Influenza virus toxins

The virus could continue to change to allow it to spread more easily in its new host, and widespread illness and death could result. Virus shift can also occur when an avian strain becomes adapted to humans, so that the avian virus is easily transmitted from person to person.

In this case, the avian strain jumps directly from birds to humans, without mixing or reassortment of the genetic material of influenza strains from different species. Influenza epidemics , also known as seasonal flu, occur annually and are the most common emerging infection among humans.

These epidemics have major medical impacts, but they are generally not fatal except in certain groups such as the elderly. Pandemics , on the other hand, happen once every few decades on average. They occur when a new subtype of influenza A arises that has either never circulated in the human population or has not circulated for a very long time so that most people do not have immunity against the virus.

The new subtype often causes serious illness and death, even among healthy individuals, and can spread easily through the human population. The flu, caused by a strain of H1N1, was by far the most deadly. More than , people died in the United States as a result of the Spanish flu, and up to 50 million people may have died worldwide. Nearly half of those of those deaths were among young, otherwise healthy individuals. The pandemic was due to a new H2N2 strain of influenza virus that caused the deaths of two million people, while the pandemic resulted from an H3N2 strain that killed one million people.

One pandemic has occurred so far in the 21st century. This was due to the novel swine-origin H1N1 virus which emerged in The WHO established a six phase pandemic alert system in in response to the potential threat of the H5N1 avian influenza virus. The alert system is based on the geographic spread of the virus, not necessarily the severity of disease caused by the virus. Travel and trade bans may be implemented in some cases, although if the disease is already widespread, these may not be considered effective.

Prior to the emergence of the H1N1 virus, the alert level stood at Phase 3 based on the circulation of the H5N1 virus. On April 27, , after the H1N1 flu virus was recognized to be passing from person to person in Mexico, the alert level was raised to Phase 4. Two days later, on April 29, the WHO again increased the alert level, this time to Phase 5, reflecting the sustained transmission of the novel H1N1 virus in the United States.

As H1N1 continued to spread worldwide and infect people in over 70 countries, the WHO raised the alert to Phase 6 — the highest level - on June 11, Over the next few months, H1N1 spread to more than countries and territories worldwide. Influenza naturally infects wild birds all around the world, although they usually do not become ill. The virus is very contagious, however, and it can become a problem when the virus is transmitted to domesticated birds, such as chickens, ducks, or turkeys, because domesticated poultry can succumb to illness and death from influenza.

Humans generally do not become infected with avian flu. That is why news of humans contracting avian influenza during an outbreak of bird flu in poultry in in Hong Kong was alarming. It indicated that the virus had changed to allow it to directly infect humans. The virus that caused this particular outbreak is influenza A subtype H5N1.

Since , H5N1 infections in birds have spread, initially throughout Asia. Then as birds traveled along their migratory routes, H5N1 dispersed to Russia and Europe, and later to countries in the Middle East and on the African continent. Most human cases of H5N1 influenza have been traced to direct contact with infected poultry, but there have been a few cases of person-to-person transmission, particularly in clusters where multiple family members became infected.

One reason why avian H5N1 is not readily transmissible among people has to do with the hemagglutinin, or HA, protein of the virus that determines which cell type the virus can enter. As with other viruses, the influenza virus must attach to specific proteins called receptors on the outside of cells in order to gain entry into cells and cause an infection.

Unlike human influenza viruses, which infect cells high in the respiratory tract, the H5N1 HA protein attaches to cells much lower in the respiratory track. The virus is so deep within the respiratory tract that it is not coughed up or sneezed out, and so it does not easily infect other people. If the HA protein of H5N1 were to mutate so that it could infect cells higher in the respiratory tract, then it would more likely be able to pass from person to person.

As of July , there have been some laboratory-confirmed cases of H5N1 infections in humans, in 16 different countries, and close to deaths. The countries with the overall highest case numbers are Egypt, where almost all cases in have occurred, followed by Indonesia and Vietnam.

H5N1 continues to circulate in poultry, and small and sporadic clusters of human infections are still occurring. However, H5N1 currently does not transmit easily between people, so the risk of a large outbreak is low at this time. Highly pathogenic H5 avian virus infections were first reported in birds in the United States in December Over approximately the next six months, more than findings of infection with H5N2, H5N8, and H5N1 viruses were confirmed, mostly in poultry including backyard and commercial flocks.

More than 40 million birds in 20 states were either infected or exposed. No human infections by these H5 viruses have been reported in the United States, but their presence in birds makes it more likely than human H5 infections could occur in the United States.

Individuals having close contact with live infected poultry or surfaces contaminated with the avian influenza viruses are at highest risk of infection in places where the viruses circulate. There have been no reports of infection occurring from eating properly cooked poultry. In addition to the H5 viral subtypes, other avian influenza strains have occasionally infected humans in recent years.

These include the H7N2 strain which infected two individuals in the eastern United States in and , and the H9N2 strain which has caused illness in several people in Asia in and In March of , a new subtype of avian influenza was found to infect humans. Influenza A H7N9 had previously been detected in birds, but this particular variant had never been seen before in humans or animals.

The initial wave of H7N9 infections occurred in the spring of in China, followed by a larger, second wave in the first half of in China and a few neighboring countries. As of February , approximately cases and deaths have been reported to the WHO, mostly in China. People in the majority of cases had exposure to infected poultry or contaminated environments.

The H7N9 virus causes a severe respiratory illness in most infected people, but it currently does not appear to spread easily from person to person. Swine influenza, or swine flu, is a very contagious respiratory disease of pigs. Although pigs become ill, they generally do not die from swine flu viruses. In April of , an influenza virus originating in swine was discovered to be capable of infecting humans and spreading from person to person.

The new virus is named influenza A H1N1 , although it is commonly referred to as swine flu. Although it is called swine flu, the new H1N1 virus is transmitted from person to person, and not through contact with pigs or pork products. The new H1N1 virus is made up of a novel combination of segments from four different influenza virus strains - a Eurasian swine virus, a North American swine virus, and avian and human influenza virus segments. Reassortment of segments from these different viruses produced a unique virus that had not been seen before by the human population.

When novel viruses like this emerge, natural immunity is usually limited or nonexistent in humans. The H1N1 influenza virus outbreak originated in Mexico in early , and then spread rapidly throughout North America. Within a few weeks, the novel swine-origin H1N1 virus extended its reach around the globe. In June , as a result of the global spread of the H1N1 virus, the WHO issued its first pandemic declaration of the 21st century - the first since the flu pandemic of The pandemic declaration acknowledged the inability to contain the virus and recognized its inevitable further spread within affected countries and into new countries.

The new H1N1 virus became the dominant influenza strain in most parts of the world, including the United States. Like other influenza pandemics, the H1N1 outbreak occurred in waves. The first wave took place in the spring of , with a second wave commencing in late August as children and college students returned to classes.

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So if you worried at all about your kids during the pandemic, you should make sure they get the flu shot. You should get it too, because the flu kills thousands of adults aged each year an estimated 2, during the flu season and sends tens of thousands to the hospital 66, in As a reminder, vaccines work by giving your body a chance to fight off an altered version of a virus or bacteria, so that if and when it encounters the live virus in the wild, it already knows how to react, and you never get sick.

This combination is then formulated for a shot or spray to make it in time for the flu season. For those science-is-fucking-awesome types out there, this is indeed awesome. Influenza strains constantly mutate, but scientists get one shot at the annual vaccine, making their best guess some 30 weeks in advance to get the flu shot out to the public. When is the best time to get vaccinated? Adults should wait until September or October because protection might wear off by the heavy-hitting months later in the season.

You should definitely be up-to-date by the end of October, though later is better than never. Every year, vaccine developers take virus samples from labs across the world and mix and match them.

The four viruses in the vaccine are somewhat different for the three different types of flu vaccines, which are egg-based the usual vaccine type , recombinant, and egg-free. Those viruses are…. That means a flu strain akin to the one seen in the pandemic that was created in in a lab in Victoria is replacing the strain created in in the Maonan district of Guangdong.

The second component is a variant of the H1N1 swine flu. H3N2 was first found in pigs in , then in humans in The biggest human outbreak was in with some reported cases. Influenza B viruses tend to be the non-pandemic variety because they spread primarily among humans alone. The Influenza B viruses in the flu vaccine are the same as those used during the previous flu season in the Northern Hemisphere. All three types of flu vaccines include these virus lineages.

Beyond the three to four viral components, a number of additives and preservatives are required to make vaccines effective — and to keep them from going bad.

These ingredients , sometimes covered as trade secrets by drug companies in less public drugs, have led to many a conspiracy theory that anti-vaxxers would have you latch onto. To receive weekly email updates about Seasonal Flu, enter your email address:.

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