Patient zero is generally taken to mean the first case in a disease outbreak – but the term is often applied in different ways. When it comes to zoonotic diseases (ones that jump from animals to humans, like SARS-CoV-2), patient zero might refer to the first-ever human case – the point at which the virus spills over from an animal to a human. For the general public, however, patient zero is often used to refer to the first case in a particular region, or the first case that's come to the attention of health authorities. However, these are not always the same thing. Sometimes the first case that's notified to us is not the first case in an outbreak. Similarly, just because someone is identified as the first case doesn't mean they spread the disease to anyone else, or behaved irresponsibly – with something like coronavirus, they may not even know they're sick.

This is part of the reason why patient zero is not a term epidemiologists or public health experts tend to use - it's not specific enough. They prefer the term index case to refer to the first person officials became aware of in an outbreak (which gives them a clue something's going on), and primary case to refer to the person who introduces a disease into a new population - a community, country or the world. Sometimes, the primary case and the index case will be the same person, but not always. For many outbreaks - such as HIV/AIDS, and possibly COVID-19 – we will never know the primary case.

While the use of the term patient zero can be fraught, tracing outbreaks back to their beginnings remains important in public health. In the early days of an outbreak, it's still possible to catch embers of disease before they become full-blown fires. "You can actually stamp them out, by identifying every case, tracking every contact, quarantining them, making sure there's no further spread," Professor Raina Macintyre, head of biosecurity at UNSW's Kirby Institute says. But even after those critical first days or weeks, tracing cases back to patient zero can still give both health experts and relevant authorities for insights into how disease spreads and understands the role that health services and adequate sanitation systems play in controlling the spread of the disease. That's the purpose of trying to understand an index case or a first case – to establish the opportunity to learn from the breakout and try to make sure it doesn't happen again.

According to the passage which statement is true about SARS-CoV-2?

According to sociologists, there are several different ways in which a person may become recognized as the leader of a social group in the United States. In the family, traditional cultural patterns confer leadership on one or both of the parents. In other cases, such as friendship groups, one or more persons may gradually emerge as leaders, although there is no formal process of selection. In larger groups, leaders are usually chosen formally through election or recruitment.

Although leaders are often thought to be people with unusual personal ability, decades of research have failed to produce consistent evidence that there is any ca gory of “natural leaders”. It seems that there is no set of personal qualities that all leaders have in common; rather, virtually any person may be recognized as a leader if the person has qualities that meet the needs of that particular group.

Furthermore, although it is commonly supposed that social groups have a single leader, research suggests that there are typically two different leadership roles that are held by different individuals. Instrumental leadership is leadership that emphasizes the completion of tasks by a social group. Group members look to instrumental leaders to “get things” done. Expressive leadership, on the other hand, is leadership that emphasizes the collectivewell-being of a social group’s member. Expressive leaders are less concerned with the overall goals of the group than with providing emotional support to group members and attempting to minimize tension and conflict among them. Group members expect expressive leaders to maintain stable relationships within the group and provide support to individual members.

Instrumental leaders are likely to have a rather secondary relationshipto other group members. They give orders and may discipline group members who inhibit attainment of the group’s goals. Expressive leaders cultivate a more personal or primary relationship to others in the group. They offer sympathy when someone experiences difficulties or is subjected to discipline, are quick to lighten a serious moment with humor, and try to resolve issues that threaten to divide the group.

As the differences in these two roles suggest, expressive leaders generally receive more personal affection from group members; instrumental leaders, if they are successful in promoting group goals, may enjoy a more distant respect.

What does the passage mainly discuss?

What is the passage mainly about?

The five senses of the body include sight, hearing, taste, smell, and touch. Human beings and most other animals use the five senses to help them live and experience the world around them. The senses also help people to learn, protect themselves, and to enjoy the differences between foods, sounds, and other experiences a person has in life. The senses also work together to give you a clear picture of the activities around you.

The first sense is sight, which depends on the eyes. People use their eyes to see the people, objects, and other items around them. Of course, the sense of sight is also helpful for reading, traveling, driving, and moving from place to place each day. Inside the eye there are special lenses that take in light to help people see things. If it is too dark, a person will have trouble seeing. The eyes can also adjust to the amount of light available. Many people, though, young and old, may also need glasses to help them see clearly. Some people may be able to see things up close, but not far away, which means they are nearsighted. If a person can see far away but not up close, they are farsighted. If a person is blind, there are special books written in braille which helps them feel the raised letters. Some blind people also have special dogs to help guide them from place to place in their home and when they go places.

The second sense, hearing, depends on the ears. There are actually three parts of the ear, the outer ear, middle ear, and the inner ear. The outer ear is the part other people can see. The outer ear catches the sound waves as they travel to the person and then sends them into the ear. The outer ear acts like a funnel collecting the different sounds a person experiences. The middle ear contains the eardrum and several bones which transfers sound from the outer ear to the inner ear. The inner ear consists of tubes and passages that takes the sound vibrations and sends themto your brain for understanding. [A]

The third sense, smell, depends on your nose. Inside the nose there is a substance that takes the fumes of an odor and then sends it to the brain. If a person gets a cold the sense of smell may not be as strong. The nose also helps clean the air a person breathes by filteringit. Inside the nose there are tiny hairs, called cilia, which act as cleaners to help keep substances in the air from entering a person's body through the nose. In addition, the nose affects the way a person speaks. If a person holds their nose while speaking, their voice will sound different. Smell also helps with the sense of taste. As a person tastes the food in their mouth, the aroma of the food enters a person's nose. [B]

The next sense, feeling, or touch, can be experienced throughout the entire body through a person's skin. Some parts of the body are more sensitive to touch than other parts. The skin has parts in it that collect information and sends it the brain. Most of a person's feeling is done by the hands. In addition, when a person has a stomach ache or feel other kinds of pain, the sense of touch is working from inside the body. [C]

The final sense, taste, comes from the taste buds on a person's tongue. As stated earlier, the sense of smell also affects the sense of taste. The tongue tastes four different flavors: salty, sweet, sour, and bitter. Many foods a person eats may be a combination of the four main flavors. The tongue can also feel whether something in a person's mouth is hot, cold, creamy, crunchy, or dry.

In summary, the five senses are sight, hearing, smell, feeling, and taste. [D]

Which of the following senses is most helpful for reading, traveling, and moving from place to place?

A “secondary relationship” mentioned in the last paragraph between a leader and the members of a group could be best characterized as.

The Human Heart

The human heart is an amazing organ of the human body. The heart is an organ which pumps life-giving blood throughout the body. It works together with blood and blood vessels to supply all of the needs of the cells.

The heart is located in the middle of the chest and slightly to the left. It is divided into two halves and has two hollow spaces or chambers. The blood enters the atria, which is the upper chamber and is then pumped to the ventricles, two lower chambers. Blood from the ventricles goes to the lungs and to every cell in the body. [A]

An artery is a blood vessel which carries blood away from the heart. A main artery may be as thick as a thumb. Blood is made up of red cells, white cells and platelets floating in a fluid called plasma. Plasma is a liquid and can easily pass through small blood vessels into cells and makes up over one-half of the blood. The plasma carries nutrients (food) from the stomach to be used as fuel for energy. Plasma also helps keep the body warm.

The blood then returns to the heart through blood vessels called veins. The veins on the skin, may look blue, especially on the hands and arms. The walls of a vein are much thinner than those of an artery. Two large veins bring the blood back to the heart. One comes from the brain and the chest. The other comes from the stomach and lower body. [B]

Blood doesn't flow at the same speed through all of the body. As it gets farther away from the heart, it slows down. It goes slowly when the red blood cells carrying the food and oxygen squeezethrough into the cells. [C]

The heart beats or pumps every second of the day or night. It beats or pumps 100,000 times a day, every day of a person's life. Every time a heart beats or pumps out a stream of blood, this beat, called a pulse, can be felt on the inside of the wrist. The pulse rate in an adult is between sixty and one hundred beats per minute. Children's pulse rates range from ninety to one hundred twenty beats per minute. [D]

In summary, the circulatory system which includes the heart, blood vessels and blood, work together to supply the cells with all the food and oxygen a body needs to maintain life. Blood is made up of red cells, white cells and platelets floating in a fluid called plasma. Arteries carry blood away from the heart, and veins carry the blood back to the heart. The heart beats thousands of times a day, every day. It beats much faster in children. The human heart is an amazing organ which is part of a system of many veins, arteries, and vessels which moves blood throughout the body keeping humans alive.

What is the main purpose of the heart?

Bones support the human body. They are the structure on which the skin hangs. Without bones the body would collapse. A person could not walk or run. Bones provide both support and protection for parts of the body.

In the front of the body the bony rib cage covers the chest. Underneath are the heart and lungs. The ribs are bones which protect the heart, lungs and stomach in case of injury. The skull protects the brain. The bones in the back (or spine) protect the nerves of the spinal column. [A]

The bones store minerals needed by other parts of the body. When the minerals are needed, they will be released into the blood. They also form new red and white blood cells each day. New bone is still made until a person reaches the age of thirty-five. When a person gets much older, the bones start to weaken. The minerals begin to disappear from the bones.

Besides storing minerals and forming blood cells, the bones work with muscles and joints. They allow movement in the body. The place where two bones come together is called a joint. The knee joint is the biggest and strongest joint in the body. Ligaments link bones together at the joints. They are very strong and can stretch. Muscles are attached to bones by tendons. The muscles and tendons together allow the bones move. [B]

The whole bone structure of the body is called the skeleton. The skull protects the brain, eyes, face, jaw and ears. Vertebrae make up the column of bones running down the back. Between each vertebra is a small cushion called a disk. The vertebrae are hollow. Nerves run down through the hollow parts to the whole body.

Knees, hands, feet and legs all have different kinds of bones. Some of these bones can move freely. Some are bound tightly together. Arm bones are connected at the top to the collarbone and shoulder bone. They are connected at the bottom to the hand. Leg bones are attached to the spine at the top by the group of bones called the pelvis. The upper part of the leg is the thigh bone. Itforms part of the knee. The lower part of the leg is made up of two bones. They are attached to the foot at the bottom. [C]

Bones are actually living cells. The bones grow and change over time. A person is born with three hundred bones. Some of these bones can join together. By the time a person becomes an adult, he will have only about two hundred and six bones.

In summary, bones are a necessary part of the body. They provide protection and support for the vital organs, like the heart, brain and lungs. The bones are strong and can handle heavy weights. They allow a person to walk. They work with muscles to help the body move and stretch. [D]

Which of the following bones protect the heart?

According to the passage, which antioxidant is especially good for people who do a lot of physically demanding activities?