For example, all personnel must wear a powered air purifying respirator PAPR , double gloves, scrubs, shoe covers and a surgical gown. They also must shower before exiting the laboratory. In addition, all work with the virus or animals must be conducted within a certified Class II biosafety cabinet BSC , and airflow within the laboratory is directionally controlled and filtered so that it cannot accidentally exit the laboratory.
For the reconstruction of the virus, additional rules were created to govern the experiments to be conducted. For example, to prevent mix-ups and cross-contamination, work on the virus could not take place alongside work on other influenza viruses.
That person was trained microbiologist Dr. Julie Gerberding. Tumpey was formerly a U. He officially transferred employment to CDC for the purpose of studying human health implications of influenza viruses, including the pandemic virus. The virus was extremely virulent. Image a shows mouse lung tissue infected with a human seasonal H1N1 flu virus. Image c shows the impact of the virus in mouse lung tissue. The virus replicates quickly and causes severe disease in the lung tissues of mice.
In , the virus caused severe disease in the lungs of people infected, as well. Photo credit: CDC, Science. To reduce risk to colleagues and the public, he was required to work on the virus alone and only after hours when fellow colleagues had exited the laboratories for the day and gone home.
A biometric fingerprint scan was required for access into the BSL-3E laboratory, and the virus storage freezers were only accessible via an iris scan of his eyes. Tumpey was required to take a prescribed prophylactic preventative daily dose of the influenza antiviral drug, oseltamivir, as an additional safety precaution to prevent him from becoming infected.
Should he become infected, he was informed that he would be placed in quarantine and denied contact with the outside world. He understood and accepted this responsibility and its consequences.
Using reverse genetics, Dr. Tumpey took the plasmids created by Dr. The plasmids then instructed the cells to reconstruct the RNA of the complete virus. For multiple weeks in July , colleagues and collaborators asked Dr. Tumpey if he had the virus and if it had appeared in cell-culture yet.
On the day the virus appeared in his cell-culture, Dr. Tumpey knew history had been made, and in fact, a historic virus had been brought back from extinction. Tumpey had become the first man to reconstruct the complete virus. The next step was to study it and unlock its deadly secrets.
Laboratory studies on the reconstructed virus began in August The mice were infected with the virus, and measures of morbidity i. For comparison, other mice were infected with different influenza viruses that were designed via reverse genetics to have varying combinations of genes from the virus and contemporary human seasonal influenza A H1N1 viruses. The fully reconstructed virus was striking in terms of its ability to quickly replicate, i.
For example, four days after infection, the amount of virus found in the lung tissue of infected mice was 39, times higher than that produced by one of the comparison recombinant flu viruses. Furthermore, the virus was highly lethal in the mice. The virus was at least times more lethal than one of the other recombinant viruses tested. Other experiments were conducted to determine if infection with the virus could spread to other vital organs of mice — such as the brain, heart, liver and spleen.
Laboratory testing did not detect virus in these organs, suggesting that the virus did not cause systemic infection in its victims. However, one well-documented effect of the virus was rapid and severe lung damage. In , victims of the pandemic virus experienced fluid-filled lungs, as well as severe pneumonia and lung tissue inflammation. The impact of the virus on lung tissue was also studied using a human lung cell line known as Calu-3 cells.
The amount of flu virus was measured in the cells at 12, 16 and 24 hours post infection and these results were compared to those produced by recombinant viruses with a combination of genes from the virus mixed with genes from contemporary human seasonal flu viruses. Similar to the experiments involving mice, the virus quickly multiplied and spread within the human lung cells. So much so, that the virus produced as much as 50 times the amount of virus in human lung cells as one of the comparison viruses.
Another set of experiments was conducted to better understand the possible avian origins of the virus. The earlier sequencing efforts led by Dr. Researchers were interested to know whether the virus would be lethal to fertilized chicken eggs, i.
To find an answer, day old fertilized chicken eggs were inoculated with the virus. The virus proved lethal for the chicken egg embryos, similar to the effects caused by contemporary H1N1 bird flu viruses.
Furthermore, the recombinant flu viruses that Dr. Tumpey created containing two, five or seven genes of the virus also did not hurt chicken embryos. The work conducted by Dr. Tumpey and his CDC colleagues provided new information about the properties that contributed to the virulence of the virus. Tumpey determined that the HA and PB1 virus genes of the virus played particularly important roles in its infectiousness and severity. In that way, the virus was special — a uniquely deadly product of nature, evolution and the intermingling of people and animals.
Crowded conditions and the movement of troops during World War I likely contributed to the spread of the virus around the world. Photo credit: www. Since , the world has experienced three additional pandemics, in , , and most recently in These subsequent pandemics were less severe and caused considerably lower mortality rates than the pandemic.
Many experts think so. One virus in particular has garnered international attention and concern: the avian influenza A H7N9 virus from China. However, it has not gained the capability to spread quickly and efficiently between people. If it did, experts believe it could result in a pandemic with severity comparable to the pandemic. So far, it has shown only limited ability to spread between people.
Most human infections with this virus have result from exposure to birds. When considering the potential for a modern era high severity pandemic, it is important; however, to reflect on the considerable medical, scientific and societal advancements that have occurred since , while recognizing that there are a number of ways that global preparations for the next pandemic still warrant improvement.
Besides the properties of the virus itself, many additional factors contributed to the virulence of the pandemic. In , the world was still engaged in World War I. Movement and mobilization of troops placed large numbers of people in close contact and living spaces were overcrowded. In addition, medical technology and countermeasures at the time were limited or non-existent. No diagnostic tests existed at the time that could test for influenza infection.
Influenza vaccines did not exist at the time, and even antibiotics had not been developed yet. For example, penicillin was not discovered until Likewise, no flu antiviral drugs were available. Critical care measures, such as intensive care support and mechanical ventilation also were not available in In terms of national, state and local pandemic planning, no coordinated pandemic plans existed in Some cities managed to implement community mitigation measures, such as closing schools, banning public gatherings, and issuing isolation or quarantine orders, but the federal government had no centralized role in helping to plan or initiate these interventions during the pandemic.
Today, considerable advancements have been made in the areas of health technology, disease surveillance, medical care, medicines and drugs, vaccines and pandemic planning. Flu vaccines are now produced and updated yearly, and yearly vaccination is recommended for everyone 6 months of age and older. Antiviral drugs now exist that treat flu illness, and in the event of virus exposure, can be used for prophylaxis prevention , as well. Importantly, many different antibiotics are now available that can be used to treat secondary bacterial infections.
Diagnostic tests for identifying influenza are now available and they are improving over time. Just as important as these advancements in diagnostic tests are the improvements that have been made in laboratory testing capacity both within the United States and globally. King Louis XV was reportedly infected and stated that the disease spread like a foolish little girl, or follette in French.
Only 40 years later, in , another pandemic struck. It arose in China, spread to Russia, and then encompassed Europe and North America over the next year. At its peak, the infection struck 30, people each day in St. Petersburg and affected two-thirds of the population in Rome.
The pandemic of — began in China, and then spread by ships to the Philippines, India and Indonesia, and finally across Russia and into Europe, which experienced two recurrences over the span of the pandemic. Outbreaks appeared in North America from — The Spanish flu, the first known pandemic to involve the H1N1 virus, came in several waves and killed its victims quickly, often within a matter of hours or days.
More U. The 20th century saw two other flu pandemics: the Asian flu caused by H2N2 , which killed 1. Both of these flu strains arose from a genetic reassortment between a human and an avian virus. Compared with previous pandemics, the swine flu was relatively mild, despite killing up to , people worldwide. Shortly after scientists identified the influenza A virus, researchers began work on creating a flu vaccine, with the first clinical trials commencing in the mids.
Given the high death toll of World War I soldiers to the flu, the U. But during these — tests, scientists discovered influenza type B, necessitating a new bivalent vaccine that protects against both H1N1 and the influenza B virus.
After the Asian flu pandemic arose in , a new vaccine protecting against H2N2 was developed. WHO monitored the circulating influenza virus strains in various countries to determine which flu vaccine would be needed in an upcoming season.
Most U. In , the first quadrivalent flu vaccine that protects against an additional influenza B virus was approved for use. Scientists at WHO and its collaborating centers determine which strains to vaccinate against based on how the viruses have mutated in the past year and how they are spreading, with different vaccines needed for the Northern and Southern hemisphere. But given the uncertainties involved in these estimates, vaccine effectiveness can vary widely—the — vaccine was only 10 percent effective in the United States, while the vaccine was 60 percent effective, according to the CDC.
The — flu vaccine was 29 percent effective against Influenza A and B and 44 percent effective in preventing influenza A H1N1 viruses in the United States. Lina B. Springer, Berlin, Heidelberg. Potter, C. Sophie Valtat et al. Flu VE Data for Lone Simonsen et al. Barberis, I. Paules et al. Finds; NYTimes.
But if you see something that doesn't look right, click here to contact us! Subscribe for fascinating stories connecting the past to the present. Human influenza A and B viruses are the most common. These are the bugs that cause the seasonal flu epidemics quite predictably each winter in the United States and around the world.
Most flu vaccines protect against these two types. Almost everyone has heard of the avian flu and the swine flu, both Type A strains of the influenza viruses. Unlike Type B, Type A viruses are further divided into subtypes based on two little protein spikes on the surface of the virus that help it to invade cells: hemagglutin H and neuraminidase N.
These influenza strains can be contracted from human contact with infected animals—birds Avian flu and pigs Swine flu. Avian flu viruses are not currently known to be transmitted easily from human to human. For swine flu, things have recently changed. In the past only people with direct contact with pigs could become infected with swine flu, but the outbreak of the current swine flu virus was caused by a strain that was a mix of genes from swine, bird and human flu viruses, and was easily transmitted from person to person in respiratory droplets.
Influenza B can only be found in humans and as recently discovered harbor seals. Previously it was thought that influenza A causes more severe disease than influenza B because more hospitalized people were associated with influenza A. However, a study of adults with influenza A and influenza B showed similar rates of illness and death for both types. Furthermore, influenza B was shown to be associated with a higher risk of mortality than influenza A in a Canadian study for children of 16 years old or younger.
Influenza C infections, which can infect pigs, usually cause only minor symptoms though it can be more problematic in children, the elderly, and those with other underlying health issues. Unlike A and B, Type C is not believed to create flu epidemics. Influenza D viruses are not known to cause illness in humans. Pigs and cattle though? While Influenza D can be traced back to , and may have been around for a hundred years or more, it was only recently isolated in a diseased pig in Oklahoma in Since then it has been detected worldwide in cows and pigs.
While no one specific day is used to mark the beginning of this season, in the United States it generally is active from October to March, though, depending upon the number of cases, it can reach even into May. In short, it can be flu season for a good chunk of the year.
0コメント