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The surprising history of cowpox virus: How did it spread from cows to humans?
Cowpox Virus is an infectious disease caused by the cowpox virus, which mainly manifests as large blisters on the skin, fever and swollen lymph glands. Historically, the disease usually developed after exposure to infected cows, but in recent decades, more cases have come from infected cats. In most cases, the infection occurs on the hands and face and is accompanied by severe pain. Vaccinia virus belongs to the genus Orthopoxvirus and is closely related to variola virus.
Vaccinium is a zoonotic disease that can be spread between humans and animals. The earliest cases occurred in dairy workers who developed the signature pustules on their hands after coming into contact with the teats of infected cows.
Vaccinium is more common in animals such as rats than in cattle. The cowpox virus is similar to the highly contagious and fatal small pox disease, but its symptoms are much milder. It is the similarity between cowpox and smallpox, as well as the immunity of dairy workers to smallpox, that inspired the development of the modern smallpox vaccine. The creation and administration of this vaccine is attributed to British doctor Edward Jenner.
Jenner first described cowpox in 1798 and proposed the concept of "vaccination", which is derived from the Latin "vaccinus", meaning "from cows". Once vaccinated, the recipient will develop antibodies to cowpox and will also be immune to the smallpox virus. The successful application of this type of cowpox vaccine led to the World Health Organization in 1980 declaring smallpox the first disease in the world to be eradicated by vaccination efforts.
Applications of cowpox in medical treatment
While cases of cowpox are uncommon in nature, studies have found that the vaccine can replicate and spread from person to person. Jenner's initial vaccine used lymph fluid from a cowpox pustule of a dairymaid, and later developed an "arm-to-arm" vaccination method. However, this artificial liquid delivery introduced many complications, so Italy first came up with a safer way to make the vaccine.
The Swedish cowpox vaccine production process is called "reverse vaccination". This method first injects the humanized cowpox virus into young cows and then transfers them from the calf to other calves, thereby safely and effectively mass-producing the vaccine.
This production method brought real profits, and the entrepreneurs only needed the lymph fluid of calves and infected cows to create a crude version of the vaccine. W.F. Elgin of the U.S. National Vaccine Agency proposed a slightly streamlined technology, which was demonstrated at meetings of the U.S. provincial health committees.
The development and history of vaccines
Between 1770 and 1790, at least six people attempted to use the cowpox vaccine to immunize humans against smallpox. Among them, British farmer Benjamin Jesty successfully vaccinated his family against cowpox in 1774. After vaccination, his family became immune to the small pox. This case attracted widespread attention, especially in 1796, when Jenner successfully used cowpox to protect an eight-year-old boy who had never been infected with smallpox.
Jenner's research popularized the concept of vaccination and made it common among the population. Although Jesty is credited with being the first to use cowpox for vaccination, it was Jenner who popularized and gained recognition for the concept.
Eventually, the cowpox vaccine became the main preventive measure against small pox, and as vaccination became more widespread, more and more people gradually embraced the change.
Contemporary and future prospects
Today, vaccinia virus is mainly found in Europe, especially the United Kingdom, and human cases are very rare. Most infections are usually transmitted from household pets. Although symptoms of human infection are usually limited to pustules at the site of contact, the infection can be fatal in patients with compromised immune systems.
The success of the cowpox vaccine reflects the great potential of vaccinology, yet in the contemporary era, other orthopoxviruses such as monkeypox virus are still circulating in some communities and continue to infect humans. This forces us to think: as the virus continues to mutate and evolve, can our immune system continue to cope with these challenges?
