A sore throat, or pharyngitis, is pain or irritation felt in the throat that often worsens with swallowing. This common symptom usually signals an underlying infection. Since these infectious agents reside in the mouth and throat, a sore throat is often highly contagious. Direct contact, such as kissing, is an efficient way for germs to transfer, though contagiousness depends entirely on the specific cause of the inflammation.
What Causes a Sore Throat
The vast majority of sore throats (85 to 95 percent) are caused by viral infections. These include common cold viruses (rhinoviruses and adenoviruses), influenza, and the Epstein-Barr virus, which causes mononucleosis. Viral sore throats typically resolve on their own, requiring only supportive care for symptoms.
A smaller percentage are caused by bacteria, most commonly Group A Streptococcus (Streptococcus pyogenes). This bacterium causes strep throat, which requires antibiotic treatment to prevent serious complications like rheumatic fever. Identifying the cause is important, as bacterial and viral infections require different treatment approaches.
How Germs Spread Through Kissing and Close Contact
The germs that cause a sore throat are primarily spread through respiratory droplets and saliva. When an infected person coughs, sneezes, or talks, they release microscopic droplets into the air that others can inhale. Close contact facilitates this droplet transfer by minimizing the distance between people.
Kissing involves the direct exchange of saliva, making it a very efficient route for infection. Pathogens causing sore throats—both viruses and bacteria—reside in the throat and are present in high concentrations in the saliva. For example, the Epstein-Barr virus is so effectively spread this way that mononucleosis is commonly nicknamed the “kissing disease.”
When a Sore Throat is No Longer Contagious
The length of time a person remains contagious is determined by the type of infection and whether it is treated. For a sore throat caused by a common cold or flu virus, the person is contagious until their symptoms have fully resolved, usually taking five to seven days. However, the Epstein-Barr virus (mononucleosis) can persist in saliva and remain transmissible for weeks after initial symptoms disappear.
The timeline is more defined for a bacterial infection like strep throat, provided the person receives treatment. An individual with strep throat stops being contagious approximately 12 to 24 hours after starting an effective course of antibiotics. If strep throat is left untreated, the person can spread the bacteria for two to three weeks, even if their own symptoms start to improve.
Simple Steps to Limit Transmission
Consistent hygiene practices significantly reduce the spread of germs that cause sore throats. Frequent hand washing with soap and water removes pathogens acquired from contaminated surfaces or contact. Covering the mouth and nose when coughing or sneezing, ideally with a tissue or the elbow, helps contain infectious respiratory droplets.
Individuals with a sore throat should avoid sharing items that come into contact with saliva, such as eating utensils, drinking glasses, and toothbrushes. Temporarily avoiding kissing and other intimate contact until the contagious period has passed is the most direct way to prevent transmission.