What do the "A, B, and C" categories of infectious diseases represent? Does that mean we don't have to worry about COVID-19 if it's not a category A?

"People died like sheep. The sick wandered naked in the streets, looking for water until they fell down and died. Dogs, crows and eagles also died from the disease after eating the corpses of people lying everywhere. Those who survived had lost their fingers, toes, eyes or their memories." One day in 430 BC, the Greek historian Thucydides recorded the plague that swept across Athens.

"The Plague of Athens" by painter Michelle Thwaites, image source: Wikimedia

There are many records of plagues (or more precisely, infectious diseases) in history. In addition to the Athenian Plague just mentioned, famous events include the Antonine Plague, which was a collective outbreak of multiple plagues, the Justinian Plague, the world's first large-scale plague outbreak, the Black Death in Europe, which raged for 300 years and killed nearly 200 million people, the smallpox epidemic that broke out in the Americas at the end of the 15th century, the American yellow fever epidemic that raged for nearly two centuries, the cholera that caused seven world pandemics, the Spanish flu, which was called the nightmare of mankind in the 20th century, the typhus that killed nearly 3 million people during the First World War, and the malaria epidemic that is still rampant, with 300 million cases occurring each year.

It can be seen from this that infectious diseases have always posed a huge threat to us, and the threat has never stopped and will not disappear .

01

What are infectious diseases?

Are they all deadly?

Infectious Diseases (English name: Infectious Diseases) are a type of disease caused by various pathogens that can be transmitted between people, animals, or between people and animals . Different from common diseases, infectious diseases have very clear pathogenic factors, which are pathogens. Most pathogens are microorganisms (including viruses, bacteria, and fungi), and a small number are parasites. In other words, they are all active and can reproduce. Dead or inactivated pathogens generally do not induce disease .

Copyright image, no permission to reprint

Another very important difference between infectious diseases and common diseases is contagiousness. For example, if someone has high blood pressure, the people around him will not develop high blood pressure just because of contact with him, living or working with him. Even if someone happens to be sick, they are relatively independent and there is no causal relationship.

However, infectious diseases are different.

People suffering from a certain infectious disease are usually called infected people. The pathogens in their bodies will not only cause the infected people to become ill or be in a carrier state, but will also cause people around them who lack effective protection to be infected through direct contact with others, respiratory droplets, body fluids, fecal-oral and other means .

Copyright image, no permission to reprint

Take the COVID-19 infection as an example. The infected person will expel droplets containing the COVID-19 through breathing, talking, coughing and sneezing. When other people come into close contact without protection, they will be infected with a high probability. After an incubation period, the newly infected person will be contagious again, and then transmit the pathogen to more susceptible people. This is contagiousness.

Of course, different types of infectious diseases have different infectivity, transmission routes, susceptible populations, and impacts on the human body . For example, chickenpox is an infectious disease caused by the varicella-zoster virus, which is more common in children aged 2-6 years old. It is mainly transmitted through droplets through the respiratory tract or contact infection. It is highly contagious, but the impact on health is relatively small, and it can be immunized through vaccination. However, some infectious diseases have a huge impact on us, such as the plague mentioned above. It is a highly contagious disease caused by Yersinia pestis transmitted through rat fleas. If it is not treated, the mortality rate can be as high as 30%-60%.

02

infectious disease

How to classify and manage?

Countries will take corresponding management and control measures based on the severity of the impact of infectious diseases. Infectious diseases that are required to be strengthened in the form of law are called statutory infectious diseases. Only those infectious diseases with high incidence, wide prevalence and serious harm will be included.

China has specially formulated the "Law of the People's Republic of China on the Prevention and Control of Infectious Diseases". Currently, there are 40 legal infectious diseases in China, including 2 Class A infectious diseases, 27 Class B infectious diseases, and 11 Class C infectious diseases. Different levels mean different degrees of severity, and different levels of supervision, monitoring and management measures will be taken .

Copyright image, no permission to reprint

Take Class A infectious diseases as an example, including plague and cholera. They have a huge impact on human health and social security and are highly contagious diseases . Therefore, management must also be very strict. According to current regulations, once discovered, it must be reported within 2 hours in order to quickly conduct epidemiological investigations, control the source of infection, cut off the transmission route, and prevent the continuation of the epidemic.

Category B infectious diseases are those that require strict management , including 27 types such as novel coronavirus infection, infectious atypical pneumonia, highly pathogenic avian influenza, viral hepatitis, etc. Such infectious diseases must be prevented and controlled in strict accordance with relevant regulations and prevention and control plans, and must be reported within 24 hours once discovered.

Of course, there are exceptions. For example, although pulmonary anthrax and infectious atypical pneumonia belong to Category B, they must be reported within 2 hours after discovery. Category C infectious diseases are also called monitored infectious diseases , including 11 types such as schistosomiasis, leprosy, and influenza, which must also be reported within 24 hours after discovery.

03

What does “Class B Class A pipe” mean?

When a new infectious disease emerges, due to the lack of understanding of its etiology and epidemiological characteristics, its infectivity, pathogenicity and pathogen mutation characteristics are still unclear. In order to protect people's lives and health to the greatest extent, China has responded to new infectious diseases such as SARS in 2003, highly pathogenic avian influenza in 2005, and influenza A (H1N1) in 2009. The effective experience has been to classify them as Class B infectious diseases as soon as possible, but implement Class A infectious disease control measures .

However, with the deepening of research and understanding of the epidemic patterns of diseases and pathogens, the development and application of clinical treatment methods, vaccines and drugs, and the accumulation of effective prevention and control measures, SARS and avian influenza, which were once subject to "Class B A management", have returned to Class B infectious disease control measures, while influenza A (H1N1) has been incorporated into influenza and monitored and managed as Class C infectious diseases. This is the origin of Class B A management. Recently, after a comprehensive assessment of factors such as virus mutation, epidemic situation and my country's prevention and control foundation, my country's new crown epidemic prevention and control policy has undergone major adjustments. From January 8, 2023, "Class B B management" will be implemented for new coronavirus infection.

This work is specifically announced and implemented by the health administrative department of the State Council after timely reporting to the State Council for approval. The people's governments of provinces, autonomous regions, and municipalities directly under the Central Government may, based on the circumstances, decide to manage and announce the common and frequent local infectious diseases in their administrative regions as Class B or Class C infectious diseases and report them to the health administrative department of the State Council for record.

04

Not a Category A infectious disease

Can we relax our vigilance now?

Of course not. The reason why infectious diseases need to be monitored and managed is because of their infectiousness and harmfulness. Even if some infectious diseases are managed as Class B and Class C, it does not mean that we can relax our daily protection , because once infected, they can still cause a wide range of impacts.

For example, norovirus infection is managed as other infectious diarrheal diseases in Class C infectious diseases, but it causes a large-scale impact almost every year around the world. The World Health Organization estimates that hundreds of thousands of people die from norovirus infection each year. Since 2013, most outbreaks of other infectious diarrheal diseases in China have been mainly caused by norovirus. Everyone is susceptible, it can occur throughout the year, and there is no vaccine to prevent infection. The most direct and effective way is to pay attention to frequent hand washing and food hygiene.

Copyright image, no permission to reprint

Therefore, prevention is still an important means to reduce the occurrence of infectious diseases in daily life. On the one hand, we should pay attention to the epidemic information of infectious diseases released by the health department, increase relevant knowledge reserves, and take corresponding protective measures such as vaccination, frequent hand washing, and wearing masks . On the other hand, we should pay attention to a reasonable diet, adequate sleep, and moderate exercise to enhance our own immunity and reduce the chance of infection. If infection occurs, don't worry too much, actively seek treatment and avoid infecting others.

Author: Zhang Yu, researcher at Chinese Center for Disease Control and Prevention

Review | Tang Qin, Deputy Secretary-General and Researcher of the Science Popularization Expert Committee of the Chinese Medical Association

If you have questions about the coronavirus

Especially those who hope to get analysis and answers to rumors and rumors related to the epidemic

Please leave us a message

The cover image and some images in this article are from the copyright library

Reproduction of image content is not authorized