Prevention Starts with the Transmission Route
Choose each prevention measure from the virus's transmission route. An action that interrupts one route may have little effect on another. A measure works when it blocks the step the virus actually uses to move between people.
Identify the Route before Choosing an Action
First determine how the virus spreads. The route may involve respiratory droplets, hands and surfaces, blood or body fluids, food and water, or a vector such as a mosquito. A vector is an organism that carries a pathogen from one host to another.
A measure aimed at the wrong route can miss its target. Draining standing water helps reduce mosquitoes that carry certain viruses, but it does not directly stop respiratory particles in a closed room. Masks address a different route and do not replace mosquito breeding-site control.
Viruses can spread through contact, droplets, air, blood or body fluids, and other routes. The route determines which measure can interrupt transmission.
Each Measure Targets a Point in Transmission
Respiratory measures target particles near the nose and mouth, shared air, and airflow. Contact measures target transfer through hands, surfaces, wounds, or mucous membranes. Measures for mosquito-borne viruses target bites and breeding sites.
A prevention measure must target a named step in the transmission route.
The table gives three common examples. Foodborne, waterborne, sexual, bloodborne, vertical, and other transmission routes require their own evidence-based controls.
| Transmission route | Point being interrupted | Example action | Common mistake |
|---|---|---|---|
| Respiratory particles in shared air | Nose, mouth, indoor air, and exposure time | Ventilation, distance, masks when risk fits, staying home when sick | Assuming one action is enough for every situation |
| Hands and surfaces | Movement from surfaces to hands, then eyes, nose, or mouth | Wash hands with soap, clean frequently touched surfaces | Cleaning objects while still touching the face often |
| Mosquito vector | Bites and mosquito breeding sites | Reduce standing water, prevent bites, manage the home environment | Using a respiratory-virus strategy for a mosquito problem |
Where Each Transmission Route Can Be Interrupted
Each transmission route can be interrupted at particular stages. Once the route is known, the reason for using masks, soap, vaccination, or vector control can be stated directly.
Respiratory and Contact Routes Need Different Measures
For respiratory spread, exposure risk depends on respiratory particles, ventilation, and time spent indoors. During contact spread, a virus can move when contaminated hands or surfaces touch the eyes, nose, mouth, or a wound. Mosquitoes transmit viruses when they bite, so prevention must also reduce breeding sites and prevent bites.
Prevention usually combines several measures suited to the transmission route. For respiratory viruses, distance, ventilation, masks during higher risk, and hand hygiene support one another. For mosquito-borne viruses, use standing-water control, bite prevention, and environmental monitoring.
Dengue viruses spread mainly through bites from Aedes mosquitoes, so prevention focuses on avoiding bites and controlling mosquitoes around homes. Prevention for respiratory viruses instead addresses particles released into shared air and close-range exposure.
How Soap Removes Dirt and Microbes
Hand hygiene removes dirt, oils, and microbes that may be too small to see. A soap molecule has one part that mixes well with water and another that binds to oil. Rubbing loosens the material, and rinsing carries it away from the skin.
Handwashing can physically remove both enveloped and non-enveloped viruses. Soap can also disrupt the lipid outer layer of enveloped viruses. Friction loosens soil and microbes, and running water carries them away. Physical removal and lipid-envelope disruption are complementary mechanisms. Because hands often move material from surfaces to the face, handwashing can interrupt this route.
Vaccines Trigger Immune Responses and Antivirals Inhibit Replication
A vaccine does not physically block droplets or aerosols in the air. After vaccination, the immune system develops a response that recognizes a specific pathogen. Depending on the vaccine and pathogen, protection against infection can be incomplete even when protection against severe disease is strong. Vaccines work through immunity, while masks, ventilation, and hygiene act on exposure and transmission.
An antiviral is a medicine that inhibits one or more stages of viral replication. Different antivirals target different viruses or replication steps, so a medicine used for one infection does not automatically work for another. Most antivirals are used for treatment. Some influenza antivirals can also be prescribed before or after exposure to reduce the chance of illness. A clinician must decide whether an antiviral is appropriate, and the medicine does not replace vaccination or measures that interrupt the transmission route.
The diagram below places each measure at the step it affects. Masks, ventilation, and hygiene reduce exposure along the relevant transmission route. Vaccination prepares the immune response, while antiviral medicines inhibit replication under medical guidance.
The Transmission Route Determines the Action
For mosquitoes, address breeding sites and bites. For contact spread, address hands, surfaces, and wounds.
Each action has a biological basis in the way a virus moves, enters a host, and replicates.