How long can viruses or bacteria survive in human saliva?

Viral and Bacterial Survival in Human Saliva

Viruses and bacteria can survive in human saliva from several hours to several days, depending on the specific pathogen and environmental conditions, with most respiratory viruses persisting for hours to a few days while certain bacteria can remain viable for days to weeks. 1, 2

Viral Persistence in Saliva

Enveloped Viruses (Including Coronaviruses and Influenza)

• Enveloped viruses like SARS-CoV-2, influenza, and other coronaviruses typically survive less than one week in saliva and bodily fluids, with most becoming non-infectious within hours to days when exposed to typical environmental conditions. 1
• These lipid-enveloped viruses are highly susceptible to environmental degradation and disinfectants, surviving probably less than one week indoors and even shorter periods (perhaps hours) when exposed to sunlight outdoors. 1
• SARS-CoV-2 has been consistently detected in saliva of infected patients (91.7% detection rate), with viral loads generally showing a declining trend over time. 3
• Hantaviruses in neutral solutions can persist for several hours at body temperature (37°C) and for several days at lower temperatures, though infectivity decreases substantially. 1

Respiratory Viruses

• Most respiratory tract viruses including coronavirus, coxsackievirus, influenza, and rhinovirus can persist on surfaces and in fluids for a few days. 2
• Herpes viruses (HSV-1, HSV-2, CMV) show variable persistence from only a few hours up to 7 days depending on conditions. 2

Blood-Borne and Gastrointestinal Viruses

• Blood-borne viruses like hepatitis B (HBV) or HIV can persist for more than one week in appropriate conditions. 2
• Gastrointestinal viruses such as hepatitis A, poliovirus, and rotavirus persist for approximately 2 months. 2

Bacterial Persistence in Saliva

Gram-Positive Bacteria

• Most gram-positive bacteria including Staphylococcus aureus (including MRSA), Enterococcus species (including VRE), and Streptococcus pyogenes can survive for months on dry surfaces and in dried biological fluids. 2
• These organisms are remarkably resilient and can serve as continuous sources of transmission without proper disinfection. 4, 2

Gram-Negative Bacteria

• Many gram-negative species including Acinetobacter, E. coli, Klebsiella, Pseudomonas aeruginosa, and Serratia marcescens can survive for months in appropriate conditions. 2
• However, some gram-negative bacteria like Bordetella pertussis, Haemophilus influenzae, and Vibrio cholerae persist only for days. 2

Spore-Forming Bacteria

• Mycobacteria including M. tuberculosis and spore-forming bacteria like Clostridium difficile can survive for months on surfaces and in dried materials. 2

Critical Environmental Factors Affecting Survival

Temperature Effects

• Temperature is the most important factor affecting pathogen survival—higher temperatures accelerate inactivation through protein denaturation and increased enzyme activity. 1
• Viral survival decreases substantially at body temperature (37°C) compared to room temperature or refrigerated conditions. 1

pH and Chemical Environment

• Human coronavirus 229E remains most stable at pH 6 at 33°C and maintains stability through pH range 5-8. 1
• SARS-CoV-2 survives in a wide pH range (3-10) without apparent loss for at least one hour. 1
• Hantaviruses show sensitivity to pH ≤5 but maintain infectivity in neutral solutions. 1

Presence of Other Microorganisms

• The presence of other bacteria in biological fluids accelerates viral inactivation compared to sterile conditions. 1
• Biofilms and microbial communities enhance pathogen decay rates. 1

Saliva-Specific Antiviral Properties

• Human saliva contains numerous antibacterial and antiviral proteins that actively reduce pathogen viability, with most antibacterial proteins displaying antiviral activity against specific viral pathogens. 5
• Salivary protein gp340 (salivary agglutinin) functions as a specific inhibitor of HIV-1 and influenza A infectivity when soluble in saliva. 5
• These innate immune factors in saliva contribute to reducing the infectious period of pathogens in the oral cavity. 5

Clinical Implications for Transmission Risk

High-Risk Periods

• Infected rodents shed hantavirus in saliva, urine, and feces for many weeks, though the exact duration and period of maximum infectivity remain unknown. 1
• For SARS-CoV-2, patients with active infection should avoid close contact for 10-14 days from symptom onset, as this represents the contagious period. 6

Transmission Routes

• Transmission occurs when infective saliva or excreta are inhaled as aerosols, directly introduced into broken skin, introduced onto conjunctivae, or possibly ingested in contaminated food or water. 1
• Healthcare workers can contaminate their hands or gloves by touching surfaces contaminated with saliva-borne pathogens, with sufficient organism numbers to result in patient transmission. 4

Common Pitfall to Avoid

Do not assume that all pathogens in saliva have similar survival times—enveloped viruses are generally much more fragile (hours to days) than bacteria and spore-forming organisms (days to months), requiring different infection control strategies. 1, 2

Human saliva represents a complex biological fluid where pathogen survival depends on the interplay of viral/bacterial characteristics, temperature, pH, presence of antimicrobial proteins, and competing microorganisms. 1, 5