In this episode of Stuff You Should Know, the hosts take a comprehensive look at the human papillomavirus (HPV), exploring the history of its discovery and its link to cervical cancer. They delve into the different strains, characteristics, and transmission methods of HPV infections.
The blurb sheds light on the prevalence of HPV in the United States, underscoring the role of societal shifts in its widespread transmission. Additionally, it provides insights into the development and effectiveness of the HPV vaccine, addressing the ongoing challenges in vaccine uptake.
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In the 19th and early 20th centuries, scientists linked HPV infections to warts and cervical cancer, as Sanger-Katz reports. German virologist Harald Zirhausen's 1983 discovery of HPV 16 in cervical cancer samples established HPV as a cancer-causing agent, earning him a 2008 Nobel Prize for developing the HPV vaccine.
Over 200 HPV strains exist, classified as either cutaneous (skin) or mucosal (moist areas) types. High-risk mucosal strains like 16 and 18, which hijack cells to multiply uncontrollably, are the main culprits behind HPV-related cancers. HPV 16 causes 90% of HPV-linked oropharyngeal cancers and half of cervical cancers, while HPV 18 causes about 20% of cervical cancers.
The US sees 14 million new HPV infections annually, with 80 million active infections total. Changes in sexual norms since the 1960s, especially increased oral sex, contribute to HPV's prevalence. Importantly, HPV transmits through skin-to-skin contact, not just fluids, making it highly contagious.
Developed in the early 2000s, the HPV vaccine protects against strains 16 and 18. The initial [restricted term] vaccine covered 4 strains; [restricted term] 9 covers 9. The vaccine is highly effective when given before sexual activity begins. However, uptake remains suboptimal, especially for boys, hindering efforts to eliminate HPV-related diseases.
1-Page Summary
The discovery of Human Papillomavirus (HPV) is a hallmark in medical history, with profound implications that led to an effective vaccine and a Nobel Prize.
HPV has the distinction of being the first virus found to cause cancer. In the mid-19th century, scientists intentionally infected their skin with wart extracts, proving that warts were caused by an infection. However, the link to genital warts was initially misunderstood; it wasn't until later that scientific consensus acknowledged genital warts were not a symptom of syphilis or another STI.
In 1917, a German paper established that genital warts could develop independently of STIs by documenting the intentional infection of a virgin girl. Furthermore, the lower incidence of cervical cancer amongst nuns compared to married women led to the hypothesis that cervical cancer might be connected to a sexually transmitted infection.
The critical connection between HPV and cervical cancer came from Harald Zirhausen, who in 1983 discovered papillomavirus, specifically HPV 16, in cervical cancer specimens. This finding established HPV as ...
Background and history of HPV discovery and its connection to cancer
HPV, or human papillomavirus, encompasses over 200 different strains with varying implications for human health. These strains are often classified as either cutaneous or mucosal based on where they typically infect the body.
Cutaneous HPV includes types that primarily infect the skin and lead to common warts, such as those found on the feet and hands. Mucosal HPV, on the other hand, infects moist areas of the body. This variety can result in genital warts and, in more serious cases, cancers in the affected mucosal regions.
Among the many HPV types, a handful, particularly strains 16 and 18, are most notorious for their association with various cancers. HPV 16 is specifically highlighted as a mucosal, high-risk type that has a significant role in causing multiple kinds of cancers. Strain 16 is ancient and human-specific, and it is known to contribute to 90% of HPV-related oropharyngeal cancers, half of all cervical cancers, and a meaningful percentage of other related cancers. HPV 18 is also a high-risk type and is attributed to causing about 20% of cervical cancers.
These high-risk strains are adept at hijacking cells, leading them to multiply uncontrolla ...
Types and characteristics of HPV infections
The prevalence and transmission of human papillomavirus (HPV) are critical public health matters due to the virus's strong affiliation with various cancers and its high rate of infection.
About 14 million Americans contract a new HPV infection each year, and there are at least 80 million Americans currently living with an HPV infection. This high prevalence rate includes more than 37,000 cases of cancer associated with HPV annually, with 22,000 cases in women and 16,000 in men.
Changes in sexual behaviors, particularly regarding oral sex, have contributed to the rise in HPV prevalence. Since the 1960s and 1970s, oral sex has become much more common. This increase in oral sexual activity is now seen as the biggest risk factor for developing oropharyngeal cancer, which HPV can cause. As the number of oral sex partners increases, so does the risk of developing oropharyngeal cancer later in life.
The US Preventative Services Task Force (USPSTF) notes that individuals under 30 are not recommended for HPV testing unless they present notable risk factors. This recommendation is based on the likelihood that a person would ha ...
Prevalence and transmission of HPV
Since its development in the early 2000s, the Human Papillomavirus (HPV) vaccine has made significant strides in preventing infections and associated cancers, with the potential to dramatically reduce or even eliminate certain types of cancer.
The HPV vaccine was a major milestone and became available in 2006, originally intended for girls and women aged 9 to 26. It protected against HPV types 16 and 18—the most common high-risk strains causing cervical cancer—and types 6 and 11, which are associated with genital warts. By 2009, the FDA had licensed the vaccine for use in boys and men within the same age range. Cervical cancer cases and deaths have significantly decreased in the United States since the HPV vaccinations began, as demonstrated by the more than 50 percent decrease in rates from the mid-1970s to the mid-2000s. Early detection and treatment played a crucial role in this decline, with only about 4,000 Americans dying of cervical cancer each year currently.
Initially, two vaccines were available: [restricted term], released by Merck, and Cervarix, from GlaxoSmithKline, with the latter not achieving as much popularity as [restricted term]. In an effort to improve protection, Merck released [restricted term] 9 in 2014, an enhanced vaccine that covers nine different HPV strains.
The vaccine is most effective if administered before individuals become sexually active and does not cure existing HPV infections—it only prevents new ones. A 2021 study found an 87% reduction in cervical cancer among women vaccinated between the ages of 12 and 13. Not only does the vaccine protect against cervical cancer, but it also provides protection for men against genital warts and anal cancer. Studies have shown that the vaccine is quite effective at preventing infections of the four HPV strains it initially targeted.
Furthermore, the vaccine is administered as two shots over a six to twelve-month interval for those under 15, and as three shots over a six-month period for those older than 15. There may still be benefits to receiving the vaccine even if an individual is older than the recommended age range, particularly for those with fewer sexual partners.
Despite the vaccine's effectiveness and benefits, uptake remains suboptimal, especially among boys. This hesitancy limits the vaccine's potential to eradicate HPV-related diseases. The reasons behind the reluctance to ...
The HPV vaccine - development, effectiveness, and impact
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