From the Guidelines
The transmission rate of Leprosy (Hansen's disease) is relatively low, with only about 5-10% of people who come into prolonged, close contact with untreated leprosy patients developing the disease. This is because leprosy is transmitted primarily through respiratory droplets from the nose and mouth during close, frequent contact with untreated infected individuals 1. The bacterium Mycobacterium leprae has a long incubation period, typically 3-5 years but can range from 1-20 years, which makes tracking transmission difficult.
- Key factors that contribute to the low transmission rate include:
- Natural immunity: Most people (approximately 95%) have natural immunity to leprosy
- Limited contagiousness: The disease is not highly contagious and is not spread by casual contact such as handshakes, sitting next to someone, or sexual contact
- Effective treatment: Once a person begins appropriate antibiotic treatment, they quickly become non-infectious, usually within a few days, even though treatment must continue for 6-24 months to fully eliminate the bacteria.
- Risk factors for transmission include:
- Living in close quarters with untreated patients
- Genetic susceptibility
- Compromised immune systems It's worth noting that the provided study 1 does not directly address the transmission rate of leprosy, but rather discusses the prevalence of HCV in high-risk groups, including leprosy patients. However, based on general medical knowledge, the low transmission rate of leprosy is well-established, and the disease is considered to be not highly contagious.
From the Research
Transmission Rate of Leprosy
The transmission rate of leprosy, also known as Hansen's disease, is not explicitly stated in the provided studies. However, the studies suggest that the disease is still being transmitted, and the annual new case detection rate has remained relatively static over the past decade 2, 3.
Factors Influencing Transmission
Several factors influence the transmission of leprosy, including:
- Close contact with infected individuals, likely through infectious aerosols created by coughing and sneezing, or possibly through direct contact 4, 5
- Living in endemic areas with high incidence rates 6, 3
- Presence of animal reservoirs, such as the nine-banded armadillo in the Americas, and potentially red squirrels in the British Isles 5
Prevention and Control Measures
To prevent and control the transmission of leprosy, the following measures have been proposed:
- Targeted chemoprophylaxis of contacts, using single-dose rifampicin or other antileprosy drugs 2, 3
- Development of new multidrug chemoprophylactic regimens using second-line antileprosy drugs 3
- Use of a simple, highly sensitive, and specific serological test to detect subclinical cases at the field level 3
- Implementation of a One Health transdisciplinary research approach to better understand the intricate picture of leprosy transmission 5
Current Challenges
Despite efforts to control and prevent leprosy transmission, several challenges remain, including: