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Salem Health: Infectious Diseases & Conditions, 2nd Edition

Horizontal disease transmission

by Janet Ober Berman, , M.S., CGC

Category: Transmission

Definition

Horizontal disease transmission refers to the passing of a disease or pathogen from one person to another who are in the same generation. The disease is not passed from woman to fetus in the perinatal period; this is done through vertical disease transmission. Symptoms depend on the specific type of acquired infection. Horizontal disease transmission occurs by direct or indirect pathogenic contact.

Routes of Transmission

Horizontal transmission arises by direct contact through touching or sharing of saliva and secretions. For example, if one sexual partner has an infection, that infection may be transmitted to another partner through genital, anal, or oral contact. More than twenty-five sexually transmitted diseases (STDs) exist, including human immunodeficiency virus (HIV) infection, chlamydia, gonorrhea, and herpes. The respiratory route is another common pathway for direct contact, whereby an infected person coughs or sneezes droplets onto a susceptible person. The pathogen enters the body through the nose, mouth, or eye and causes infections such as influenza, chickenpox, and strep throat.

Indirect transmission occurs when a person has contact with an object (fomite) or host that carries the pathogen, allowing transmission without physical contact. Infections that are spread by contact with inanimate contaminated objects are warts, syphilis, and impetigo. Risk factors include improper handwashing technique, inadequate sterilization of objects, and living in close quarters, especially under unsanitary conditions. Indirect contact with insects or animals acting as disease vectors will also lead to horizontal disease transmission. Mosquitoes transfer malaria and ticks transfer Lyme disease to humans.

Testing and Prevention

Laboratory blood work or a physical exam, or both, will diagnose a horizontally transmitted disease. Antibiotics, antiviral medications, and vaccinations are available for some infections. In the case of STDs, precautions such as abstinence or condom use help prevent future horizontal transmission. One should also clean soiled laundry and bath towels and should avoid sharing personal toiletries.

Impact

Prevention of horizontal disease transmission is of paramount importance from a public health perspective. One study estimated there are 333 million new cases of syphilis, gonorrhea, trichomoniasis, and chlamydia in one year worldwide, with HIV remaining prevalent in both developed and developing countries. If not adequately controlled, some infections can cause global pandemics, such as the H1N1 influenza outbreak. In addition, the financial impact of any pandemic is extremely high.

Further Reading

1 

Martinson, Francis E., et al. “Risk Factors for Horizontal Transmission of Hepatitis B Virus in a Rural District in Ghana.” American Journal of Epidemiology 147 (1997): 478-487.

2 

Okinyi, M., et al. “Horizontally-Acquired HIV Infection in Kenyan and Swazi Children.” International Journal of STD and AIDS Online 20 (2009): 852-857.

3 

Wilkinson, D., and G. Rutherford. “Population-Based Interventions for Reducing Sexually Transmitted Infections, Including HIV Infection.” Cochrane Database of Systematic Reviews (2001): CD001220. Available through EBSCO DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.

Citation Types

Type
Format
MLA 9th
Berman, Janet Ober. "Horizontal Disease Transmission." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0282.
APA 7th
Berman, J. O. (2020). Horizontal disease transmission. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Berman, Janet Ober. "Horizontal Disease Transmission." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed September 16, 2025. online.salempress.com.