How long does a virus live in hostile environment outside the host?

The survival time of viruses outside the host can vary greatly depending on the virus type, environmental conditions, and the specific surrounding material or substrate. Here's a general overview, although actual survival times can differ:

1. Non-enveloped Viruses:

- Non-enveloped viruses are usually hardier and more resistant to environmental stresses. Some examples include adenoviruses, noroviruses, and rotaviruses.

- On surfaces, they can survive from several hours to a few days, sometimes even weeks, depending on the surface and temperature.

- In water or sewage, they can persist for weeks or sometimes even months.

2. Enveloped Viruses:

- Enveloped viruses have a lipid membrane that surrounds the virus particle. This membrane can be more fragile. Examples include influenza viruses, HIV, and SARS-CoV-2 (the virus that causes COVID-19).

- On surfaces, enveloped viruses generally survive for shorter periods than non-enveloped viruses. They may last from several minutes to hours or a few days, based on the specific virus and conditions.

- In water or sewage, enveloped viruses can generally survive for shorter durations compared to non-enveloped viruses.

External factors can significantly affect viral survival. For example:

- Temperature: Viruses can generally tolerate a wide range of temperatures, but temperature extremes (very high or very low) can reduce their infectivity more rapidly.

- Humidity: Low humidity can be more favorable for viral survival, as it allows the virus particles to remain airborne for longer periods. High humidity can promote particle clumping and reduce infectivity.

- Sunlight (UV radiation): Direct exposure to sunlight can be harmful to viruses, causing damage to the viral structure and RNA/DNA. Sunlight exposure can significantly reduce the infectivity of many viruses.

- Other environmental factors: Factors like pH, salt concentration, and the presence of organic matter can also impact viral stability.

It's important to note that the survival time of viruses outside the host is influenced by many complex factors, and these estimations are generalizations based on current understanding. Effective handwashing, environmental cleaning, and avoiding contact with contaminated surfaces and respiratory droplets can help minimize the risk of viral transmission, especially in the case of enveloped viruses.