In some cases, these vaccines use epitopesâthe very specific parts of the antigen that antibodies or T cells recognize and bind to. Because subunit vaccines contain only the essential antigens and not all the other molecules that make up the microbe, the chances of adverse reactions to the vaccine are lower.
Tornadoes occur in many parts of the world, including Australia, Europe, Africa, Asia, and South America. Even New Zealand reports about 20 tornadoes each year. Two of the highest concentrations of tornadoes outside the U.S. are Argentina and Bangladesh.
Tornadoes have been observed on every continent other than Antarctica but there are areas which have a higher occurrence than others. The US has the most tornadoes annually, normally between 800-1000 a year; many of these occur in 'Tornado Alley', this area includes the states of Oklahoma, Texas, Kansas, Nebraska. tornado is defined as a 'violently rotating column of air which is in contact with the ground' (NWS). The word tornado is derived from the Spanish word tornar (to turn) and the Spanish word tronada (thunderstorm).