaccinated against a disease. This means that even people who have not been vaccinated are less likely to get it because there are fewer people to catch it from.

Are Ebola, West Nile, Zika, Dengue Fever zoonotic diseases?

Yes