Virology Lectures 2020 #12: Infection Basics

This course now moves from explaining virus infection in cell culture to a discussion of viral pathogenesis, the process by which viruses cause disease. In this lecture we cover fundamental aspects of how viruses enter hosts, spread to and infect different tissues, transmission to new hosts, and how geography and season may affect virus infections.

[peppigue]

Thanks to everyone who looks up proper info like this! We're all in this together, and every person who acquires more scientific knowledge about anything contributes to our collective prosperity.

[yahyaable]

This channel is priceless, this gentleman knows what he is saying, amazing stuff hats off .

[markdezuba]

I am an insurance agent in Colorado. I am inquisitive and I came across your lectures. I very much appreciate your presentations. So much mis information and poor public policy decisions are affecting many people. I wish the politicians would listen to your lectures before making public policy edicts. I believe I had the corona virus however my body did it’s immunological job and I was back to normal in two days.

[twothumbs]

These lectures are pure gold. The slides, explanations, pace, and thoughtful commentary are amazing. I’d put this professor in the top 1%. Thank you, sir, for posting these for everyone to enjoy and learn from.

[rbkuwar]

I am big fan of prof. Racaniello. He is an excellent teacher . I took virology in my college around 20 years ago and now I am going to update my knowledge of virology.

[wyattpershing]

Thank you for the content you post! I found your page five minutes ago and I’m so glad someone as knowledgeable as you puts information out there for people like me to find. PLEASE keep up the good work, you have no idea the positive impact you are making on this world. 🙏🏻

[questella]

Thank you for each and every one of these! 💗🥂

[doncrownover]

"Soap and Water" more effective than alcohol. I heard this from another study also.

[mateusvitorino]

The best explanation os mortality and fatality! Thanks

[kedarpol]

Transposons is one way of triggering off viruses in evolution ... Can u give a link for more information on other sources

[John-hjed]

I think what you define as the definition of Incidence is really prevalence (actual number of cases at a point in time). Incidence is the rate at which the infections are occurring...

[everybot-it]

There are seasons in the tropics. They have the so called "rainy season".

[shougatabose]

Sir, In the lecture you said, CoV-2 is transmitted during incubation period. Its not transmitted during disease?

[MrOzzyCam]

Professor Racaniello, wouldn't it be fair to say that to derive a more accurate case fatality ratio that we should look at factoring the lag time between the number of cases you have, to the time it takes for a fatal outcome to get a more accurate figure? If say with cases of COVID 19, it takes 3 to 6 weeks from case detection to a fatal outcome but you are adding 400 to 800 cases in a day as South Korea was, that you will get a skewing effect, giving an apparently lower CFR, than you actually have, especially with South Korea's highly effective drive through testing and screening protocol? If you therefore calculate today's accumulated cases against today's accumulated fatalities, you are seeing many cases that will die or recover much later. Case in point, currently South Korea has 7869 cases against 66 deaths, giving a current CFR of 0.83%, if they have found all their cases, which they haven't but assume they did, they still have 7, 470 active cases and 54 serious/critical cases, wouldn't we have to wait for those cases to either resolve by recovering or dying before we could calculate an accurate case fatality ratio? I have noticed since their case detection numbers have slowed that the CFR has gone up considerably over time as fatalities from older cases have caught up. I do understand that there are going to be a percentage of asymptomatic cases that haven't been detected, that make the CFR look higher than it is too.

[racanet]

Here are some definitions from Gordis´Epidemiology 5Th Ed, that could be useful to explain this concepts in future lectures: “The incidence rate of a disease is defined as the number of new cases of a disease that occur during a specified period of time in a population at risk for developing the disease.The critical element in defining incidence rate is NEW cases of disease. Incidence rate is a measure of events—the disease is identified in a person who develops the disease and did not have the disease previously. Because the incidence rate is a measure of events (i.e., transition from a non-diseased to a diseased state), the incidence rate is a measure of risk


Prevalence is defined as the number of affected persons present in the population at a specific time divided by the number of persons in the population at that time, that is, what proportion of the population is affected by the disease at that time? For example, if we are interested in knowing the prevalence of arthritis in a certain community on a certain date, we might visit every household in that community and, using interviews or physical examinations, determine how many people have arthritis on that day. This number becomes the numerator for prevalence. The denominator is the population in the community on that date.
What is the difference between incidence and prevalence? Prevalence can be viewed as a snapshot or a slice through the population at a point in time at which we determine who has the disease and who does not. But in so doing, we are not determining when the disease developed. Some individuals may have developed arthritis yesterday, some last week, some last year, and some 10 or 20 years ago. Thus, when we survey a community to estimate the prevalence of a disease, we generally do not take into account the duration of the disease. Consequently, the numerator of prevalence includes a mix of people with different durations of disease, and as a result we do not have a measure of risk. If we wish to measure risk, we must use incidence, because in contrast to prevalence, it includes only new cases or events and a specified time period during which those events occurred.”

[juanzalamea]

hi thanks for the video, is bogotá Colombia not Columbia ( seasonal chart of polivirus)

[sohaabdelmwgodabdelazeem]

I need to ask a question
When we can say the word infection or disease is it when we see the symptoms or just when the virous enter the body?
Actually I need an answer for this question ...can viroses cause infection or disease during there incubation periods? and if they do I want some examples..please

[Artbyevelyn]

This lecture was made right before the country was closed due to COVID-19, then delta variant and now new one omicron 🙄

[vkoptchev]

CFR should not be fatalities over infected, but fatalities over (deceased + cured). It is a logical fallacy to include Infected patients with no outcome in the denominator.

[nazishmoosakhan]

Will you plz upload lecture on why virus can to be killed easily?