What is swine flu?

(Note: U.S. researchers are trying to term 2009 swine flu viruses as H1N1 flu viruses as of April 2009.)

Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs and result in nasal secretions, a barking-like cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. Swine flu can last about one to two weeks in pigs that survive. Swine influenza virus was first isolated from pigs in 1930 in the U.S. and has been recognized by pork producers and veterinarians to cause infections in pigs worldwide. In a number of instances, people have developed the swine flu infection when they are closely associated with pigs (for example, farmers, pork processors), and likewise, pig populations have occasionally been infected with the human flu infection. In most instances, the cross-species infections (swine virus to man; human flu virus to pigs) have remained in local areas and have not caused national or worldwide infections in either pigs or humans. Unfortunately, this cross-species situation with influenza viruses has had the potential to change. Investigators think the 2009 swine flu strain, first seen in Mexico, should be termed H1N1 flu since it is mainly found infecting people and exhibits two main surface antigens, H1 (hemagglutinin type 1) and N1 (neuraminidase type1).

Why is swine flu now infecting humans?
Many researchers now consider that two main series of events can lead to swine flu (and also avian or bird flu) becoming a major cause for influenza illness in humans.
First, the influenza viruses (types A, B, C) are enveloped RNA viruses with a segmented genome; this means the viral RNA genetic code is not a single strand of RNA but exists as eight different RNA segments in the influenza viruses. A human (or bird) influenza virus can infect a pig respiratory cell at the same time as a swine influenza virus; some of the replicating RNA strands from the human virus can get mistakenly enclosed inside the enveloped swine influenza virus. For example, one cell could contain eight swine flu and eight human flu RNA segments. The total number of RNA types in one cell would be 16; four swine and four human flu RNA segments could be incorporated into one particle, making a viable eight RNA segmented flu virus from the 16 available segment types. Various combinations of RNA segments can result in a new subtype of virus (known as antigenic shift) that may have the ability to preferentially infect humans but still show characteristics unique to the swine influenza virus (see Figure 1). It is even possible to include RNA strands from birds, swine, and human influenza viruses into one virus if a cell becomes infected with all three types of influenza (for example, two bird flu, three swine flu, and three human flu RNA segments to produce a viable eight-segment new type of flu viral genome). Formation of a new viral type is considered to be antigenic shift; small changes in an individual RNA segment in flu viruses are termed antigenic drift and result in minor changes in the virus. However, these can accumulate over time to produce enough minor changes that cumulatively change the virus' antigenic makeup over time (usually years).Second, pigs can play a unique role as an intermediary host to new flu types because pig respiratory cells can be infected directly with bird, human, and other mammalian flu viruses. Consequently, pig respiratory cells are able to be infected with many types of flu and can function as a "mixing pot" for flu RNA segments (see Figure 1). Bird flu viruses, which usually infect the gastrointestinal cells of many bird species, are shed in bird feces. Pigs can pick these viruses up from the environment and seem to be the major way that bird flu virus RNA segments enter the mammalian flu virus population.

What are the symptoms of swine (H1N1) flu?
Symptoms of swine flu are similar to most influenza infections: fever (100F or greater), cough, nasal secretions, fatigue, and headache, with fatigue being reported in most infected individuals. Some patients also get nausea, vomiting, and diarrhea. In Mexico, many of the patients are young adults, which made some investigators speculate that a strong immune response may cause some collateral tissue damage. Some patients develop severe respiratory symptoms and need respiratory support (such as a ventilator to breathe for the patient). Patients can get pneumonia (bacterial secondary infection) if the viral infection persists, and some can develop seizures. Death often occurs from secondary bacterial infection of the lungs; appropriate antibiotics need to be used in these patients. The usual mortality (death) rate for typical influenza A is about 0.1%, while the 1918 "Spanish flu" epidemic had an estimated mortality rate ranging from 2%-20%. Swine flu in Mexico (as of April 2009) has had about 160 deaths and about 2,500 confirmed cases, which would correspond to a mortality rate of about 6%, but it is far too early to be sure this is the true mortality rate because the data is still being collected and there are new infections being reported in Mexico. By June 2009, the virus had reached 74 different countries on every continent except Antarctica.

How is swine flu (H1N1) diagnosed?
Swine flu is presumptively diagnosed clinically by the patient's history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, nasopharyngeal swab sample) is done to see if the patient is infected with influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for type A and B. If the test is positive for type B, the flu is not likely to be swine flu (H1N1). If it is positive for type A, the person could have a conventional flu strain or swine flu (H1N1). Swine flu (H1N1) is definitively diagnosed by identifying the particular antigens associated with the virus type. In general, this test is done in a specialized laboratory and is not done by many doctors' offices or hospital laboratories. However, doctors' offices are able to send specimens to specialized laboratories if necessary.

What treatment is available for swine (H1N1) flu?
Although the greatest treatment for influenza infections in humans is prevention by vaccination, to date (June 2009), there is no vaccine available for swine (H1N1) flu. Ongoing work by several laboratories is likely to produce a vaccine later this year. Two antiviral agents have been reported to help prevent or reduce the effects of swine flu. They are zanamivir (Relenza) and oseltamivir (Tamiflu), both of which are also used to prevent or reduce influenza A and B symptoms. These drugs should not be used indiscriminately, because viral resistance to them can and has occurred. Also, they are not recommended if the flu symptoms already have been present for 48 hours or more. Severe infections in some patients may require additional supportive measures such as ventilation support and treatment of other infections like pneumonia that can occur in patients with a severe flu infection. The U.S. Centers for Disease Control and Prevention (CDC) has suggested in their interim guidelines that pregnant females can be treated with the two antiviral agents.

What is the history of swine flu?
In 1976, there was an outbreak of swine flu at Fort Dix. This virus is not the same as the 2009 outbreak, but it was similar insofar as it was an influenza A virus that had similarities to the swine flu virus. There was one death at Fort Dix. The government decided to produce a vaccine against this virus, but the vaccine was associated with neurological complications (Guillain-Barré syndrome) and was discontinued. Some individuals speculate that formalin, used to inactivate the virus, may have played a role in the development of this complication in 1976. There is no evidence that anyone who obtained this vaccine would be protected against the 2009 swine flu. One of the reasons it takes a few months to develop a new vaccine is to test the vaccine for safety to avoid the complications seen in the 1976 vaccine. New vaccines against any flu virus type are usually made by growing virus particles in eggs. A serious side effect (allergic reaction such as swelling of the airway) to vaccines can occur in people who are allergic to eggs; these people should not get flu vaccines. Individuals with active infections or diseases of the nervous system are also not recommended to get flu vaccines.

How can swine (H1N1) flu be prevented?
The best way to prevent swine flu would be the same best way to prevent other influenza infections, and that is vaccination. When a safe vaccine is developed (projected to happen in a few months), people should get vaccinated if the disease is still causing infections. The CDC says that a good way to prevent any flu disease is to avoid exposure to the virus; this is done by frequent hand washing, not touching your hands to your face (especially the nose and mouth), and avoiding any close proximity to or touching any person that may have flu symptoms. Since the virus can remain viable and infectious for about 48 hours on many surfaces, good hygiene and cleaning with soap and water or alcohol-based hand disinfectants are also recommended. Some physicians say face masks may help prevent getting airborne flu viruses (for example, from a cough or sneeze), but others think the better use for masks would be on those people who have symptoms and sneeze or cough. The use of Tamiflu or Relenza may help prevent the flu if taken before symptoms develop or reduce symptoms if taken within about 48 hours after symptoms develop. However, taking these drugs is not routinely recommended for prevention because investigators suggest that as occurs with most drugs, flu strains will develop resistance to these medications. Your doctor should be consulted before these drugs are prescribed.
In general, preventive measures to prevent the spread of flu are often undertaken by those people who have symptoms. Symptomatic people should stay at home, avoid crowds, and take off from work or school until the disease improves or medical help is sought. Sneezing, coughing, and nasal secretions need to be kept away from other people; simply using tissues and disposing of them will help others. Quarantining patients is usually not warranted, but such measures depend on the severity of the disease.

Is swine flu (H1N1) a cause of an epidemic or pandemic in 2009?
An epidemic is defined as an outbreak of a contagious disease that is rapid and widespread, affecting many individuals at the same time. The swine flu outbreak in Mexico fits this definition. A pandemic is an epidemic that becomes so widespread that it affects a region, continent, or the world. As of April 2009, the H1N1 swine flu outbreak does not meet this definition. However, as of June 11, 2009, WHO officials determined that H1N1 2009 influenza A swine flu reached WHO level 6 criteria (person-to-person transmission in two separate WHO-determined world regions) and declared the first flu pandemic in 41 years. To date, the flu has reached 74 different countries on every continent except Antarctica in about three month's time; fortunately, the severity of the disease has not increased.

What is the prognosis (outlook) for patients that get swine flu (H1N1)?
The following is speculation on the prognosis for swine flu (H1N1) because this disease has only been recently diagnosed and the data is changing daily. This section is based on currently available information.

In general, the majority (about 90%-95%) of people that get the disease feel terrible (see symptoms) but recover with no problems, as seen in patients in both Mexico and the U.S. Caution must be taken as the swine flu (H1N1) is still spreading and may become a pandemic. So far, young adults have not done well, and in Mexico, this group currently has the highest mortality rate, but this data could quickly change. The first traceable case in Mexico, termed "patient zero," was a 5-year-old child in Veracruz who has completely recovered. Investigators noted that large pig farms were located close to the boy's home. The first death in the U.S. occurred in a 23-month-old child who was visiting Texas from Mexico but apparently caught the disease in Mexico.

People with depressed immune systems historically have worse outcomes than uncompromised individuals; investigators suspect that as swine flu (H1N1) spreads, the mortality rates may rise and be high in this population. Unfortunately, the problem with the prognosis is still unclear. If the mortality is like the conventional flu that causes mortality rates of about 0.1%, the result would be about 35,000 deaths per year because of the huge number of people that get infected. If the Mexico swine flu (H1N1) ends up with a mortality rate of about 6% and infects the same number of millions of people as conventional flu viruses, the projected numbers could be as high as 2 million deaths in the U.S. alone. This is a bad prognosis for about 2 million people and their families; these potential deaths are major reasons that health officials are so concerned about the spread of this new virus.

Another confounding problem with the prognosis of swine flu (H1N1) is that the disease is occurring and spreading in high numbers at the usual end of the flu season. Most flu outbreaks happen between November to the following April, with peak activity between late December to March. This outbreak is not following the usual flu pattern. Some scientists think that swine flu (H1N1) will quickly die out in the summer and may not ever return, while others think it may die down but return with many more cases in the fall, and still others speculate it will become a pandemic that will resemble the outcomes similar to the 1918 influenza pandemic. Some suggest it may resemble the SARS (severe acute respiratory syndrome caused by a coronavirus strain) outbreak in 2002-2003 in which the disease spread to about 10 countries with over 7,000 cases, over 700 deaths, and a 10% mortality rate. Effective isolation of patients was done in this case, and many investigators think the outbreak was stopped due to this measure. Because swine flu (H1N1) is a new virus and does not seem to be following the usual flu disease pattern, any prognosis is speculative.

Where can I find more information about swine flu?
For additional information see the following:
http://www.cdc.gov/swineflu/ (Note: This site is updated daily with ongoing information on swine flu [H1N1].)
http://www.cdc.gov/swineflu/clinician_pregnant.htm
http://wwwn.cdc.gov/travel/
http://www.medicinenet.com/influenza/article.htm
http://emedicine.medscape.com/article/219557-overview
Swine Flu Guide

Timeline update H1N1 2009 swine flu
This timeline is provided to keep readers updated on subjects, information, and data related to the flu outbreak first noted in Mexico in 2009 and to augment the information found in the article written above. Updates are written by Dr. Charles Davis.

6/11/09: WHO director Dr. Margaret Chan announced a level 6 pandemic for H1N1 2009 influenza A swine flu. The decision to declare a pandemic was reached after widespread human-to-human transmission was reached in another WHO-designated region of the globe (Australia), thus fulfilling the WHO level 6 pandemic criteria. However, officials reminded everyone that declaration of a pandemic for H1N1 flu does not indicate any major change in either the way countries respond to the disease or that the H1N1 flu has any major change in its characteristic presentation, it just indicates there is worldwide spread. The WHO suggests there is no increase in severity of symptoms of the 2009 H1N1 flu. The WHO has also not suggested any travel restrictions due to the level 6 pandemic. The WHO said that H5N1 flu is still at WHO level 3 and remarks how unusual it is to concurrently have two types of flu at these two levels. They also express caution because the H1N1 can change, and although it seems relatively stable, they express concern that it might change when the northern hemisphere enters flu season this fall. Today, the WHO reports about 28,744 H1N1 infections in 74 countries with 144 deaths around the world. The first cases on the African continent have been detected in Egypt. In a related news release, four major vaccine producers are in the early stages of H1N1 vaccine development.

6/9/09: WHO administrator Dr. Keiji Fukuda said the WHO is close to announcing a level 6 pandemic alert because of the rapid spread (over 1,000 cases reported with about 125 new cases daily) of H1N1 in Australia. The WHO has been criticized by some flu experts who think countries have pressured the WHO not to declare a pandemic. WHO officials say they are waiting to verify case reports in several countries before they declare level 6 (pandemic). The WHO has not declared a level 6 pandemic in the last 41 years.

6/7/09: The WHO reports 21,940 cases and 125 deaths worldwide.

6/5/09: Wisconsin continues to report the highest number of confirmed and suspected cases in the U.S. (2,217, an increase of 603 cases in four days). Total U.S. cases are 13,217 with 27 deaths.

6/3/09: The WHO reports that the U.S. and Australia reported the highest number of new cases in the last reporting period (1,078 and 204, respectively).

6/1/09: The CDC reports that to date there are 10,053 confirmed and probable cases of H1N1 swine flu in the U.S. with Wisconsin having the most cases (1,641). The CDC estimates that only about one in 20 cases are reported, so the CDC suggests the actual number of U.S. cases is about 200,000 cases. There have been 17 deaths reported in the U.S. Most of the cases of H1N1 currently produce mild flu symptoms. The WHO reports H1N1 swine flu in 62 countries with a total of 15,410 cases and 115 deaths. There are no cases reported on the African continent to date. Public-health officials have dropped the term "swine flu" and now use "2009 H1N1 flu" since pigs are not transmitting the disease.

5/29/09: The WHO reports that a total of 53 countries now have confirmed a total of 15,510 cases of H1N1 swine flu with a total of 99 deaths. As of today, 8,975 cases have been confirmed in the U.S. with 15 deaths. The U.S. has the highest number of confirmed cases and Mexico the highest number of deaths (85). The high number of confirmed U.S. cases may be due to testing methods available in almost every U.S. state. Today, Chinese officials released 21 U.S. students after five days of quarantine when an individual on their flight developed swine flu.

5/28/09: Australia advises about 2,000 passengers on a cruise ship docked in Sydney to quarantine themselves after at least nine confirmed cases of swine flu were found.

5/26/09: Sanofi Pasteur announces it has obtained a $190 million contract from the U.S. government to produce a swine flu vaccine. In Kuwait, 18 U.S. soldiers are reported to have swine flu.

5/23/09: CDC researchers suggest that analysis of over 50 strains of H1N1 are closely related and suggest that a single flu vaccine will likely target most, if not all, of the currently detected strains. They further suggest these findings would facilitate making an effective vaccine. The Department of Health and Human Services set aside about $1 billion for vaccine development on Friday. The WHO reports 43 countries with a total of 12,022 confirmed H1N1 cases and 86 deaths.

5/22/09: The CDC reports that only 1% of the reportedly confirmed H1N1 swine flu cases have occurred in people older than 65 years of age, while the majority of cases occurred in people 5-24 years of age. The officials speculate that older people may have been exposed to viruses in the 1930s-1950s that share some antigenic similarity to H1N1 strains and thus may provide some resistance to the virus.

5/20/09: The WHO reports 11,034 confirmed cases worldwide with a total of 85 deaths from H1N1 swine flu. To date, the WHO has not upgraded to a level 6 (pandemic); it is still at a level 5. Although CDC officials consider H1N1 to be widely spread in the U.S., WHO officials are waiting to see if H1N1 flu becomes widespread in other countries before raising the level to 6.

5/19/09: New York increases its school closings to 17 due to the numbers of suspected cases of H1N1 swine flu. WHO Director-General Dr. M. Chan addressed World Public Health Representatives today and said that the current pattern of mild illness with few deaths continues for H1N1. She cautioned the officials that because influenza viruses change rapidly, the viruses may have given everyone a "grace period" of time to better understand and treat the disease. She is concerned that the virus may interact with the H5N1 avian influenza virus populations that are "firmly established in poultry in several countries." CDC officials have estimated that about 100,000 people in the U.S. are infected with the flu virus and about half that number is infected with H1N1 swine flu; the confirmed case numbers are much smaller (5,123 cases as of May 19).

5/18/09: New York closes 11 schools after a school administrator died after getting H1N1 swine flu. The WHO is starting a conference today (World Health Assembly) about key public-health issues; the flu is likely to be a major topic of this conference. The WHO reports 40 countries are now positive for H1N1 swine flu (as compared to 29 countries reported by the WHO on May 10), with a total of 8,829 confirmed cases and 74 deaths.

5/17/09: The CDC publishes figures on the types of flu viruses reported from May 2 to May 9; the majority of isolates were novel influenza A H1N1 (34.3%) and influenza A viruses that were either unsubtyped or unsubtypable (total 40.2%). The unsubtypable viruses are thought to be variations of the novel influenza A H1N1 virus. They further report that novel influenza H1N1 virus is "antigenically and genetically unrelated to seasonal influenza A (H1N1)" and suggest that little or no protection would be afforded by current seasonal influenza vaccines. They do report some good news; to date, all tested isolates (96) of novel influenza A H1N1 are susceptible to both oseltamivir and zanamivir. However, the CDC reports that seasonal influenza A H1N1 is only sensitive to zanamivir. For more details about these reports, see http://www.cdc.gov/flu/weekly/pdf/External_F0918.pdf; data and graphs are available.
5/15/09: The WHO reports, to date, that 34 countries have officially reported a total of 7,250 cases of H1N1 swine flu worldwide. The CDC reports H1N1 has been detected in 47 states, with a total of four deaths. Confirmed and "probable" cases are totaled at 4,714 in the U.S. Several schools were closed for one week in New York when many students and some adult staff developed flu symptoms.

5/13/09: The CDC reports that a new PCR test kit (a test that detects the genetic material of the virus) for H1N1 swine flu has been produced and is being shipped to all U.S. states and also internationally. The CDC reports that a number of novel H1N1 and "unsubtypable" viruses are being detected. Novel H1N1 viruses cause a wide range of clinical symptoms such as fever, cough, sore throat, body aches, headache, chills, and fatigue and often have accompanying nausea, vomiting, or diarrhea. The CDC considers "unsubtypable" virus to be antigenic variations of the novel H1N1 virus. Some investigators suggest that H1N1 mutates rapidly because there are numerous "unsubtypable" viruses.

5/12/09: Dr. A. Schuchat, interim deputy director with the CDC, says the CDC is focusing on the coming fall flu season and that the current numbers of flu cases are increasing so fast they may consider stopping counting cases. The counted cases may only represent the tip of the iceberg for the actual number of cases. Other investigators have revised the H1N1 swine flu mortality rate to be 0.4%-1.4% of cases but reiterate that the data is still incomplete.

5/10/09: The WHO reports, to date, that 29 countries have officially reported a total of 4,379 cases of H1N1 swine flu worldwide, and the infection has reached another continent -- Australia.

5/8/09: Mexico reopens all high schools and universities today after a two-week closure. Although two more deaths were reported in Mexico (revised total number of deaths in Mexico now at 44), Health Minister Jose Angel Cordova said the flu cases were declining. Argentina, Brazil, and Colombia are the first South American countries to report H1N1 swine flu cases. World Health Organization (WHO) authorities say that up to 2 billion people could be infected if the H1N1 swine flu becomes a two-year pandemic. Confirmed H1N1 cases have been detected in two more U.S. states for a total of 43 states.

5/7/09: Currently, at least 41 U. S. states have reported confirmed cases of H1N1 swine flu. The southern hemisphere is beginning the fall/winter season, and epidemiologists and other researchers plan to closely monitor this area of the world to see if H1N1 swine flu increases in numbers of cases and severity. Some investigators suggest that how H1N1 infects populations in southern hemisphere countries (for example, New Zealand) over the next few months will help predict what N1H1 will do in the upcoming flu season of the northern hemisphere. The WHO has reported H1N1 swine flu cases confirmed in 23 countries with a total of 2,099 cases. The WHO published revised case and death numbers in Mexico to 1,112 cases and 42 deaths; this shows a marked reduction in both cases and deaths from the numbers reported by Mexico about one week ago.

5/6/09: An announcement from vaccine producers and U.S. government sources suggests that a vaccine is being developed for the more common seasonal flu virus strain and that a second vaccine is being made specific for the H1N1 2009 swine flu virus. Authorities suggest that this second vaccine is likely to require an initial injection followed by another injection at a later date. They project this requirement because people have not been exposed to H1N1 and to get a good immune response, people will need a "booster shot" (a second immunization) to enhance a person's immune response to the new H1N1 virus. Consequently, a total of three vaccine shots for the 2009-2010 flu season will likely necessary to provide an immune response that may protect individuals from the various flu viruses. Many doctors think that obtaining three, instead of one, vaccine inoculations will hamper attempts to vaccinate the general population. The WHO said about 1,600 cases of H1N1 are confirmed in about 23 countries worldwide.

5/5/09: The first U.S. death reportedly due to H1N1 virus was reported in Texas in a 33-year-old woman with multiple health issues. Over 400 schools are closed nationwide, but investigators suggest this has not been effective and suggest schools be opened since the virus is already being passed person-to-person in over 35 U.S. states. Mexico today began reducing restrictions on businesses and allowing shops to open because flu cases have begun to decline and the severity of the disease seems much less than first thought.

5/4/09: The U.S. reports a total of over 200 cases of H1N1 swine flu confirmed in about 31 states; currently, there have been no fatalities other than one child (with additional health issues) in Texas that got the disease while in Mexico. CDC officials have cautious optimism that this epidemic may not cause as many severe cases as first thought.

5/3/09: Reports from Egypt indicate many pig farms are killing off their pigs in an effort to prevent spread of "swine flu." Most investigators think this drastic step is not warranted. Canadian officials suggest a pig farm in Alberta was exposed to H1N1 virus when a farmer who visited Mexico returned. The officials say that pigs that test positive for H1N1 are being isolated. This is the first report of H1N1 infection transferred from an infected human to pigs.

5/2/09: The WHO and others jointly put out a notice that said to date there is no evidence N1N1 swine flu virus is transmitted by food, and properly handled and cooked pork or pork products will not be a source of infection.

5/1/09: Pork producers agree with U.S. researchers that "swine flu" should be renamed H1N1 2009 flu because the flu cannot be caught from eating properly cooked pork products. Virus researchers agree that no flu viruses are passed to humans through processed pork products.

Editorial note by Dr. Charles P. Davis:
After about one week, several significant things have occurred with H1N1 influenza A 2009 swine flu virus infections. First, the virus has been documented to spread rapidly from Mexico to the majority of U.S. states and now across borders to Europe, Asia, and South America; it has taken only about one to two weeks to accomplish this. This is good evidence that the virus spreads rapidly from person to person and that a large number of people may develop the disease. Second, with revised data from Mexico about mortality (deaths), the disease may not be nearly as deadly as first speculated. Third, most countries' health authorities are closely monitoring the disease on a daily basis, and the WHO and other national organizations worldwide are sharing data and opening up supplies (antiviral medications). This international cooperation helps everyone to understand and treat this disease. Finally, joint efforts between government agencies and pharmacological companies have already begun to work on producing a vaccine to prevent or reduce the effects of this disease. These efforts and findings that have occurred over such a short period of time should reassure people that although they should be vigilant about ways to avoid getting this disease (especially hand washing), there is no reason to be obsessively protective or to panic about H1N1 influenza A swine flu.

Swine Flu (H1N1 Influenza Virus) At A Glance
Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs and result in nasal secretions, a barking-like cough, decreased appetite, and listless behavior.

Swine flu viruses may mutate (change) so that they are easily transmissible among humans.

The 2009 swine flu outbreak is due to infection with the so-called H1N1 virus and was first observed in Mexico.

Symptoms of swine flu in humans are similar to most influenza infections: fever (100F or greater), cough, nasal secretions, fatigue, and headache.

Two antiviral agents, zanamivir (Relenza) and oseltamivir (Tamiflu), have been reported to help prevent or reduce the effects of swine flu if taken within 48 hours of the onset of symptoms.

There is no vaccine currently available against swine flu, but vaccine development is underway.


Medical Author: Charles Davis, MD, PhD
Medical Editor: Melissa Conrad Stöppler, MD

SOURCE: Portions of this article provided by the U.S. Centers for Disease Control and Prevention

Last Editorial Review: 6/12/2009