This new study, published in the journal JAMA Oncology, is the first to show conclusively that HPV-16's presence in the mouth leads to the development of oropharyngeal cancer.
This follows a study in The New England Journal of Medicine which showed that those infected with HPV were 32 times more likely to develop oral or throat cancers.
And previous research published in the Journal of Clinical Oncology found HPV now accounts for more head and neck cancers than tobacco or alcohol.
Spread by skin-to-skin contact, not just by sex, HPV affects almost everyone at some stage in their life.
In most people, the immune system fights it off and it does no harm.
But on rare occasions, the virus takes hold, leading to a chain of events that ends in cancer of the cervix, penis, anus, vagina or mouth.
Around 15 strains can cause cervical cancer - and HPV-16 is the most common.
The most dangerous HPV's, 16 and 18, which are transmitted through sexual contact are known to cause up to 95 per cent of cervical cancers.
Now these two HPV's are also being linked to oral cancer.
A different study done by Dr No-Hee Park, a leading expert in head and neck cancers at UCLA, showed that the mouth was, at the cellular level, structurally very similar to the vagina and cervix.
Both organs have the same type of epithelial cells that are the target of HPV 16 and HPV 18.
The majority of oral cancers are cancers of epithelial cells, primarily squamous cell carcinomas, not unlike the cancers that affect the cervix.
Dr Park's study also showed that smoking and drinking alcohol help promote HPV invasion.
Combine tobacco and alcohol with HPV, and the epithelial cells in the mouth, and you may have the formula for the development of an oral cancer.
The new research, carried out at Albert Einstein College of Medicine in New York, suggested people carrying the virus in their mouth were an alarming 22 times more likely to develop a potentially lethal tumour.
The finding was based on almost 97,000 people who provided mouthwash samples and were cancer-free at the beginning of the project.
They were followed for an average of four years, during which time a total of 132 cases of head and neck cancer were identified.
The study participants were compared with 396 healthy people who acted as controls.
Mouthwash samples were analysed for the presence of several types of oral HPVs in both groups.
These revealed people with HPV-16 in their mouthwash were 22 times more likely to develop oropharyngeal cancer (oropharynx is the part of the throat directly behind the mouth) than were those with no detectable trace of the virus HPV-16 in their samples.
In addition, the researchers found for the first time that the presence of other types of oral HPVs, known as beta and gamma, which are usually detected in the skin, were also associated with the development of head and neck cancers.
This indicated a broader role for HPVs in causing these cancers than has been recognised to date.
Dr Ilir Agalliu, of the Albert Einstein College of Medicine, New York, said: 'This study shows using easily collected oral mouthwash samples may help in predicting people's risk for developing head and neck cancers.'
Cases of oral cancer have increased over the past 30 years.
Oropharyngeal cancer is the type that affected actor Michael Douglas.
In a June 2013, the Fatal Attraction star seemed to indicate his disease was brought on by human papillomavirus (HPV), contracted through cunnilingus.
His rep later denied that he was pinpointing the cause of his own cancer and merely stating one of the many causes of oral cancer, which include smoking and drinking.
However he beat the odds by recovering from a tumour categorised as stage 4, which often is terminal.
Commenting on the new study, Dr Nigel Carter, chief executive of the British Dental Health Foundation, said: 'HPV-related cancers have rapidly increased over the last few years.
'Early detection of mouth cancer dramatically improves the chances of survival from 50 to 90 per cent - so it's extremely important to be on the lookout for any signs and symptoms which could be related to the disease.'
He added: 'Be alert to mouth ulcers which do not heal within three weeks, red or white patches in the mouth and any unusual swellings or lumps in the head or neck area, and if you spot anything unusual to get examined straight away.
'Your dentist will check for signs of mouth cancer during your regular check-up so it is important that you visit your dentist regularly to catch any signs which you may miss yourself.'
Dr Jana Witt, Cancer Research UK's health information officer, said the work added to a growing body of evidence but said it was important to stress the risk was low.
'It's already established that the human papillomavirus (HPV) is linked to some types of mouth and throat cancer and this research adds an important part to that evidence - showing that having an HPV infection leads to a higher risk of developing one of these cancers later on in life,' she said.
'But the study wasn't able to give a very accurate estimate for how much the risk of oropharyngeal cancer, which affects part of the throat, was increased and it's far from certain that the risk would be 22 times higher.
'Previous research has shown that oral sex can raise the risk of mouth and throat cancers because it can spread HPV, but it's important to remember that the chance of developing cancer if you have oral sex is still low.
'Not smoking, cutting down on alcohol and getting plenty of fruit and veg are all good ways to cut the risk of these cancers.'
WHAT IS THE HUMAN PAPILLOMA VIRUS?
What is HPV?
The human papilloma virus is the name given to a group of viruses that affect a person's skin as well as the membranes lining the body - for example, in the cervix, anus, mouth and throat.
HPV is very common and highly contagious.
More than three quarters of sexually active women acquiring it at some point in their lives.
And in the U.S. it is the most common sexually-transmitted infection.
Most people are oblivious to the fact they have been infected and as a result can pass it on to a partner without realising.
There are more than 100 types of HPV - around 40 of which affect the genital area.
What does HPV infection do?
The majority (nine in 10) of infections disappear of their own accord within two years.
But the other 10 per cent of infections can cause health problems, including:
- genital warts
- cervical cancer
- a type of head and neck cancer, oropharyngeal cancer, in the back of the throat including at the base of the tongue and tonsils in men and women
- anal cancer
- vulva and vaginal cancer
- penile cancer
The types of HPV that cause genital warts are different to those infections that cause cancer.
Other HPV infections can cause more minor problems, including common skin warts and verrucas.
How do people get HPV?
HPV is a sexually-transmitted infections.
In most cases a person will become infected after having vaginal and/or anal sex.
Men and women can also become infected through oral and other sex play.
In many cases a person will not realise they are infected, and can still have HPV years after coming into contact with an infected person.
In very rare cases a pregnant woman can pass HPV to her baby during delivery.
In these cases a child can develop recurrent respiratory papillomatosis (RRP), a rare condition where warts grow in the throat.
The HPV vaccine
A national vaccination programme for HPV is in place in the US and UK for girls aged 12 and 13.
Three injections are given within a 12-month period by a nurse.
The vaccine is given at a young age because it needs to be administered before a person comes into contact with HPV.
It has also been found to provide greater immune response in preteens, than it does in older teenagers and young women.
An official recommendation on whether to offer the HPV vaccine to all adolescent boys in the UK is expected in early 2017.
Clinical trials have showed the vaccines provide close to 100 per cent protection against precancers and for HPV4 - genital warts.
Since it was first recommended in 2006, there has been a 56 per cent reduction in HPV infections among teenage girls in the US.
Protection offered should be long-lasting, with trials showing the vaccine lasts in the body for at least 10 years.
HPV vaccination does not replace the need for regular cervical smear tests in women between the age of 25 and 65.
Source: NHS Choices and the CDC
