COVID-19

A tiny germ can make people sick.

It can spread very fast. This can happen when people breathe near each other. It can also spread if you touch your face with dirty hands.

Some people feel very tired. They might have a cough or a fever. Some people cannot smell or taste food.

Many people do not feel sick at all.

Older people can get very ill. Some people stay sick for a long time. This can last for many months.

Doctors use tests to find the germ. You can even use a test at home.

Washing your hands helps keep you safe.

COVID-19 is a disease caused by a germ called SARS-CoV-2.

This germ is a type of coronavirus. It first appeared in Wuhan, China, in December 2019. The disease spread around the world very quickly. This led to a global pandemic.

People can catch the virus in a few ways. You can breathe in tiny particles in the air. This often happens when people are close together indoors. You can also touch your eyes, nose, or mouth after touching dirty surfaces.

Symptoms can start one to 14 days after you are exposed. Many people feel tired or have a cough. Some people lose their sense of smell or taste. One out of three people show no symptoms at all.

Most people have mild or moderate sickness. However, some people get very ill. Older people face a higher risk of severe sickness. Some people experience long COVID. This means they feel sick for months or years. Doctors use tests to find the virus. You can use rapid tests at home. Health experts also use a more accurate PCR test in a lab.

COVID-19 is a contagious disease caused by a virus called SARS-CoV-2.

This virus belongs to a group known as coronaviruses. It can cause many different health problems in the body. Some people feel very sick, while others feel fine. This disease became a global pandemic when it spread worldwide. The World Health Organization declared a global health emergency in March 2020. They ended that emergency status in May 2023.

The virus works by entering the body through the eyes, nose, or mouth.

You might breathe in tiny particles that stay in the air. This risk is higher when people are close together indoors. You can also catch it by touching surfaces with the virus. Then, you touch your face with unwashed hands. Once inside, the virus uses a spike protein to enter cells. It looks for a specific receptor called ACE2 to attach itself. This receptor is found in high amounts in the lungs.

Scientists first identified the first known case in Wuhan, China.

This happened in December 2019. Most scientists believe the virus came from animals to humans. This process is called zoonosis. It is similar to other outbreaks like SARS-CoV-1 and MERS-CoV. Factors like climate change and wildlife trade may have helped this happen. In February 2020, the World Health Organization gave the virus its official names. They chose COVID-19 to avoid using names of specific places.

Symptoms often start one to 14 days after you meet the virus.

Many people experience fever, cough, or fatigue. Some people lose their sense of smell or taste. About 81% of patients have mild to moderate symptoms. However, 14% develop severe symptoms like trouble breathing. Only 5% develop critical symptoms like respiratory failure. Older people have a higher risk of becoming very ill. Some people also face long COVID for months or years.

We can use many tools to stay safe and healthy.

Doctors use PCR tests in labs to find the virus accurately. You can also use antigen tests at home. Many countries have used mass vaccination campaigns to help. People also use face masks and wash their hands often. Staying apart from others and having good ventilation helps too. Even simple soap can destroy the virus's protective bubble. These steps help keep communities safe from the spread.

COVID-19 is a contagious disease caused by a specific virus known as SARS-CoV-2.

This virus belongs to a large group called coronaviruses. The disease became a global pandemic when it spread across the entire world. In March 2020, the World Health Organization (WHO) declared a global health emergency. This emergency status lasted until May 2023. Understanding this virus is vital because it affects many different systems in the human body.

The virus operates through a specific biological mechanism to infect host cells.

The SARS-CoV-2 particle uses a surface protein called a spike protein (S) to find its target. It looks for a specific receptor called angiotensin-converting enzyme 2, or ACE2. This receptor is most abundant on the surface of type II alveolar cells in the lungs. Once the spike protein connects to the ACE2 receptor, the virus can enter the cell. This process allows the virus to hijack the cell's machinery to replicate itself.

Transmission of the virus occurs through several different pathways.

People can breathe in infectious particles that are suspended in the air. This risk is especially high when people are close together in indoor spaces. Small airborne particles can travel over long distances. Transmission also happens when a person touches their eyes, nose, or mouth after touching contaminated surfaces. People can remain contagious for up to 20 days. Importantly, many people can spread the virus even if they show no symptoms at all.

Symptoms of COVID-19 vary greatly depending on the individual.

Symptoms usually begin between one and 14 days after exposure. Common signs include fever, fatigue, cough, and breathing difficulties. Many people also experience a loss of smell or taste. About 81% of patients develop mild to moderate symptoms, such as mild pneumonia. However, 14% develop severe symptoms like hypoxia, which is low oxygen in the blood. Only 5% of patients develop critical symptoms like respiratory failure or multi-organ dysfunction.

History shows that the first known case was identified in Wuhan, China, in December 2019. Most scientists believe the virus emerged through natural zoonosis. This means the virus jumped from animals to humans. This process is consistent with other outbreaks like SARS-CoV-1 and MERS-CoV. Factors like climate change and wildlife trade may have increased this risk. To prevent social stigma, the WHO issued official names in February 2020. They chose COVID-19 as shorthand for "coronavirus disease 2019."

Beyond the lungs, the virus can cause serious complications in other systems.

Cardiovascular complications can include heart inflammation, arrhythmias, or thrombosis. Some people experience neurological issues like seizures, stroke, or encephalitis. About 20% to 30% of patients show signs of liver injury through elevated liver enzymes. Some patients also suffer from "long COVID." This involves persistent symptoms like fatigue and cognitive issues for months or years. In rare cases, children may develop a serious condition called paediatric multisystem inflammatory syndrome.

Scientists track the virus by studying its many different variants.

These variants are grouped into lineages or clades. The WHO uses Greek letters like Alpha, Delta, and Omicron to name them. This makes it easier for non-scientific audiences to discuss them. Different tools like GISAID and Nextstrain help researchers track these genetic changes. Some variants, like the Omicron variant, have spread to many countries very quickly. Monitoring these changes is essential for developing effective vaccines and treatments.