CDC – What are the symptoms of swine flu (H1N1)?

Although uncomplicated influenza-like illness (fever, cough or sore throat) has been reported in many cases, mild respiratory illness (nasal congestion, rhinorrhea) without fever and occasional severe disease also has been reported. Other symptoms reported with swine influenza A virus infection include vomiting, diarrhea, myalgia, headache, chills, fatigue, and dyspnea. Conjunctivitis is rare, but has been reported. Severe disease (pneumonia, respiratory failure) and fatal outcomes have been reported with swine influenza A virus infection. The potential for exacerbation of underlying chronic medical conditions or invasive bacterial infection with swine influenza A virus infection should be considered.

CDC on Swine Flu (H1N1) – What is the swine flu?

The swine influenza A (H1N1) virus that has infected humans in the U.S. and Mexico is a novel influenza A virus that has not previously been identified in North America. This virus is resistant to the antiviral medications amantadine (Symmetrel) and rimantadine (Flumadine), but is sensitive to oseltamivir (Tamiflu) and zanamivir (Relenza). Investigations of these cases suggest that on-going human-to-human swine influenza A (H1N1) virus is occurring.

What is the prognosis (outlook) for patients who 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 who 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 has 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.

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. Current data suggest that pregnant individuals, children under 2 years of age, young adults, and individuals with any immune compromise or debilitation are likely to have a worse prognosis. 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 36,000 deaths per year because of the huge number of people who 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. As of September 2009, the current estimates are that about 90,000 deaths will occur in the U.S. from novel H1N1 swine flu (estimated by the president’s advisory committee). As of October, these estimates have not been revised by the advisory committee or the CDC.

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 since novel H1N1 began its outbreak in April and had spread throughout the world by September. Some scientists think that swine flu (H1N1) will die down but return with many more cases in the fall, and still others speculate the current pandemic will eventually 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 had 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, although as of October 2009, the numbers of people with flu-like illness are higher than usual and the illness is affecting a much younger population than the conventional flu. As the pandemic progresses, this article will be updated. The best news about this novel H1N1 swine flu is that the majority of people, as of October 2009, who have caught the flu recover without medical treatment and have an excellent prognosis.

Can H1N1 be prevented if the H1N1 flu vaccine is not readily available?

Although vaccination is the best way to “prevent” H1N1, currently (November 2009), there is not enough available for everyone who wants or needs H1N1 vaccination. Until H1N1 vaccine supplies meet demand, there are some things people can do to try and prevent infection. Without vaccination, the best strategy is to not allow H1N1 virus to contact a person’s mucus membranes because if the virus does not reach cells in which it can grow, it cannot cause infection. Quarantining H1N1-infected people is an extreme measure that may work in some instances (for example, China uses this method), but even with quarantining, the virus may still spread by people who have minimal or no symptoms.

The next step that is easier to be implemented by individuals is for people with the disease to self-quarantine until they become noninfectious (about seven to 10 days after flu symptoms abate). Infected people can wear surgical masks to reduce the amount of droplet spray from coughs and sneezes and throw away contaminated tissues. Unfortunately, these approaches depend on the compliance of many other people, and the likelihood that such methods will be highly successful in preventing H1N1 infections, at best, is only fair. Such methods have not stopped the current pandemic. Yet there are still some other methods available to individuals. Perhaps the best way for individuals to try to prevent H1N1 infection is a combination of methods that are aimed at fulfilling the very basic principle that if H1N1 doesn’t reach an individual’s mucus membrane cells, infection will be prevented. The methods are as follows:

1. Kill or inactivate the virus before it reaches a human cell by using soap and water to clean your hands; washing clothing and taking a shower will do the same for the rest of your body.

2. Use an alcohol-based hand sanitizer if soap and water are not readily available.

3. Use sanitizers on objects that many people may touch (for example, doorknobs, computer keyboards, handrails, phones).

4. Do not touch your mouth, eyes, nose, unless you first do items 1 or 2 above.

5. Avoid crowds, parties, and especially people who are coughing and sneezing (most virus-containing droplets do not travel more than 4 feet, so experts suggest 6 feet away is a good distance to stay). If you cannot avoid crowds (or parties), try to remain aware of people around you and use the 6-foot rule with anyone coughing or sneezing. Do not reach for or eat snacks out of canisters or other containers at parties.

6. Avoid touching anything within about 6 feet of an uncovered cough/sneeze, because the droplets that contain virus fall and land on anything usually within that range.

7. Studies show that individuals who wear surgical or N95 particle masks may prevent inhalation of some H1N1 virus, but the masks may prevent only about 50% of airborne exposures and offer no protection against surface droplets. However, masks on H1N1 infected people can markedly reduce the spread of infected droplets.

These seven steps can help prevent individuals from getting H1N1 infection, but for many people, adherence to them may be difficult at best. However, there are some additional strategies that may also help prevent H1N1 infections in unvaccinated people according to some investigators. Saline nasal washes and gargling with saline (or a commercial product) as a way to reduce or eliminate H1N1 virus from mucus membranes has been suggested. Proponents of these methods base their rationale on the fact that flu viruses usually take about two to three days to proliferate in nasal/throat cells. While nasal washes and gargling may be soothing to some people, there are no studies that indicate H1N1 is killed, inactivated, or completely removed by these methods; conversely, there are no data suggesting these methods cannot have any effect on H1N1. However, with long-term nasal washes using Neti pots, sinus infection with other pathogens may be encouraged.

Other investigators and physicians have offered additional methods that may help reduce exposure to H1N1 virus. For example, Dr. Gerberding, a former CDC director, had several suggestions about how to avoid H1N1 infection on an airplane. She suggested the following:

1. If a person is next to you or near (within 6 feet) and is coughing/sneezing, ask the flight attendant to offer the person a mask.

2. If there are available seats 6 feet or more away from the coughing/sneezing person, ask to change your seat (planes are good means of travel because the air is recirculated through HEPA filters that can capture viruses, but even the filters will not help if people touch areas where droplets have landed; HEPA filters are usually not available in buses, cars, ships, or trains).

3. Turn away from the coughing/sneezing person and turn the air vent toward the person to blow the droplets away from yourself.

Variations of her suggestions may be applicable in many different social, work, or travel situations, but there are no data to prove these methods are effective. In addition, common-sense precautions such as not drinking or eating things touched by others, avoiding casual physical contacts (for example, handshakes, social hugs or kisses, public water fountains [these are OK if you touch nothing and lips only touch flowing water], banisters on stairways, and restroom door handles) will limit exposure to H1N1. Again, these common sense suggestions lack data substantiation.

Many investigators suggest that people stay well hydrated, take vitamins, and get plenty of rest, but these precautions will not prevent H1N1 infections although they may help reduce the effects of infection by strengthening the person’s immune system to fight infection. Similarly, current antiviral medications (described in the preceding section) act on H1N1 viruses that have already infected cells; they work by preventing or reducing viral particles from aggregating and being released from infected cells. Timing is important; if only a few cells are infected and the antiviral medications are administered quickly (usually before flu symptoms develop or within 48 hours), the viruses are reduced in number (they cannot easily bud out from the cell surface), so few, if any, other respiratory or mucus membrane cells become infected. This can result in either no flu symptoms or, if a larger number of cells were initially infected, less severe symptoms. The overall effect for the person is that the H1N1 infection was prevented (it was not; the symptoms were prevented from developing) or that symptoms were reduced.

In the strictest sense of the word prevention, even effective vaccines do not “prevent” infections. What they do accomplish is to alert the immune system to be on guard for certain antigens that are associated with a pathogen (for example, H1N1 virus, pneumococcal bacteria). When the pathogen first infects the host, its antigens are recognized, and these cause a rapid immunoprotective response to occur that prevents the pathogen from proliferating and developing symptoms in the host. People, including physicians and researchers, often term this complex response to vaccination as “prevention of infection” but what actually occurs is the prevention of further infection so well that symptoms do not develop or are minimal in the host.

In summary, if H1N1 viruses fail to contact cells they can infect, the disease will be prevented. As stated above, this is difficult, but not impossible, to do in almost all societies. Prevention of H1N1 symptoms of infection is possible with antiviral medications if these are given very early in the infection. There are many other methods that may reduce the chance of getting the virus on a person’s mucosal surface, but most methods have not been backed up with objective data. Most doctors and investigators suggest that items that help boost or allow the immune response to function well will help people resist H1N1 infections and reduce symptoms, but these also do not prevent infections. Consequently, while waiting for H1N1 vaccine, these are some ways individuals can improve their chances of preventing or reducing the symptoms of H1N1 infections.

What is the history of swine flu (H1N1) in humans?

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.

Can novel H1N1 swine flu be prevented with a vaccine?

The best way to prevent novel H1N1 swine flu would be the same best way to prevent other influenza infections, and that is vaccination. The CDC has multiple recommendations for vaccination based on who should obtain the first doses when the vaccine becomes available (to protect the most susceptible populations) and according to age groups. The CDC based the recommendations on data obtained from vaccine trials and infection reports gathered over the last few months. The current (October 2009) vaccine recommendations from the CDC say the following groups should get the vaccine as soon as it is available:

* pregnant women,

* people who live with or provide care for children younger than 6 months of age,

* health-care and emergency medical services personnel,

* people between 6 months and 24 years of age, and

* people from the ages of 25 through 64 who are at higher risk because of chronic health disorders such as asthma, diabetes, or a weakened immune system.

Currently, the CDC is stating that people ages 10 and above are likely to need only one vaccine shot to provide protection against novel H1N1 swine flu and further suggest that these shots will be effective in about 76% of people who obtain the vaccine. New vaccine trial data showed that healthy adults produce protective antibodies in about 98% of people in 21 days. Unfortunately, the vaccine shot in children ages 6 months to 9 years of age is not as effective as it is in older children and adults. Consequently, the CDC currently recommends that for ages 6 months up to and including 9 years of age, the children obtain two shots of the novel H1N1 vaccine, the second shot 21 days after the first shot.

Pregnant women are strongly suggested to get vaccinated as stated above. Although some vaccine preparations (multidose vials) contain low levels of thimerosal preservative (a mercury-containing preservative), the CDC still considers the vaccine safe for the fetus and mother. However, some vaccine preparations that are in single-dose vials will not have thimerosal preservative, so those pregnant individuals who are concerned about thimerosal can get this vaccine preparation when it is available.

Another type of vaccine (currently named Influenza A [H1N1] 2009 Monovalent Vaccine Live, Intranasal) has been made available during the first week in October 2009. It is a live attenuated novel H1N1 flu vaccine that contains no thimerosal, is produced by MedImmune, LLC, and is sprayed into the nostrils. This vaccine is only for healthy people 2-49 years of age, and some data suggest that it is less effective in generating an immune response in adults than the vaccine injection. The dosing schedule is as follows:

* Children 2-9 years of age should receive two doses (0.1 ml in each nostril; total equals 0.2 ml per dose) — the second dose should be given the same way about one month after the first dose

* Children, adolescents and adults, 10-49 years of age should receive one dose — (0.1 ml in each nostril; total equals 0.2 ml per dose)

The CDC occasionally makes changes and updates its information on vaccines and other recommendations about the current flu pandemic. The CDC states, “for the most accurate health information, visit http://www.cdc.gov or call 1-800-CDC-INFO, 24/7.” Caregivers should check the vaccine package inserts for more detailed information on the vaccines when they become available. This article has an updated timeline for novel H1N1 swine flu attached (see below) and provides the reader with current details about the pandemic. The following is a list of the CDC-approved H1N1 vaccines and the companies that name and manufacture them as of 10/29/09:

* Influenza A (H1N1) 2009 Monovalent Vaccine by Sanofi Pasteur

* Influenza A (H1N1) 2009 Monovalent Vaccine by Novartis

* Influenza A (H1N1) 2009 Monovalent Vaccine Live, Intranasal by MedImmune, LLC

* Influenza A (H1N1) 2009 Monovalent Vaccine by CSL Limited

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 who 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. Some investigators say that administration of these drugs is still useful after 48 hours, especially in high-risk patient populations .However, taking these drugs is not routinely recommended for prevention for the healthy population because investigators suggest that as occurs with most drugs, flu strains will develop resistance to these medications. Recently, the CDC made further suggestions about the use of these antiviral medications. Dr. Schuchat, a CDC official, indicated that three modifications were being suggested (Sept. 8, 2009) to the interim guidelines for use of Tamiflu and Relenza:

1. Patients with high-risk factors should discuss flu symptoms and when to use antiviral medications; doctors should provide a prescription for the antiviral drug for the patient to use if the patient is exposed to flu or develops flu-like symptoms without having to go in to see the doctor.

2. “Watchful waiting” was added as a response to taking antiviral medications, with the emphasis on the fact that those people who develop fever and have a preexisting health condition should then begin the antiviral medication.

3. The antiviral medications are the first-line medicines for treatment of novel H1N1 swine flu, and most current cases of flu are novel H1N1 and are, to date, susceptible to Tamiflu and Relenza.

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 is no longer transmittable (about two to three weeks) or until medical help and advice 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. The CDC recommends that people who appear to have an influenza-like illness upon arrival at work or school or become ill during the day be promptly separated from other people and be advised to go home until at least 24 hours after they are free of fever (100 F [37.8 C] or greater), or signs of a fever, without the use of fever-reducing medications. The novel H1N1 swine flu disease takes about seven to 10 days before fevers stop, but new research data (Sept. 14, 2009) suggests waiting until the cough is gone since many people are still infectious about one week after fever is gone. The CDC has not yet extended their recommendations to stay home for that extra week.

What are the symptoms of swine flu (H1N1)?

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 these initial data have been revised and the mortality rate currently in Mexico is estimated to be much lower. By June 2009, the virus had reached 74 different countries on every continent except Antarctica, and by September 2009, the virus had been reported in most countries in the world. Fortunately, the mortality rate as of October 2009 has been low but higher than for the conventional flu (average conventional flu mortality rate is about 36,000 per year; projected novel H1N1 flu mortality rate is 90,000 per year in the U.S. as determined by the president’s advisory committee).