L16. Human impact: disease

Question 1

what is a disease?

Answer 1

an abnormal condition that negatively affects the structure or function of part or all of an organism, and that is not due to any external injury

Question 2

types of causes

Answer 2

• airborne: caused by pathogens transmitted through air
• foodborne: consumption of food contaminated with pathogenic bacteria, viruses or toxins
• lifestyle: disease that appears to increase in countries that become more industrialized and where people live longer. Also in places which diet is high in unhealthy foods and/or sedentary lifestyle
• non-communicable: disease that cannot be spread directly from one person to another
• infectious: illness resulting from infection, presence and growth of pathogen in host organism

Question 3

Parasites vs. Pathogens

Answer 3

• parasite: an organism that lives on or in a host organism and gets its food from or at the expense of its host
• pathogens: organism that cause disease within their host
• parasites can be pathogens

Question 4

epidemic

Answer 4

widespread occurrence of an infectious disease in a community at a particular time

Question 5

Disease and humans

Answer 5

• humans have suffered from disease for million of years
• driver of community structure (humans constantly created new ways of living and eating, and genetic changes evolved to minimize the effects of these diseases

Question 6

Epidemic

Answer 6

widespread occurrence of an infectious disease in a community at a particular time

Question 7

Aboriginal people and the arrival of Europeans

Answer 7

• when Europeans began arriving on the shores of the Americas, the diseases they brought with them diseases that set off one of the largest depopulations in human history
• aboriginal populations were drastically reduced by epidemic disease over the course of the next 400 years, as Europeans continued to explore new territory and came into contact with different communities
• smallpox was the worst

Question 8

Black Plague

Answer 8

• one of the most devastating epidemics in human history resulting in the deaths of an estimated 75 to 200 million people in Europe and Asia
• estimated to have killed 30-60% of Europe’s total population
• took 200 years for the world population to recover to its previous level
• caused by a bacterium that circulates among wild rodents where they live in great numbers and density. that organism is transmitted to humans by fleas that have fed on infected rodents
• originated in Asia, rats left their habitats due to climate fluctuations
• rising standards of living after the epidemic: better living conditions and people were healthier

Question 9

Influenza

Answer 9

• commonly known as the flu, an infectious disease caused by a virus
• have been 9 influenza pandemics during the last 300 years (spanish flu being the worst, but because timing close to WWI)
• constantly mutating

Question 10

Spanish flu

Answer 10

• infected 1/3 of worlds population
• not more aggressive than any previous influenza, but that the special circumstances of the epidemic promoted bacterial superinfection that killed most of the victims
• called spanish because spain was neutral in war and reported on disease
• brought women into the work face because more men died

Question 11

Malaria

Answer 11

• mosquito-borne infectious disease that affects humans and other animals
• caused by a parasite in insects
• mosquito bite introduces the parasite from mosquito’s saliva to person’s blood
• travel to liver and reproduce
• symptoms are fever, tiredness, vomiting, and headaches
• climate change is making it spread farther

Question 12

Malaria and Panama Canal

Answer 12

• the control of malaria was vital for the construction of the Panama Canal
• US wanted to build canal but malaria was such a problem in the area it was hard for the workers to not die while working
• plan to rid the isthmus of mosquitos and their breeding sites became one of the largest sanitation campaigns ever
• plan worked, barrier of disease had been removed and the Panama Canal was completed in 1914

Question 13

Virulence

Answer 13

pathogen’s ability to infect or damage a host

Question 14

Evolution of Virulence

Answer 14

• if the host’s illness prevents the host from coming into contact with new hosts, the pathogen has a relatively low evolutionary fitness
• needs to be somewhat inefficient so it can pass as much as possible
• influenced by method of transmission

Question 15

Sexually-transmitted pathogens

Answer 15

• will be selected against if they immobilize their host too soon, before the host has the opportunity to find a new sexual partner and unwittingly pass on the pathogen
• ex. Aids have a very long latency period (average of 10 years) with no symptoms

Question 16

Cholera

Answer 16

• caused by eating food or drinking water contaminated with bacterium called Vibrio cholerae
• leads to serve diarrhea, leading to dehydration and possibly death
• has high virulence
• victims often killed fast and then the disease gets passed into new water systems by those cleaning up the mess

Question 17

Cholera outbreak in Haiti (2010)

Answer 17

• first modern large scale outbreak of cholera
• many died
• believed to be in Artibonite River
• Evidence shows that the origin disease was a UN peacekeeper base positioned on a stream that flowed into the river
• Un finally admitted it later

Question 18

Climate change and disease

Answer 18

• climate change is expected to have a substantial effect on the burden of infectious diseases
• humans and animals forced closer together
• rising temps and changing rainfall patterns

Question 19

Avian Malaria

Answer 19

• Hawaiian birds are extremely vulnerable to the disease
• rising temps allowed mosquitos to expand into birds high elevation ranges
• killing a lot of birds
• one way to protect the birds is to kill mosquitos with chemicals. This is hard because mosquitos are very good at surviving. Also the poison that kills the mosquitos kills the other stuff around it

Question 20

Planned extinction

Answer 20

• the future
• use CRISPR to generate mutant gene that leaves female mosquito unable to reproduce, but allows to continue spreading the female infertility to offspring
• could work

Question 21

Ebola

Answer 21

• caused by virus
• symptoms start between 2-21 days after contracting
• people bleed inside and out
• high mortality rate
• virus spreads through direct contact with bodily fluids, such as blood from infected humans or other animals
• big outbreak in 2014-2016 in Africa

Question 22

Ebola and Climate change

Answer 22

• carried by fruit bats in nature, they can carry and be fine
• increase in sudden and extreme weather events is thought to play a role in Ebola outbreaks (bunch of fruit and bats gather allowing disease to pass)
• related to bushmeat consumption
• heat from climate change is making more people need to look to the forest for food.
• deforstation is making the bats come closer to humans
• more and more wild animals are coming into contact with humans

Question 23

Covid-19: natural origin or lab leak?

Answer 23

• ancestral version of the virus must have existed in bats
• we cannot tell from the virus genome if it emerged naturally or via research activities
• actually a decent amount of evidence on both sides
• lack of access to Wuhan lab records leaves many unknowns
• begs the questions should we oversee BSL-4 labs with a global body?

Question 24

BSL-4 labs

Answer 24

• 4 levels with 4 being the most dangers
• store and handle very infectious microbes
• can be privately owned
• no one has much control if people open or no
• should we have inspectors and a governing body?