Infectious vs. Contagious
Diseases can be caused by microorganisms such as bacteria and viruses and the entrance of these into the body, and the resultant development of a disease, is known as an infection. When the disease is able to be passed onto another human being directly the infection is also contagious. Some infections can also be passed on indirectly through the sharing of an object, with measles and chickenpox common examples of diseases transmitted by direct person to person contact or contact with an object touched by an infected person.
Other disease can be caught through contact with an insect, rodent, dog, cat, or other animal often due to bacteria or viruses in their faeces, urine, in cyst-form on their fur, or through a bite or scratch. Malaria and Lyme disease are both examples of vector-borne infections transmitted by mosquitoes and ticks respectively. Lyme disease is not contagious in the traditional sense however as it requires a tick bite from an infected tick for a person to become infected with Borrelia bacteria.
Some diseases are infectious, contagious through direct contact, and contagious through indirect contact such as through an object touched by both parties. Flu, the common cold, and a number of other viral infections are often transmitted through handshakes, kissing, or simply being in the room when an infected person sneezes. These types of infectious diseases are water-borne, air-borne, or both, making it hard to defend against them. One thing to note however is that not all those exposed to such viruses or bacteria will become infected; some people have stronger immune systems and the conditions may not be right for the infection to take hold. Other infections are spread through specific types of contact, such as the AIDS virus which is not (normally) passed on through kissing or touching but is still contagious through other forms of bodily contact. This would be described as being less contagious than the common cold but is a more serious infection.
Lyme Disease Infection Prevention
As a very general rule, not all infectious diseases are contagious but all contagions are infectious. The degree to which an infection is contagious makes a difference when considering how to halt the spread of the disease, which is why those working in the field of Lyme disease prevention tend to concentrate their efforts on reducing tick exposure, rather than by telling those with Lyme disease to avoid contact with others until free of the infection. Of course, it is important to note that when suffering from an infection such as Lyme disease it may be that the immune system is more vulnerable to other types of infection, including those that are contagious, and so patients with Lyme disease may wish to avoid overt situations where they are in contact with others infected with contagious diseases, at least until they are free of Lyme disease and back in good health.
Lyme Disease Transmission via Bodily Fluids
Lyme disease bacteria have to have a way to travel between people if they are to infect another and the spirochaetes are rarely found in bodily fluids and are unlikely to survive in such fluids. Instead, the bacteria tend to be found in tissue, meaning that contagion is extremely limited except in unusual circumstances, such as organ transplants without first screening for infection. There have been documented cases of placental transmission of untreated Lyme disease, with the likelihood of miscarriage found to increase in cases of maternal Lyme disease infection (at least in animal research). Transmission of Lyme disease in breastmilk is extremely unlikely and no proven cases have been documented, despite some reports by patients. It is thought that the spirochaetes are unable to survive in such fluid.
Lyme Disease Bacteria – Special Needs for Infection
Another reason that Lyme disease is infectious rather than contagious is that the bacteria appear to need specific conditions for successful transmission between hosts. Lyme disease bacteria have an outer protein coating that can evade detection by the hosts’ immune system by making itself look similar to the hosts’ own tissues. This takes time to do and so direct transmission through a fleeting exposure between humans is unlikely to result in infection as any bacteria that do make the jump between people are likely to simply be killed by the person’s immune system. Tick bites provide the perfect opportunity for prolonged exposure to the person’s immune system and the rearrangement of outer proteins in the bacteria to avoid detection upon transmission. Even when bitten by a tick it is usually the case that the tick must be in place for 24hrs before the bacteria are transmitted, making quick tick removal important in Lyme disease prevention.
Is Lyme Disease Contagious?
Lyme disease bacteria are not able to survive for long in saliva, mucus, or other bodily fluids such as semen as they need a nutrient-rich environment in which to live. Transfer of Lyme disease via sexual contact, kissing, or sharing of cutlery, towels, or other objects is, therefore, almost impossible. It is likely however that people in the same family, or household, contract Lyme disease infections together but this is thought largely to be due to frequenting the same areas where ticks may reside, or having a tick brought into the house on one person, or a family pet, and the same tick infecting more than one person.
In answer to the question ‘Is Lyme disease infectious?’ there is a resounding Yes, it is not, however, contagious in the traditional sense.