How Long Can Rabies Virus Survive in Saliva Under Different Conditions?

Rabies virus activity issues?

Hello, Doctor.
I would like to ask how long saliva containing the rabies virus remains infectious in a typical air-dry environment at room temperature.
Does saliva with the rabies virus lose its infectivity within a few minutes (not exceeding one hour) due to the virus's anaerobic nature? Additionally, if an environment is kept consistently moist but exposed to air (with oxygen), can the rabies virus survive in that environment for more than a day? Thank you, Doctor.

Niming, 20~29 year old female. Ask Date: 2020/10/10

Dr. Xiao Yongxun reply Family Medicine

Dear Sir/Madam,
1.
The rabies virus (Rabies virus) is an RNA virus belonging to the Lyssavirus genus and is the causative agent of rabies.
The complete rabies virus has a bullet-shaped morphology, measuring approximately 200 nm in length and about 70 nm in diameter.
It is an enveloped virus, with the envelope composed of a lipid bilayer and matrix protein M forming the structural protein shell.
The core within the envelope is the nucleocapsid (Nucleocapsid, NC), which consists of a single-stranded, non-segmented negative-sense RNA along with nucleoprotein N, phosphoprotein P, and polymerase L.
The RNA encodes five structural proteins: nucleoprotein N, phosphoprotein P, matrix protein M, glycoprotein G, and polymerase protein L.
The rabies virus is relatively sensitive to heat, ultraviolet light, sunlight, and desiccation, and can be inactivated by strong acids, strong bases, formaldehyde, iodine, acetic acid, ether, soap solutions, and both ionic and non-ionic detergents.
Clinically, surfactants and disinfectants (such as formaldehyde, mercuric chloride, and iodine tincture), acidic or basic agents, high temperatures, or ultraviolet light are commonly used to inactivate the virus.
2.
The rabies virus must parasitize the nerve cells of mammals, and it is secreted in cerebrospinal fluid, saliva, or bodily fluids.
Clinically, it does not exhibit characteristics typical of bacteria, such as being aerobic or anaerobic.
3.
The rabies virus requires the protection of its envelope; if it is removed from mammals, any of the aforementioned harsh environments or substances that disrupt the envelope and proteins will render it unable to survive.
In other words, as long as the envelope remains intact, the virus can survive for an extended period.
If there are sufficient viable viruses, they can still cause infection in mammals when the opportunity arises.
This is why it is advised not to touch dead wild animals, to avoid the risk of rabies virus transmission.
4.
My knowledge is limited, and the details you mentioned may require consulting specialized books or research reports, or even virologists, to fully address your inquiries.

Reply Date: 2020/10/10

More Info

The rabies virus, a member of the Lyssavirus genus, is primarily transmitted through the saliva of infected animals, particularly through bites. Understanding its survival in various environments is crucial for assessing the risk of transmission and implementing preventive measures.

1. Survival in Dry Air: Under normal room temperature and dry conditions, the rabies virus in saliva can survive for a limited time. Studies indicate that the virus can remain viable for several hours to a few days, depending on environmental factors such as temperature and humidity. However, in dry air, the virus's viability decreases significantly. The rabies virus is sensitive to desiccation, meaning it loses its infectivity more quickly in dry environments compared to moist conditions.

2. Anaerobic Conditions: The rabies virus is not strictly anaerobic; it does not require an oxygen-free environment to survive. However, it is sensitive to environmental stresses. While it may lose activity relatively quickly in dry conditions, it does not necessarily become inactive within minutes. The exact timeframe for loss of infectivity can vary, but it is generally understood that the virus can remain active for several hours in saliva, even in the presence of oxygen.

3. Survival in Moist Environments: In a humid environment, the rabies virus can survive longer than in dry conditions. If the environment is kept moist and exposed to air, the virus may remain viable for more than a day. The moisture helps preserve the viral structure, allowing it to maintain infectivity. However, factors such as temperature and exposure to sunlight can still affect its survival. For instance, the rabies virus is susceptible to heat and ultraviolet light, which can inactivate it relatively quickly.

4. Inactivation Methods: The rabies virus is sensitive to various disinfectants and environmental conditions. It can be inactivated by exposure to high temperatures (above 56°C), ultraviolet light, and certain chemical agents like formaldehyde and bleach. This is why proper cleaning and disinfection of surfaces that may have come into contact with saliva from potentially infected animals are critical in preventing transmission.

5. Practical Implications: Given the rabies virus's ability to survive in saliva for extended periods, it is essential to exercise caution in environments where exposure to potentially infected saliva may occur. If you suspect that surfaces or objects may have been contaminated, it is advisable to disinfect them thoroughly. If disinfection is not possible, allowing time for the virus to lose its viability—typically a few days—can help reduce the risk of transmission.

In summary, while the rabies virus can survive for several hours to days in saliva under various conditions, its viability is significantly influenced by environmental factors such as humidity, temperature, and exposure to disinfectants. Understanding these factors is crucial for preventing rabies transmission and ensuring public health safety. Always consult healthcare professionals for guidance on rabies exposure and preventive measures.

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