Varicella vaccine from a child with natural varicella, introduced into human embryonic lung cell cultures, adapted to and propagated in embryonic guinea pig cell cultures, and finally propagated in human diploid cell cultures. Japan was among the first countries to vaccinate for chickenpox. The vaccine was first licensed in the United States in 1995. Routine vaccination against varicella zoster virus is also performed in the United States, and the incidence of chickenpox has been dramatically reduced there (from 4 million cases per year in the pre-vaccine era to approximately 400,000 cases per year as of 2005). In Europe most countries do not
Motor neuron disease Motor neuron disease Motor neuron diseases (MNDs) are a group of neurodegenerative disorders that selectively affect motor neurons, the cells which control voluntary muscles of the body. Commonly, the following disorders are counted among motor neuron diseases: The term “motor neuron disease” sometimes refers to ALS, but in this article, the term refers to a group of diseases listed above, which includes ALS. Motor neuron diseases affect both children and adults. While each motor neuron disease affects patients differently, they all cause movement-related symptoms, mainly muscle weakness. Most diseases seem to occur randomly without known causes, but some forms are