The concept that all human samples are potentially infectious is called:
Universal precautions, now incorporated into Standard Precautions, embodies the principle that all human blood, body fluids except sweat, unfixed tissues, organs, and cell cultures should be regarded as infectious regardless of donor history or test results. Concept formalized by CDC in 1987 during HIV epidemic to protect healthcare and laboratory workers from occupational transmission. Rationale is that serological window periods, asymptomatic carriers, and unknown agents prevent absolute assurance of safety. Implementation requires barrier protection including gloves, laboratory coats, face masks and goggles when splashing anticipated, hand hygiene after glove removal, prohibition of mouth pipetting, safe handling and disposal of sharps in puncture-resistant containers, decontamination of work surfaces with EPA-approved disinfectants, use of biosafety cabinets for manipulations that may create aerosols, and prompt reporting of exposures. Training, medical surveillance, and availability of post-exposure prophylaxis complete program. This doctrine justifies treating routine cell culture as BSL-2 and underpins OSHA Bloodborne Pathogens Standard 29 CFR 1910.1030.
Ref: CDC Universal Precautions for Preventing Transmission of Bloodborne Infections, MMWR 1988; OSHA 29 CFR 1910.1030. https://www.cdc.gov/mmwr