How do environmental factors (e.g., temperature, humidity) affect the survival of the mumps virus?

Alright, to explain how environmental factors affect the mumps virus, let's use an analogy.

You can imagine the mumps virus as a tiny, tiny "seed." For it to survive and "sprout" (i.e., infect others), it needs a suitable environment. If the environment is too harsh, it will die off on its own.

The main factors affecting its survival are the commonly discussed temperature and humidity.

1. Temperature: Sensitive to Heat, Resilient to Cold

The mumps virus has a distinct characteristic: it can survive for quite a long time in low temperatures but is very sensitive to heat.

• Low-temperature environments (e.g., winter): For the virus, it's like entering a "refrigerator." In environments below 0°C, it can survive for several months, retaining its infectivity. This is one reason why mumps outbreaks are more common in winter and spring, as the virus can survive longer in cold, dry air, increasing opportunities for transmission.
• Room temperature environments: At room temperature (e.g., around 20°C), it can also survive for a day or two. If it lands on tables, doorknobs, or toys and isn't cleaned promptly, someone touching these surfaces and then their mouth or nose within this period could get infected.
• High-temperature environments: This is the virus's "natural enemy." As long as the temperature exceeds 55°C, it will be inactivated within 20 minutes. If you use boiling water (100°C) to scald something, it's almost instant inactivation. Therefore, high-temperature disinfection (e.g., scalding dishes with boiling water) is very effective against it.

In short: The colder it is, the more resilient the virus; the hotter it is, the faster the virus dies.

2. Humidity: Dry Air is Its "Accomplice"

Humidity primarily affects the virus's ability to spread through the air. The virus is usually encased in droplets expelled when an infected person sneezes or coughs.

• Dry air (low humidity): After droplets are expelled, their moisture quickly evaporates, leaving behind smaller, lighter "viral particles" (droplet nuclei). These tiny particles can float in the air like dust for a long time and travel further. This significantly increases the chance of others inhaling them.
• Humid air (high humidity): Droplets retain more moisture, become heavier, and quickly fall to the ground or surfaces, making it difficult for them to remain suspended in the air for long. While this reduces the risk of airborne transmission, it might increase the risk of contact transmission (e.g., touching a surface contaminated with the virus).

In short: The drier the air, the more easily the virus "roams around" in the air, spreading over a wider range.

In Summary

Overall, the mumps virus prefers "cold and dry" environments. This perfectly explains why it is particularly active in the cold and dry winter and spring seasons in northern regions.

What Can We Do?

Knowing its weaknesses, we can easily combat it:

1. Ventilate frequently: Keep the air flowing to blow away any viruses that might be suspended indoors, reducing the indoor viral concentration.
2. Get more sunlight: The ultraviolet rays in sunlight are natural disinfectants and have a strong killing effect on viruses.
3. Maintain cleanliness: For items touched by infected individuals, wiping them with a chlorine-based disinfectant or scalding them with boiling water can effectively kill the virus.
4. Humidify appropriately: During dry seasons, using a humidifier can help reduce the time the virus remains suspended in the air.

Hope this explanation helps you understand!