Can the rabies virus survive outside the host animal? Like if a rabid animal drools on grass, can it still remain infectious?
First things first: Rabies is an extremely dangerous infection and regular vaccination (every 10 years) is the only sure protection! As far as I know there are about 15 - 20 people who have ever survived an acute rabies infection in the history of human medicine, none of them without severe neurological sequelae and most of them died a few months after. The first reported case of a survival was Jeanna Giese in 2004.
Now to your question:
Technically viruses are not alive in the biological sense, so medical scientists speak of viruses being active (alive, infectious) or inactive (dead, destroyed, unable to infect a cell).
Yes, the rabies virus can stay active outside of a host body for a limited time, depending on environmental factors.
This German veterinary gives the following information:
- The virus occurs in the body fluids like saliva, blood, urine and milk of infected animals. To infect a new host, a certain number of viruses has to be transmitted and infections seem only possible by direct contact of infected saliva to mucosa or fresh wounds.
- Indirect contact (an infected animal leaves saliva on an object which is then touched by a healthy human) is very unlikely but not excluded to cause infections.
- The virus becomes inactive within one day in dry conditions and under UV light (natural sunlight).
- It can be inactivated by temperatures above 50°C / 122°F in a few minutes of time
- It can stay active and infectious for several days in a dark, humid environment around 23°C / 73°F.
In addition, the safety data sheet of MSDS Online contains the following information about the virus:
- Rabies virus is inactivated by exposure to 70% ethanol, phenol, formalin, ether, trypsin, β-propiolactone, and some other detergents.
- Rabies virus does not tolerate pH below 3 or above 11, and is inactivated by ultraviolet light.
- This virus does not survive well outside its host (in dried blood and secretions) as it is susceptible to sunlight and desiccation.
- When the virus was spread in a thin layer onto surfaces like glass, metal or leaves, the longest survival was 144 hours at 5 °C / 41°F (that's 6 full days!)
- At 20°C / 68°F, the virus was infective for 24h on glass and leaves and 48h on metal.
- At 30°C / 86°F, the virus was inactivated within 1.5h with exposure to sunlight and 20h without sunlight.