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Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? for CAT 2025 is part of CAT preparation. The Question and answers have been prepared according to the CAT exam syllabus. Information about Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? covers all topics & solutions for CAT 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer?.

Solutions for Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for CAT. Download more important topics, notes, lectures and mock test series for CAT Exam by signing up for free.

Here you can find the meaning of Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer?, a detailed solution for Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? has been provided alongside types of Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice Directions: Read the passage and answer the following question.Polio – like several other diseases including COVID-19 – is an infection that spreads by stealth. For every case of paralytic or fatal polio, there are 100-200 cases without any symptoms.Germs have a variety of strategies for reproducing and transmitting to new hosts – strategies shaped by the action of natural selection such that only the fittest survive. Some germs, such as smallpox, spread through contact, but they also have another, more powerful way of persisting: theyre durable in the external environment. Smallpox virus particles can remain infectious for years if theyre buried in a scab. Thats one way the virus can keep infecting and spreading: it waits for a new host to happen by. Spreading through water or by insect vectors are strategies, too.But spread by stealth is another strategy and, perhaps, the most terrifying of all. We have been told, for years, to fear pandemics: SARS and MERS (both caused by coronaviruses), Zika, Ebola, the highly pathogenic H5N1 bird flu. But perhaps weve been fearing the wrong thing. Its not just new diseases we have to fear. Its those that spread by stealth.Variola virus, which caused smallpox, one of the deadliest viruses known, had one signal vulnerability: you could see it. Smallpox left its marks on everyone. Some cases were milder than others, but the pox had a tell. It let you know – with a germs equivalent of a roar – where it had been, and that made it easier to eradicate than polio. You knew who was stricken, you learned whom theyd been in contact with, and you vaccinated those people. This technique – ring vaccination – drove smallpox off the Earth. Yet, despite years of relentless work, the World Health Organization has still been unable to eradicate polio.Pathogens that spread by stealth have stalked us through human history. The Black Death of 1346-53 was the greatest pandemic in human history: it burned through the entire known world and killed an estimated 25 million people in Europe alone. But the Black Death behaved very differently from most plague outbreaks today. Plague is a rodent disease, carried, in much of the world, by rats and rat fleas. Its lethal, but its sluggish. The Black Death moved through England at the rate of 2.5 miles a day. No rat-borne disease could possibly have spread that fast.But researchers retrieving bacterial DNA from Black Death victims proved plague did indeed cause the Black Death, leaving scientists with something of a mystery: how did it move so quickly? Finally, Black Death transmission had another, subtler aspect: it was spread by human fleas. Pulex irritans was so common an associate of our medieval ancestors that perhaps they were hardly noticed. The human flea hides in unwashed clothes and bed linens, and it jumps with ease from host to host. Like lung-borne plague, human flea-borne plague is transmitted by stealthy means.The medical community developed antibiotics to treat the plague. But stealth-spreading pathogens through healthy humans might not need to moderate their virulence, not quickly, or, perhaps, not at all. Polio has been with us since the dawn of recorded history, its virulence unmodified over the course of time.Q. Which of the following, if true, would lend most credence to the authors view that Black Death was controlled?a)Once confirmed that Black Death was actually a plague, scientists developed many doses of improved rodenticides.b)Identification of particular rat species liable for the spread of the disease helped medical community to develop effective strategies.c)The invention of cheap soap allowed people to wash themselves and their clothes, and thus set themselves free.d)Large number of casualties in a short period in Europe brought all the major countries around the world together.Correct answer is option 'C'. Can you explain this answer? tests, examples and also practice CAT tests.