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Template:2009 swine flu outbreak table

The 2009 outbreak of Influenza A virus subtype H1N1 is an epidemic of a new strain of influenza virus identified in April 2009, commonly referred to as "Swine flu." It is thought to be a mutation ("reassortment") of four known strains of influenza A virus subtype H1N1: one endemic in humans, one endemic in birds, and two endemic in pigs (swine). The source of the outbreak in humans is still unknown, but cases were first discovered in the U.S. and soon after in Mexico, which had a surge of cases, many of them fatal. As a result, the U.N.'s World Health Organization (WHO), along with the U.S. Centers for Disease Control and Prevention (CDC), expressed concern that this could become a worldwide flu pandemic, with WHO raising its alert level to "Phase 5" out of the six maximum, indicating that a pandemic was "imminent."

The H1N1 flu mainly spreads in the same way that regular "seasonal influenza" spreads, which is through the air from coughs and sneezes or touching those infected. It cannot be transmitted from eating cooked pork and there are no confirmed cases of anyone becoming infected with this new strain by being in contact with pigs. According to the CDC, it is not yet clear how serious this new virus actually is compared with other influenza viruses. What is known, they state, is that because this is a new virus, most people will not have immunity to it, and illness may eventually become more severe and widespread in different population groups as a result.

As yet there is no vaccine available to prevent infection although companies are in the planning stages for having one available later this year. But there is concern that the virus could mutate again over the coming months, leading to a new and potentially more dangerous flu outbreak later in the year, and a vaccine that will be less effective in preventing its spread.

According to the CDC, the fact that the flu's infection activity can now be monitored more closely may partly explain why more flu cases than normal are being recorded in the United States and other countries. About half of all influenza viruses being detected so far are this new H1N1 virus, and there is mounting evidence that the symptoms are so far milder than health officials feared, as "experts acknowledge is no worse than seasonal influenza for now."

Historical context

Annual influenza epidemics are estimated to affect 5–15% of the global population, resulting in severe illness in 3–5 million patients and causing 250,000–500,000 deaths worldwide. In industrialized countries severe illness and deaths occur mainly in the high-risk populations of infants, the elderly, and chronically ill patients.

In addition to these annual epidemics, the influenza A virus caused three major global pandemics during the 20th century: the Spanish flu in 1918, Asian flu in 1957 and Hong Kong flu in 1968–69. These pandemics were caused by an Influenza A virus that had undergone major genetic changes, due to which the population did not possess significant immunity to the virus. The overall effects of these pandemics are summarized in the table below.

The influenza virus has also caused several pandemic threats over the past century, including the pseudo-pandemic of 1947, the 1976 swine flu outbreak and the 1977 Russian flu, all caused by the H1N1 subtype. The world has been at an increased level of alert since the SARS epidemic in Southeast Asia (caused by the SARS coronavirus). The level of preparedness was further increased and sustained with the advent of the H5N1 bird flu outbreaks because of H5N1's high fatality rate, although the strains currently prevalent have limited human-to-human transmission (anthroponotic) capability, or epidemicity.

People who contracted flu prior to 1957 may have some immunity. A May 20th New York Times article stated: “Tests on blood serum from older people showed that they had antibodies that attacked the new virus, Dr. Daniel Jernigan, chief flu epidemiologist at the Centers for Disease Control and Prevention, said in a telephone news conference. That does not mean that everyone over 52 is immune, since some Americans and Mexicans older than that have died of the new flu.”

Geographical outbreaks

Initial outbreaks in U.S. and Mexico

U.S.

Both the place and the species in which the virus originated are unknown. Analysis has suggested that the H1N1 strain responsible for the current outbreak first evolved around September 2008 and circulated in the human population for several months before the first cases were detected. The new strain was first diagnosed in two children by the CDC, first on April 14 in San Diego County, California and a few days later in nearby Imperial County, California. Neither child had been in contact with pigs.

Mexico

The outbreak was first detected in Mexico City, where surveillance began picking up a surge in cases of influenza-like illness starting March 18th. The surge was initially assumed by Mexican authorities to be "late-season flu" outbreak and not a new virus strain. After samples were sent to the CDC in mid-April, however, the Mexican cases were confirmed by the CDC and the World Health Organization to be a new strain of H1N1. Although Mexican news media had speculated that the outbreak may have started at a pig plant that engaged in intensive farming practices, to date, no pigs in Mexico have tested positive for the virus and investigators have found no swine influenza at any of the pig farms.

Influenza (flu)
Types Avian A/H5N1 subtype Canine Equine Swine A/H1N1 subtype
Vaccines 2009 pandemic Pandemrix Live attenuated Seasonal flu vaccine brands
Treatment Amantadine Baloxavir marboxil Laninamivir Oseltamivir Peramivir Rimantadine Umifenovir Zanamivir
Pandemics 1889-1890 Russian flu 1918 Spanish flu 1957-1958 Asian flu 1968 Hong Kong flu 1977 Russian flu 2009 swine flu
Outbreaks 1976 swine flu 2006 H5N1 India 2007 Australian equine 2007 Bernard Matthews H5N1 2008 West Bengal 2015 United States H5N2 outbreak 2020–2022 H5N8 outbreak
See also Flu season Influenza evolution Influenza research Influenza-like illness Vaccine reformulations
v t e

Current situation in selected countries

Mexico

A May 21st Associated Press article stated: 'City Health Secretary Armando Ahued said nobody has been hospitalized with respiratory infections in the last three days, and no swine flu cases have been confirmed since May 14. "We are seeing a 96.1 percent drop in cases, and that's why we are dropping the alert level to green today," Ahued said.'

United States

The outbreak has spread to 47 states and the District of Columbia; however, with over 5000 confirmed or probable cases as of May 20th, only 9 deaths have been confirmed. In a press briefing on May 20, Dr. Daniel Jernigan of the CDC stated that of the 247 individuals hospitalized because of the swine flu, over 70% had underlying chronic medical conditions--including pregnancy, asthma, and heart disease.

New York City

On May 21, the New York State Department of Health stated that of the 333 laboratory-confirmed cases in the state, 227 were in New York City. See Also: Local Links for NYC

Houston

A May 21st article in the Houston Chronicle states: “Houston's largest concentration of swine flu cases has grown by one to 25 at Travis Elementary, although the city's health department said the latest case actually was part of the cluster of illnesses that caused the school to shut down last week. . . . As of Wednesday there had been 121 confirmed cases of the disease in the Houston area, according to the city."

Britain

May 21st AP article: "British health authorities have confirmed three new cases of swine flu, bringing the country's total to 112. The Health Protection Agency said Thursday May 21 2009 that the new cases are all children living in the West Midlands. The children had all recently returned from an affected area in the U.S."

Japan

A May 21st article from Time/CNN stated: “The Japanese government on Wednesday confirmed the first two cases of the disease in Tokyo, the world's most populous metropolitan area. Meanwhile, the number of Japanese who have contracted the new flu has more than doubled since May 18 from 130 to 279, a rate of increase that is "without a doubt" the highest in Asia, says Peter Cordingley, regional spokesman for the World Health Organization.” According to the Asahi Shinbun, the worst affected regions are Hyogo and Osaka prefectures.

Southern hemisphere

The outbreak comes at the beginning of the flu season for the Southern Hemisphere, including Australia, Oceania, southern Africa, and most of South America. July is usually the height of flu season in this part of the world.In a May 18th article, CDC’s Dr. Richard Besser was quoted as saying in reference to the Southern Hemisphere: “We’ll be looking at the virus to see has mutated into something more severe.”

2009 H1N1 influenza strain

The virus is a new strain of influenza, from which human populations have not been vaccinated or naturally immunized. The CDC, after examining virus samples from suspected cases in Mexico, matched the strain with those from cases in Texas and California, and found no known linkages to animals or one another. They determined that the strain contained genes from four different flu viruses: North American swine influenza; North American avian influenza; human influenza; and swine influenza virus typically found in Asia and Europe. Further analysis showed that several of the proteins of the virus are most similar to strains that cause mild symptoms in humans, leading some to suggest that the virus is unlikely to cause severe symptoms for most people.

However, many experts are concerned that the new virus strain could mutate over the coming months. Guan Yi, a leading virologist from the University of Hong Kong, for instance, has described the new H1N1 influenza virus as "very unstable", meaning it could mix and swap genetic material when exposed to other viruses. During an interview he said "Both H1N1 and H5N1 are unstable so the chances of them exchanging genetic material are higher, whereas a stable (seasonal flu) virus is less likely to take on genetic material." The H5N1 virus, commonly called "avian influenza," has a mortality rate of between 60% to 70% verses only 0.1% for seasonal influenza." Experts therefore worry about the emergence of a hybrid of the more dangerous H5N1 with the more transmissible H1N1, especially since H5N1 is now believed to be endemic in countries like China, Indonesia, Vietnam and Egypt.

Infection potential

The new H1N1 strain infects by human-to-human transmission. Investigations of infected patients indicated no direct contact with swine, such as at a farm or agricultural fair. The strain was later confirmed to have been transmitted between humans. Epidemiological estimates place the basic reproduction number (R₀) at 1.4 to 1.6 persons infected per case, while genetic analysis predicts R₀ of 1.2; thus the transmissibility of the virus is substantially higher than that of the seasonal flu and comparable to the lower end R₀ estimates for previous pandemics (1.4-2 for 1918, 1957 and 1968) The generation time (the time until an infected person begins infecting others) was estimated to be 1.3-2.71 days, which is somewhat shorter than estimates for previous pandemics.

Virulence

Preliminary findings by the WHO Rapid Pandemic Assessment Collaboration estimate the case-fatality rate (CFR) in a range from 0.3% to 1.4%, with 0.4% the most likely value. Study of the early community-wide outbreak in La Gloria found that 61% of children and 29% of adults were infected, and the lack of fatalities in that case predict that it is 95% likely that the case-fatality rate is below 0.6%. This 0.3%-0.6% range of estimated CFR would correspond to a high category 2 or low category 3 pandemic on the Pandemic Severity Index. This CFR is roughly comparable to that of the 1957 Asian flu, a category 2 pandemic that killed approximately 1 to 4 million people. If 30% of the current world population ended up being infected with H1N1, which is a fairly typical proportion for a flu pandemic, then a CFR of 0.3%-0.6% would result in around 6 to 12 million deaths.

Most of the fatalities to date have been in Mexico where, according to the New York Times, the deaths from the illness have primarily been young, healthy adults. Most influenza strains produce the worst symptoms in young children, the elderly, and others with weaker immune systems. However, the CDC has indicated that symptoms reported from this strain so far are similar to those of normal seasonal flu. While some media outlets have speculated that this virus could cause a cytokine storm in patients, there is presently no evidence for this hypothesis, with the CDC stating that there is "insufficient information to date about clinical complications of this variant of swine-origin influenza A (H1N1) virus infection." A second flu strain, a variant of the seasonal H3N2 virus, has been observed by Canadian researchers and tentatively linked to a case returning from Mexico in mid-March, raising the possibility that this strain may account for some of the unusual patterns of illness observed in Mexico.

International cases and media responses

The initial outbreak received a week of near-constant media attention with the story spreading through news networks. And epidemiologists cautioned that the number of cases reported in the early days of an outbreak can be very inaccurate and deceptive due to several causes, including selection bias, media bias, and incorrect reporting by governments. This could also be due to authorities in different countries looking at different population groups, many poor, which may in part explain higher mortality rates in countries such as Mexico. Furthermore, countries with poor health care systems and older laboratory facilities may take longer to identify or report cases.

The new strain has spread widely beyond Mexico and the U.S., with confirmed cases in forty-one countries and suspected cases in fifty. Many countries have advised their inhabitants not to travel to infected areas. Areas including Australia, Hong Kong, Iceland, India, Indonesia, Malaysia, Philippines, Singapore, South Korea and Thailand are monitoring visitors returning from flu-affected areas to identify people with fever and respiratory symptoms. Mexico closed its schools, universities, and public places for a week to control its spread.

Most cases outside North America are recent travellers to Mexico or the US. Intra-national infections have been reported only from Mexico, the USA, Canada, the UK (37), Spain (22), Germany (2), Italy (1), and Belgium (2)

On May 15th, the CDC lifted its swine flue travel advisories for travel to Mexico and the U.S. State Department followed suit. In lifting its warning, the CDC said, "There is evidence that the Mexican outbreak is slowing down in many cities though not all.” It also said that the “risk of severe disease” from the H1N1 virus "now appears to be less than originally thought."

Government actions against pigs and pork

Although the FAO, WHO, and OIE have reaffirmed that the H1N1 virus is not known to be transmissible from eating cooked pork or pork products, countries including Serbia, China, and Russia, have nevertheless banned the import and sale of pork products "as a precaution against swine flu". And in late April, the Egyptian Government had begun to kill all 300,000 pigs in Egypt, despite a lack of evidence that the pigs had, or were even suspected of having, the virus. This led to clashes between pig owners and the police in Cairo. Egypt's 80-million population consists mainly of Muslims, whose religion forbids them from eating pork, but also has an estimated six to ten percent of its population being native Christians (Copts), who eat pork as part of their diet.

On May 10, in Alberta, Canada, officials quarantined 500 pigs at a pig farm which had caught the H1N1 virus, with evidence that some of the animals may have caught the virus from a person who had recently visited Mexico. The Canadian Food Inspection Agency said it's unlikely an Alberta farm's swine-flu-stricken hogs will be destroyed, however, but says it will take at least three to four weeks to decide what to do with the herd.

Pandemic potential

WHO and CDC officials remain concerned that this outbreak may yet become a pandemic. While tracking the progression of the H1N1 epidemic, public health organizations announced a Pandemic Alert Level, describing the degree to which the virus has been able to spread among humans, and a Pandemic Severity Index, which predicts the number of fatalities if 30% of the human population were infected. The criteria for these anouncements included the novelty, epidemicity and virulence of the strain.

By the end of April, some scientists believed that this strain was unlikely to cause as many fatalities as earlier pandemics, and may not even be as damaging as a typical flu season. On the other hand, the figures from the preliminary findings by the WHO Rapid Pandemic Assessment Collaboration suggest that the lethality of H1N1 may be roughly three to six times that of typical seasonal flu.

However, predicting the size and severity of influenza outbreaks is a very inexact science. In 1976 the U.S. government incorrectly predicted a swine flu pandemic that never materialized. ;That said, WHO officials observed that because there are "human cases associated with an animal influenza virus, and because of the geographical spread of multiple community outbreaks, plus the somewhat unusual age groups affected, these events are of high concern".

Symptoms and expected severity

The CDC has stated that the symptoms of this new H1N1 flu virus are similar to the symptoms of seasonal flu and can include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, or fatigue. A significant number of infected people have also reported diarrhea and vomiting. People at higher risk of serious complications include people age 65 years and older, children younger than 5 years old, pregnant women, people of any age with chronic medical conditions (such as asthma, diabetes, or heart disease), and people who are immunosuppressed (e.g., taking immunosuppressive medications or infected with HIV). Signs of the flu are usually mild and will not require medical evaluation in a clinic.

Avoid contact with others

If you show symptoms for the flu, expect them to last a week or longer. You should stay home and avoid contact with other persons, except to seek medical care, if necessary. If you leave the house to seek medical care, you should wear a mask or cover your coughs and sneezes with a tissue. In general you should avoid contact with other people as much as possible to keep from spreading your illness. Remain home from school, work, or social gatherings. Avoid traveling or driving when you feel ill, especially if you have a fever.

The CDC believes that this virus has the same properties in terms of spread as seasonal flu viruses and persons may be contagious from one day before they develop symptoms to seven days after they get ill. Children, especially younger children, might potentially be contagious for longer periods.

Symptoms requiring medical care

People suffering from more severe symptoms should contact their doctor or hospital for advice. The following additional symptoms might require urgent medical care:

Children

Fast breathing or trouble breathing; bluish or gray skin color; not drinking enough fluids; severe or persistent vomiting; not waking up or not interacting; irritable and not wanting to be held; getting flu-like symptoms that improve but then return with fever and worse cough.

Adults

Difficulty breathing or shortness of breath; pain or pressure in the chest or abdomen; sudden dizziness; confusion; severe or persistent vomiting; flu-like symptoms improve but then return with fever and worse cough.

About half of all influenza viruses being detected so far are the new H1N1 virus, and there is mounting evidence that the symptoms are so far milder than health officials feared. As of May 21st, for instance, despite 201 confirmed cases in New York City, most have been mild and there has been only one confirmed death from the virus. Similarly, Japan has reported 279, mostly mild flu cases, and no deaths. And in Mexico, where the outbreak began last month, Mexico City officials lowered their swine flu alert level as no new cases have been reported for a week. World Health Organization Director General Margaret Chan has stopped short of declaring a "pandemic" by moving to phase six because of recent doubts fostered by its mild symptoms to date.

Prevention and treatment

Personal hygiene

Recommendations to prevent infection by the virus consist of the standard personal precautions against influenza. This includes frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public. The CDC advises not touching the mouth, nose or eyes, as these are primary modes of transmission. When coughing, they recommend coughing into a tissue and disposing of the tissue, then immediately washing the hands. Chance of transmission is also reduced by disinfecting household surfaces, which can be done effectively with a diluted chlorine bleach solution.

Home treatment remedies

The Mayo Clinic has suggested a number of measures to help ease symptoms:

• Drink plenty of liquids, especially water, juice and warm soups to prevent dehydration. Drink enough so that your urine is clear or pale yellow.
• Rest and sleep to help your immune system fight the infection.
• Chicken soup: "It's not just good for your soul — it really can help relieve flu symptoms by breaking up congestion."
• Over-the-counter pain relievers, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others) cautiously, as needed. Note that while pain relievers may make you more comfortable by relieving symptoms, they won't make the flu go away any faster and may have side effects. For instance, Ibuprofen may cause stomach pain, bleeding and ulcers if taken for a long period or in higher than recommended doses. Acetaminophen can be toxic to your liver. Mayo suggests you talk to your doctor before giving acetaminophen to children, and not to give aspirin to children or teens because of the risk of Reye's syndrome, a rare but potentially fatal disease.

Fever relief

According to Medline Encyclopedia, aspirin is very effective for treating fever in adults but is not recommended for children unless directed by a doctor. Other medications, such as acetaminophen and ibuprofen will help reduce fever in children and adults, and acetaminophen can be taken every 4 - 6 hours. It works by turning down the brain's thermostat. Ibuprofen can be taken every 6 - 8 hours. Like aspirin, it helps fight inflammation at the source of the fever. Sometimes doctors advise you to use both types of medicine, although ibuprofen is not approved for use in children younger than 6 months old.

According to the CDC, it is expected that most people will recover without needing medical care. However, they recommend that anyone with severe illness or at high risk of flu complications, to contact their health care provider or seek medical care. The health care provider will determine whether flu testing or treatment is needed. The CDC also notes that should the flu become widespread, there will be little need to continue testing people, and they may decide not to test for the flu virus.

Transmission

Sneezes or coughs

There is so far little data available on the risk of airborne transmission of this particular virus. Mexican authorities are distributing surgical masks to the general public. The UK Health Protection Agency considers facial masks unnecessary for the general public. Many authorities recommend the use of respirators by health-care workers in the vicinity of pandemic flu patients, in particular during aerosol generating procedures (e.g. intubation, chest physiotherapy, bronchoscopy).

Touching

Infection can be caused by touching something with flu viruses on it and then touching your mouth or nose. The virus can have a lifetime of up to two hours outside the body, so can be transmitted by handling door knobs, glasses, kitchen utensils, or touching the skin of an infected person and then touching your own mouth.

Safe to eat pork

The leading international health agencies have stressed that the "influenza viruses are not known to be transmissible to people through eating processed pork or other food products derived from pigs."

Antiviral drugs

According to the CDC, antiviral drugs can be given to treat those who become severely ill, however these antiviral drugs are prescription medicines (pills, liquid or an inhaler) and act against influenza viruses, including H1N1 flu virus. There are two influenza antiviral medications that are recommended for use against H1N1 flu. The drugs that are used for treating H1N1 flu are called oseltamivir (trade name Tamiflu ®) and zanamivir (Relenza ®). The CDC notes that as the H1N1 flu spreads, these antiviral drugs may become in short supply. Therefore, the drugs will be given first to those people who have been hospitalized or are at high risk of complications. The drugs work best if given within 2 days of becoming ill, but may be given later if illness is severe or for those at a high risk for complications.

When buying these medications, some agencies such as the MHRA in the UK have recommended not using online sources, as the WHO estimates that half the drugs sold by online pharmacies without a physical address are counterfeit. Medical experts are also concerned that people "racing to grab up antiviral drugs just to feel safe" may eventually lead to the virus developing drug resistance. Partly as a result, experts suggest the medications should be reserved for only the very ill or people with severe immune deficiencies.

In H3N2 strains, Tamiflu treatment leads to resistance in 0.4% of adult cases and 5.5% of children. Resistant strains are usually less transmissible; nonetheless resistant human H1N1 viruses became widely established in previous flu seasons. Marie-Paule Kiely, WHO vaccine research director, has said that it is "almost a given" that the new strain would undergo reassortment with resistant seasonal flu viruses and acquire resistance, but it is not yet known at what level resistance will appear. Simulations suggest that if physicians choose a second effective antiviral such as zanamivir (Relenza) as first-line treatment in even a few percent of cases, this can greatly delay the spread of resistant strains. Even a drug such as amantadine (Symmetrel) for which resistance frequently emerges may be useful in combination therapy.

Vaccines

Influenza vaccines are typically developed to cope with seasonal flu to minimize infection rates, yet it still kills around 500,000 people a year around the world. Currently, most of the world's flu vaccines use an injection of "killed virus," a vaccine method made famous by Jonas Salk when he developed the first vaccine against the polio virus in 1955. As The Economist magazine summarizes the problem today, however, "if a global pandemic is declared and manufacturers are asked to produce a vaccine for H1N1, they are unlikely to be able to respond quickly enough." Furthermore, vaccine producers can produce about a billion doses of any one vaccine each year, so that even if all the capacity was switched to fight the a pandemic flu, as opposed to a seasonal flu, "there would still be a huge global shortfall." Keiji Fukuda of the WHO said, "There’s much greater vaccine capacity than there was a few years ago, but there is not enough vaccine capacity to instantly make vaccines for the entire world’s population for influenza." The seasonal flu vaccine is not believed to protect against the new strain, therefore any existing stock would not be useful.

There is also concern that should a second, deadlier wave of a new H1N1 strain reappear during the Northern autumn of 2009, producing pandemic vaccines now as a precaution may turn out to be a huge waste of resources with serious results, as the vaccine may not be as effective, and there would also be a shortage of seasonal flu vaccine available. William Schaffner, an infectious disease researcher at Vanderbilt University in Tennessee, USA, stated, referring to Northern hemisphere seasons, that "for now, there is no way to tell whether the swine flu will die out this spring, or tarry through the summer and reappear as a stronger, meaner virus in the fall."

The costs of producing a vaccine have also become an issue, with some U.S. lawmakers questioning whether a vaccine is worth the unknown benefits. Representatives Phil Gingrey and Paul Broun, for instance, are not convinced that the U.S. should spend up to $2 billion to produce one, with Gingrey stating "We can’t let all of our spending and our reaction be media-driven in responding to a panic so that we don’t get Katrina-ed. ... It’s important because what we are talking about as we discuss the appropriateness of spending $2 billion to produce a vaccine that may never be used — that is a very important decision that our country has to make."

Moreover, should a pandemic be declared and a vaccine produced, the WHO will attempt to make sure that a substantial amount is available for the benefit of developing countries. Vaccine makers and countries with standing orders, such as the U.S. and a number of European countries, will be asked, according to WHO officials, "to share with developing countries from the moment the first batches are ready if an H1N1 vaccine is made." The global body stated that it wants companies to donate at least 10 percent of their production or offer reduced prices for poor countries that could otherwise be left without vaccines if there is a sudden surge in demand.

Production decisions

After a meeting with the WHO on May 14, 2009, pharmaceutical companies said they were ready to begin making a swine flu vaccine. According to news reports, the WHO's experts will present recommendations to WHO Director-General Margaret Chan, who is expected to issue advice to vaccine manufacturers and the World Health Assembly next week. WHO's Keiji Fukuda told reporters "These are enormously complicated questions, and they are not something that anyone can make in a single meeting." Most flu vaccine companies can only make one vaccine at a time: seasonal flu vaccine or pandemic vaccine. Production takes months and it is impossible to switch halfway through if health officials make a mistake. . . . if the swine flu mutates, scientists aren't sure how effective a vaccine made now from the current strain will remain." Rather than wait on the WHO decision, however, some countries in Europe have decided to go ahead with early vaccine orders.

A May 20th AP article reported: “Manufacturers won't be able to start making the vaccine until mid-July at the earliest, weeks later than previous predictions, according to an expert panel convened by WHO. It will then take months to produce the vaccine in large quantities. The swine flu virus is not growing very fast in laboratories, making it difficult for scientists to get the key ingredient they need for a vaccine, the "seed stock" from the virus, WHO said. . . . In any case, mass producing a pandemic vaccine would be a gamble, as it would take away manufacturing capacity for the seasonal flu vaccine that kills up to 500,000 people each year. Some experts have wondered whether the world really needs a vaccine for an illness that so far appears mild.”

Another option proposed by the CDC is an "earlier rollout of seasonal vaccine," according to the CDCs Dr. Daniel Jernigan. He said the CDC would work with vaccine manufacturers and experts to see if that would be possible and desirable. Flu vaccination usually starts in September in the United States and peaks in November. Some vaccine experts agree it would be better to launch a second round of vaccinations against the new H1N1 strain instead of trying to add it to the seasonal flu vaccine or replacing one of its three components with the new H1N1 virus.

As of early May, only a few more weeks were needed for the WHO and CDC to develop a "seed strain" of the pandemic virus, but producers would then need four to six months before they could create large volumes of vaccine. In a May 14 interview, Doris Bucher, who heads one of three labs worldwide tasked with producing seed virus, said that seed virus production was on target for a May 22 ship date. The seed virus is produced using an H3N2 influenza strain, NYMC X-157, which grows quickly in eggs. This strain is allowed to undergo reassortment with the swine flu strain by injecting both at high concentrations into the allantois of an egg so that single cells are infected by both viruses. The resulting hybrid viruses are then subjected to an artificial selection in which any viruses with H3 or N2 antigens are removed, and the strains growing fastest in eggs are favored. The resulting virus resembles swine flu on the outside and X-157 on the inside and can be rapidly grown to produce vaccine.

Containment

On April 28, WHO's Dr. Keiji Fukuda pointed out that it is too late to contain the swine flu. "Containment is not a feasible operation. Countries should now focus on mitigating the effect of the virus," he said. He therefore did not recommend closing borders or restricting travel, stating that "with the virus being widespread... closing borders or restricting travel really has very little effects in stopping the movement of this virus." However, on April 28, the U.S. CDC began "recommending that people avoid non-essential travel to Mexico." Many other countries confirmed that inbound international passengers will be screened. Typical airport health screening involves asking passengers which countries they have visited and checking whether they feel or appear particularly unwell. Thermographic equipment was put into use at a number of airports to screen passengers. A number of countries also advised against travel to known affected regions while experts have suggested that if those infected stay at home or seek medical care, public meeting places are closed, and anti-flu medications are made widely available, then in simulations the sickness is reduced by nearly two-thirds.

Naming the disease

Scientific name and common name

According to researchers cited by The New York Times, "based on its genetic structure, the new virus is without question a type of swine influenza, derived originally from a strain that lived in pigs". This origin gave rise to the nomenclature "swine flu", largely used by mass media in the first days of the epidemic. Despite this origin, the current strain is now a human-to-human issue, requiring no contact with swine. On April 30 the World Health Organization stated that no pigs in any country had been determined to have the illness, but farmers remain alert due to concerns that infected humans may pass the virus to their herds. On May 2, it was announced that a Canadian farm worker who had traveled to Mexico had transmitted the disease to a herd of pigs, showing that the disease can still move between species.

Debate over name

Some authorities object to calling the flu outbreak "swine flu". U.S. Agriculture Secretary Tom Vilsack expressed concerns that this would lead to the misconception that pork is unsafe for consumption. In the Netherlands, it was originally called "pig flu", but is now called "Mexican flu" by the national health institute and in the media. South Korea and Israel briefly considered calling it the "Mexican virus". Currently, the South Korean press uses "SI", short for "swine influenza". Taiwan suggested the names "H1N1 flu" or "new flu", which most local media now use. The World Organization for Animal Health has proposed the name "North American influenza". The European Commission uses the term "novel flu virus".

The WHO announced they would refer to the new influenza virus as influenza A (H1N1) or "Influenza A (H1N1) virus, human" as opposed to "swine flu", also to avoid suggestions that eating pork products carried a risk of infection.

The outbreak has also been called the "H1N1 influenza", "2009 H1N1 flu", or "swine-origin influenza". However, Seth Borenstein, writing for the Associated Press quoted several experts who objected to any name change at all.

See also

• 1918 flu pandemic
• 1976 swine flu outbreak
• 2009 swine flu outbreak by country
• Hong Kong Flu (1968–1969)
• Bird Flu
• Severe acute respiratory syndrome (SARS)

References

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External links

• Official swine flu advice and latest information from the UK National Health Service
• Template:Dmoz
• Swine influenza, at the World Health Organization
• Pan-American Health Organization (PAHO) Swine Influenza portal
• H1N1 Influenza (Flu) portal at the U.S. Centers for Disease Control (CDC)
• H1N1 Influenza Virus - CDC Workplace (NIOSH)
• Influenza A(H1N1) at the European Centre for Disease Prevention and Control (ECDC)
• International Society for Infectious Diseases PROMED-mail news updates
• U.S. Government swine, avian and pandemic flu portal
• Medical Encyclopedia Medline Plus: Swine Flu
• Swine Flu Outbreak, Influenza Virus Resource Sequences and related resources (GenBank, NCBI)
• BioHealthBase Bioinformatics Resource Center Database of influenza genomic sequences and related information.
• Human/Swine A/H1N1 Influenza Origins and Evolution Analysis of genetic data for the origin and evolution of swine flu virus.
• CIDRAP (Center for Infectious Disease Research & Policy at University of Minnesota) Novel H1N1 Influenza (Swine Flu)
• Influenza Report Medical textbook, 225 pages, PDF, free Download
• BioMed Central Influenza Gateway
• Health Officials Race to Create H1N1 Flu Vaccine, transcript of PBS NewsHour, BETTY ANN BOWSER reporting, May 20, 2009. PHIL HOSBACH of Sanofi Pasteur says: “ . . . normally take about three to four months before it would yield the first doses that we could make available to public health authorities . . . ”
• Swine Flu Trends Worldwide trends for the spread of the 2009 H1N1 Influenza outbreak

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• 2009 swine flu outbreak
• Influenza A virus subtype H1N1
• 2000s medical outbreaks