other matters for investigation are : methods for quantitatively detecting viruses adsorbed on solids , the virus-removal capability of soils , better virus indicators , virus concentration in shellfish , the frequency of infection in man brought about by swallowing small numbers of viruses in water , the epidemiology of virus infection in man by the water route , the effect of viruses of nonhuman origin on man , and the occurrence of tumour-inducing agents in water .
C0009450
infection
C0042769
virus