Scientists at Duke University in North Carolina have found a way to use the polio virus as a weapon against glioblastoma, the most common and most aggressive form of brain cancer. To do so, they genetically modified the virus so that it could only multiply in tumour cells, not in healthy tissue. The virus created as a result, known as PVS-RIPO, is injected directly into the tumour (area shaded red, above). The virus then fights the cancer in two ways: it directly destroys the tumour cells and stimulates the immune system to find and attack the infected cancer cells. The therapy was first tested on humans in 2011 and has already achieved promising results.
How long can a virus survive without a host? Most viruses can only remain active for a few hours outside of a host, but the norovirus (above) is a survivor – the vomiting bug has been found on a carpet after 12 days. The virus can also withstand extreme climates, existing happily in a temperature range of minus 20 to plus 60 degrees Celsius. Added to that, the norovirus is also extremely mutable, as well as highly adaptable. Every two to three years a new strain develops, making it impossible for researchers to develop a vaccine against the pathogen.