https://www.quora.com/Is-HPV-a-reasonable-candidate-for-disease-eradication
Is HPV a reasonable candidate for disease eradication?
4 Answers
Probably not. There are a few things that make a disease a good candidate for eradication, and HPV doesn't quite fit the bill.
What makes a disease a good candidate?
1. The disease is highly visible. Small pox, for example, was a pretty tough disease to hide. The signature rash appeared all over the body in a spiral pattern, starting with the extremities and working their way around. You can see in the image below that the rash concentrated in some of the most visible places: the head, hands and feet. You couldn't miss it.
Image from: CDC Smallpox | Smallpox Overview
2. The symptoms are unique. Many diseases look alike. It's much harder to beat a disease if it's not easily identified. The rash for small pox was characteristic. For the most part, people knew what it was and -- most importantly -- what to look for.
3. There is a short incubation period. This is the period of time between the moment a person is infected and the onset of symptoms. Measles, for example, is highly visible and has a characteristic rash, but it has a fairly long incubation period (10-12 days), and a person can become contagious before the symptoms are apparent. The shorter the incubation period, the faster cases can be identified and contained.
4. It is transmitted human-to-human. That is, there isn't something that carries the pathogen (the thing that causes disease) from person to person -- or a "vector" -- and no other animal can serve as a host. Yellow fever, for example, can live in both humans and monkeys, and is spread by mosquitoes. So if we did end up successfully eliminating yellow fever in humans, it's possible it could reemerge via the monkey-mosquito route if we let our immunity wane.
Image from: A List of Some Vector Diseases
5. There is an effective method of preventing transmission. More often than not, this refers to an effective vaccine that provides lifelong immunity. With smallpox, one shot could protect most people for the rest of their lives.
6. It is stable. This means that it doesn't change easily. Viruses, especially, are prone to antigenic drift (changing little by little over time) or antigenic shift (changing in a big way very quickly). If the pathogen continues to morph, you're aiming at a moving target.
Image from: Rule of 6ix: November 2011
Some other factors to consider for a good eradication candidate:
7. There are sufficient resources. Eradication has a HUGE return on investment, but the investment is pretty substantial. Significant resources need to be poured into eradication programs for them to work. Billions of dollars have been spent on the polio eradication campaign, and now the disease is only in three countries. But if resources were to be scaled back, polio could easily spread across the globe again. Concentrating those resources is critical.
8. There is enough political will. The world is increasingly interconnected. People can literally fly around the world in a single day. It takes massive coordination from the world's governing powers to make sure that everyone works in tandem.
So ... how does HPV measure up against these characteristics?
Highly visible? | No. Most people with HPV don't even know they are infected and show no symptoms.
Unique symptoms? | Yes and no. As I mentioned, most HPV infections result in no symptoms. Some strains of HPV can cause genital warts, however, and these are pretty characteristic. I'll spare you a graphic picture, but they are likened to cauliflower.
Short incubation period? | No. The incubation period varies widely, depending on the HPV sub type, but all estimates are long, typically ranging from one month to years.
Human-to-human transmission? | Yes. Humans are the only known, natural hosts of HPV.
Effective prevention method? | Yes and no. We have safe and effective vaccines; however, the vaccines can only protect against 2, 4 or 9 HPV sub types (depending on the vaccine brand). All of these vaccines prevent the two types of HPV responsible for the vast majority of HPV-related cancers, and two of the vaccines prevent the two sub types responsible for nearly all genital warts. But there are more than 100 different sub types of HPV, and roughly 40 that affect the genital area. We have no practical way to prevent the other subtypes. Even condoms don't fully protect against HPV.
Is it stable? | Fairly so, yes. HPV is a double-stranded DNA virus, so it doesn't change as much as an RNA virus might.
Sufficient resources? | Probably not. To start, HPV is REALLY, REALLY common. Nearly all sexually active adults become infected with HPV at some point in their lifetime -- in large part, because many people don't even know they are infected and so continue to spread it. What's more the vaccine requires three doses, months apart, to provide full protection. Tackling HPV would require massive, and I mean massive amounts of money and manpower.
Political will? | Unlikely. People don't like talking about sexually transmitted infections, least of all politicians. Eradicating the four sub types included in the HPV4 vaccine would take nearly universal vaccination in every country on the planet, and there would still be 96+ sub types left circulating.
Perhaps if we were able to develop a universal HPV vaccine that protected against every sub type for life, eradication would be feasible. But given the technology and biological considerations that we have today, HPV is just not a reasonable candidate for eradication.
Sources:
Disease Eradication
Page on Cdc about Measles
The Principles of Disease Elimination and Eradication
Page on Polioeradication
Page on Cdc about HPV
Viruses and Evolution
EDIT: The answer was modified to acknowledge a new vaccine that protects against 9 strains of HPV.
What makes a disease a good candidate?
1. The disease is highly visible. Small pox, for example, was a pretty tough disease to hide. The signature rash appeared all over the body in a spiral pattern, starting with the extremities and working their way around. You can see in the image below that the rash concentrated in some of the most visible places: the head, hands and feet. You couldn't miss it.
2. The symptoms are unique. Many diseases look alike. It's much harder to beat a disease if it's not easily identified. The rash for small pox was characteristic. For the most part, people knew what it was and -- most importantly -- what to look for.
3. There is a short incubation period. This is the period of time between the moment a person is infected and the onset of symptoms. Measles, for example, is highly visible and has a characteristic rash, but it has a fairly long incubation period (10-12 days), and a person can become contagious before the symptoms are apparent. The shorter the incubation period, the faster cases can be identified and contained.
4. It is transmitted human-to-human. That is, there isn't something that carries the pathogen (the thing that causes disease) from person to person -- or a "vector" -- and no other animal can serve as a host. Yellow fever, for example, can live in both humans and monkeys, and is spread by mosquitoes. So if we did end up successfully eliminating yellow fever in humans, it's possible it could reemerge via the monkey-mosquito route if we let our immunity wane.
5. There is an effective method of preventing transmission. More often than not, this refers to an effective vaccine that provides lifelong immunity. With smallpox, one shot could protect most people for the rest of their lives.
6. It is stable. This means that it doesn't change easily. Viruses, especially, are prone to antigenic drift (changing little by little over time) or antigenic shift (changing in a big way very quickly). If the pathogen continues to morph, you're aiming at a moving target.
Some other factors to consider for a good eradication candidate:
7. There are sufficient resources. Eradication has a HUGE return on investment, but the investment is pretty substantial. Significant resources need to be poured into eradication programs for them to work. Billions of dollars have been spent on the polio eradication campaign, and now the disease is only in three countries. But if resources were to be scaled back, polio could easily spread across the globe again. Concentrating those resources is critical.
8. There is enough political will. The world is increasingly interconnected. People can literally fly around the world in a single day. It takes massive coordination from the world's governing powers to make sure that everyone works in tandem.
So ... how does HPV measure up against these characteristics?
Highly visible? | No. Most people with HPV don't even know they are infected and show no symptoms.
Unique symptoms? | Yes and no. As I mentioned, most HPV infections result in no symptoms. Some strains of HPV can cause genital warts, however, and these are pretty characteristic. I'll spare you a graphic picture, but they are likened to cauliflower.
Short incubation period? | No. The incubation period varies widely, depending on the HPV sub type, but all estimates are long, typically ranging from one month to years.
Human-to-human transmission? | Yes. Humans are the only known, natural hosts of HPV.
Effective prevention method? | Yes and no. We have safe and effective vaccines; however, the vaccines can only protect against 2, 4 or 9 HPV sub types (depending on the vaccine brand). All of these vaccines prevent the two types of HPV responsible for the vast majority of HPV-related cancers, and two of the vaccines prevent the two sub types responsible for nearly all genital warts. But there are more than 100 different sub types of HPV, and roughly 40 that affect the genital area. We have no practical way to prevent the other subtypes. Even condoms don't fully protect against HPV.
Is it stable? | Fairly so, yes. HPV is a double-stranded DNA virus, so it doesn't change as much as an RNA virus might.
Sufficient resources? | Probably not. To start, HPV is REALLY, REALLY common. Nearly all sexually active adults become infected with HPV at some point in their lifetime -- in large part, because many people don't even know they are infected and so continue to spread it. What's more the vaccine requires three doses, months apart, to provide full protection. Tackling HPV would require massive, and I mean massive amounts of money and manpower.
Political will? | Unlikely. People don't like talking about sexually transmitted infections, least of all politicians. Eradicating the four sub types included in the HPV4 vaccine would take nearly universal vaccination in every country on the planet, and there would still be 96+ sub types left circulating.
Perhaps if we were able to develop a universal HPV vaccine that protected against every sub type for life, eradication would be feasible. But given the technology and biological considerations that we have today, HPV is just not a reasonable candidate for eradication.
Sources:
Disease Eradication
Page on Cdc about Measles
The Principles of Disease Elimination and Eradication
Page on Polioeradication
Page on Cdc about HPV
Viruses and Evolution
EDIT: The answer was modified to acknowledge a new vaccine that protects against 9 strains of HPV.
'infection eradication' 카테고리의 다른 글
| 예방접종 지침 (0) | 2016.12.29 |
|---|---|
| 국방부 (0) | 2016.12.28 |
| [스크랩] [복지부, 결핵예방법 시행령·시행규칙 개정] 결핵 공포..끝나지 않았다 (0) | 2016.12.27 |
| [스크랩] `철새 고속도로` 올라탄 AI, `바이러스 행성` 되는 지구 (0) | 2016.12.26 |
| 콜레라 (0) | 2016.11.28 |