The ultimate battle: the battle between humans and infectious diseases never stops

The transmissibility of infectious diseases has made them one of the diseases that humans have feared since ancient times. In modern society with developed transportation and global population mobility, infectious diseases can spread all over the world at an alarming speed. In the 1980s, the smallpox virus was eradicated, and humans completely defeated an infectious disease for the first time. But every time a new infectious disease breaks out, humans have to start a new round of challenges. With the continuous advancement of human civilization and technology, how will the relationship between humans and infectious diseases develop in the future world?

Throughout history, every outbreak of infectious diseases has caused a sharp decline in population, economic decline, and even social unrest. Infectious diseases have never stopped tormenting humans. Eradicating infectious diseases has always been the dream of mankind, and we have never given up the fight against infectious diseases. In the battles against plague, cholera, smallpox, syphilis, and tuberculosis, humans have left behind "glorious battles." In addition to chemical agents such as antibiotics, the most successful weapon developed by humans is vaccines.

Vaccines are biological preparations made from bacteria, viruses, tumor cells, etc. that can produce specific immunity in the human body. After vaccination, the immune response produced by the human body is similar to the immune response produced by natural infection. However, vaccines do not cause diseases like viruses and bacteria, so they can safely and effectively prevent infectious diseases.

Although vaccines are effective and safe, they are not completely effective against certain infectious diseases. Why is this? The biggest reason is that the virus strains that cause specific infectious diseases may be variable. For example, some people still get the flu after getting the flu vaccine. This is because the viruses that cause the flu are not only very diverse, but also very cunning. They will continue to mutate during the process of transmission. The flu vaccine is only effective against some special types of viruses, but not against mutated viruses. Therefore, scientific researchers constantly monitor the trend of influenza virus mutations and the types of prevalent strains every year, so as to update the flu vaccine in real time.

In addition, for major diseases such as AIDS, although scientists have been conducting research, no effective vaccine has been able to leave the laboratory. In order for the development speed of vaccines to catch up with the spread of infectious diseases, humans still need to make unremitting efforts.

Image source: Ruijing Vision

The World Health Organization warned in a 2007 report that infectious diseases are spreading faster today than ever before, and that new infectious diseases are more likely to emerge than at any time in history. Since the 1970s, about 40 infectious diseases have been discovered, including SARS, Middle East Respiratory Syndrome, Ebola, avian influenza, influenza A, and most recently, COVID-19. It can be said that not only have the existing infectious diseases not decreased, but many infectious diseases that have never existed before are still emerging. Why is this?

Some of the emergence of emerging and re-emerging diseases is caused by natural processes, such as the evolution of pathogens over time, but many are the result of human behavior and practices. In the 20th century, when the trend of human globalization was formed, the factors that easily cause epidemics of infectious diseases also surged, such as rapid population growth, more frequent and global travel, migration from rural to urban areas, poverty and years of war in some areas, and destructive ecological changes caused by economic development and land use. As the human population increases and enters new geographic areas, the possibility of close contact between humans and animal species that are potential hosts of infectious agents increases, which can lead to animals transmitting pathogens to humans and causing some emerging zoonotic diseases.

Climate change is also increasingly a factor in the spread of infectious diseases. As the Earth's climate warms and habitats change, diseases can spread to new geographic areas. For example, rising temperatures allow mosquitoes to expand their range, allowing some diseases to spread to new areas.

Researchers study viruses under the protection of protective clothing (Photo source: Visual China)

Although humans have made significant progress in the study and treatment of infectious diseases, there are still major challenges in controlling and eradicating these diseases. In order to avoid the losses caused by the COVID-19 pandemic, humans must make efforts in the following aspects in the future: control the spread of emerging infectious diseases, reduce the increase in the incidence and geographical distribution of re-emerging infectious diseases, improve national public health systems, and better communicate on anti-epidemic efforts at the national level.

Vaccine: The ultimate weapon against the epidemic

The word “vaccine” in English comes from the cowpox vaccine used by Edward Jenner, the father of immunology. When humans are vaccinated with cowpox, they can produce antibodies against the smallpox virus. Immunization has saved countless lives and is recognized as the most successful and cost-effective health intervention measure.

Historically, infectious diseases such as hepatitis B, rubella, measles, smallpox, and polio have been effectively controlled through vaccination. Especially for people with weak immunity, such as infants, the elderly, and pregnant women, many vaccines can be called life-saving straws. Vaccines have greatly reduced the outbreak of infectious diseases and have made an extremely important contribution to mankind. At present, humans have successfully eradicated smallpox through vaccines, and the number of infections of most other infectious diseases has also been greatly reduced after effective vaccination. However, due to the limitations of sanitary conditions in various places and the zoonotic nature of most diseases, these infectious diseases have not been successfully eradicated.