But occasionally, when a new flu strain emerges, a pandemic results in a faster spread of disease and, often, higher mortality rates. Dengue virus first appeared in the s in the Philippines and Thailand and has since spread throughout the tropical and subtropical regions of the globe, according to Clinical Microbiology Reviews.
A vaccine for Dengue was approved in by the U. Food and Drug Administration for use in children years old living in areas where dengue is common and with a confirmed history of virus infection, according to the CDC.
In some countries, an approved vaccine is available for those years old, but again, recipients must have contracted a confirmed case of dengue in the past. Those who have not caught the virus before could be put at risk of developing severe dengue if given the vaccine. Two vaccines are now available to protect children from rotavirus, the leading cause of severe diarrheal illness among babies and young children.
The virus can spread rapidly, through what researchers call the fecal-oral route meaning that small particles of feces end up being consumed.
Although children in the developed world rarely die from rotavirus infection , the disease is a killer in the developing world, where rehydration treatments are not widely available.
The WHO estimates that worldwide, there are more than 25 million outpatient visits and two million hospitalizations each year due to rotavirus infections. Countries that have introduced the vaccine have reported sharp declines in rotavirus hospitalizations and deaths. The virus likely emerged in bats initially, then hopped into nocturnal mammals called civets before finally infecting humans, according to the Journal of Virology.
After triggering an outbreak in China, SARS spread to 26 countries around the world, infecting more than people and killing more than over the course of several months, according to History.
The disease causes fever, chills and body aches, and often progresses to pneumonia, a severe condition in which the lungs become inflamed and fill with pus.
SARS has an estimated mortality rate of 9. The virus may have originated in bats and passed through an intermediate animal before infecting people, according to Nature. The initial outbreak prompted an extensive quarantine of Wuhan and nearby cities, restrictions on travel to and from affected countries and a worldwide effort to develop diagnostics, treatments and vaccines.
Since its appearance, the virus has caused over five million deaths worldwide, according to Reuters. Common symptoms include fever, cough, loss of taste or smell and shortness of breath and more serious symptoms include breathing difficulties, chest pain and loss of mobility.
On Aug. In December , this vaccine became the first to be approved after a large clinical trial, according to Nature. According to WHO , the disease infected camels before passing into humans and can trigger a fever, coughing and shortness of breath in infected people.
CDC routinely collects viruses through a domestic and global surveillance system to monitor for changes in influenza viruses. CDC also works with the state public health departments and World Health Organization to collect additional information on antiviral resistance in the United States and worldwide.
The information assists CDC in making informed recommendations for treatment and prevention of influenza in the United States. To receive weekly email updates about Seasonal Flu, enter your email address:. Skip directly to site content Skip directly to page options Skip directly to A-Z link. Influenza Flu. Section Navigation. Facebook Twitter LinkedIn Syndicate. Summary of the Influenza Season. Minus Related Pages. On This Page. What CDC Does.
To receive weekly email updates about Seasonal Flu, enter your email address: Email Address. What's this? The FBI led a nine-year investigation on how anthrax got in those letters, and concluded the powder came from a research lab. Severe Acute Respiratory Syndrome, a viral respiratory illness caused by a coronavirus, was first diagnosed in Asia in February of , later reaching the U.
Common symptoms included high fevers, coughing and shortness of breath. A total of 8, people worldwide became sick, with only eight of those cases being in the U. The U. Mumps spread through close-contact activities such as sports, dancing, kissing, etc. From to , the largest outbreak reported 3, cases in a close-knit religious community in New York City after an infected student returned from the UK where there was another outbreak. Notable symptoms include fever, puffy cheeks and a swollen, tender jaw.
Escherichia coli was first reported in the U. The following year, Taco Bell was linked to E. The contraction of E. In , 49 cases in multiple states were linked to consuming Kroger Beef and in raw cookie dough was the culprit. However, the most infamous outbreak occurred in where a total of 58 cases were reported in 14 states. In , tomatoes were linked to Salmonella for a total of cases in 21 states. The list of foods linked to salmonella ranged from cantaloupe, peanut butter, raw chicken to even pet food.
The further apart viruses are on the horizontal axis of a phylogenetic tree, the more genetically different the viruses are to one another. An influenza clade or group is a further subdivision of influenza viruses beyond subtypes or lineages based on the similarity of their HA gene sequences.
See the Genome Sequencing and Genetic Characterization page for more information. Clades and subclades are shown on phylogenetic trees as groups of viruses that usually have similar genetic changes i. Dividing viruses into clades and subclades allows flu experts to track the proportion of viruses from different clades in circulation. Note that clades and sub-clades that are genetically different from others are not necessarily antigenically different. These proteins act as antigens. Antigens are molecular structures on the surface of viruses that are recognized by the immune system and can trigger an immune response such as antibody production.
Therefore, for antigenically different viruses, immunity developed against one of the viruses will not necessarily protect against the other virus as well.
Influenza A H3N2 viruses also change both genetically and antigenically. Influenza A H3N2 viruses have formed many separate, genetically different clades in recent years that continue to co-circulate.
Similar to influenza A viruses, influenza B viruses can then be further classified into specific clades and sub-clades. Influenza B viruses generally change more slowly in terms of their genetic and antigenic properties than influenza A viruses, especially influenza A H3N2 viruses. Influenza surveillance data from recent years shows co-circulation of influenza B viruses from both lineages in the United States and around the world.
However, the proportion of influenza B viruses from each lineage that circulate can vary by geographic location and by season.
0コメント