If there is one piece of advice that Nobel laureate Harald zur Hausen gives to young scientists, it is to pay no heed to sceptics.
The 81-year-old German scientist, who was in Singapore last month for the Global Young Scientists Summit, won the Nobel Prize in medicine in 2008, for discovering the human papillomaviruses (HPV) that cause cervical cancer.
Professor zur Hausen had his fair share of critics when he first postulated that cervical cancer could be caused by HPV.
Hence, the advice comes from personal experience.
"When you start something new, you always get some negative responses from your peers telling you it's nonsense... And I think, in some instances, it's quite good not to listen too carefully," said Prof zur Hausen.
When you start something new, you always get some negative responses from your peers telling you it's nonsense... And I think, in some instances, it's quite good not to listen too carefully.
PROFESSOR HARALD ZUR HAUSEN, on the challenges of scientific work.
"This happened to us for the papillomavirus work for quite a long period of time. "
At the time, many people did not believe that viruses could cause cancer at all, while others were focusing on the herpes simplex virus as the cause of cervical cancer.
Prof zur Hausen demonstrated in 1983 that cervical cancer in humans is caused by certain types of papillomaviruses.
When genes of these viruses are incorporated into the DNA of host cells, they cause their functions to go out of whack and contribute to tumour formation.
The scientist, who is currently professor emeritus at the German Cancer Research Centre in Heidelberg, Germany, said, in the late 1960s,the herpes simplex virus was believed to be the culprit behind cervical cancer because, based on animal studies, it had caused tumours.
But Prof zur Hausen felt that something was amiss - he could not detect the virus in all the DNA samples he tested.
He turned his attention to genital warts because they were shown to contain HPV, and was able to isolate and identify the HPV.
"I did a lot of literature work trying to find out what could be the reason and I found out there existed some reports on genital warts which converted to malignant tumours.
"It's not frequent but it happened, and I thought that is a good hint," said the virologist.
Prof zur Hausen then set out to identify the virus in genital warts.
However, in 1979, the first isolate his group got was HPV Type 6 - a "disappointment" as it was not found in cervical cancer.
But he did not give up. And he was able to use similar molecular methods to find HPV Type 11 and later, 16 and 18. HPV types 16 and 18 are responsible for about 70 per cent of cervical cancers worldwide.
According to the World Health Organisation, HPV infection is the most common viral infection of the reproductive tract.
There are 100 types of HPV, of which at least 13 are cancer-causing. Most sexually active women and men will be infected at some point in their lives.
Prof zur Hausen, who started his work on HPV in 1972, said with a laugh: "It took us about 11 years before we isolated the right types for cervical cancer... But I originate from an area of Germany (Gelsenkirchen) where people are very stubborn."
Today, his work has benefited many people worldwide.
The identification of the HPV types led the way for the HPV vaccine, which provides at least 70 per cent protection from HPV types 16 and 18.
Prof zur Hausen's work has not stopped.
Since 2008, he has been investigating the association between red meat and cancer - a project he and his wife, Professor Ethel-Michele de Villiers, 69, are both working on.
Their team has so far identified and isolated the DNA sequences of 22 virus-like infectious agents from cow serum and milk.
These have been shown to be capable of infecting human cells and could therefore increase a person's risk of getting infected with diseases such as multiple sclerosis, colon cancer and breast cancer.
The ultimate aim is to protect humans against these viruses by developing a vaccine that can be given to newborn cattle, Prof zur Hausen said.
For now though, he noted, avoiding red meat or dairy products such as milk makes no sense, since almost everyone has probably been exposed to products such as dairy milk from a young age.
The only advice he gives for now is for mothers to breastfeed their children for at least six months if possible, as breast milk has been shown to contain sugar that prevents the uptake of such viruses.