Key Facts About Swine Influenza
What is Swine Influenza?
Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses cause high levels of illness and low death rates in pigs. Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.
How many swine flu viruses are there?
Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses.
Swine Flu in Humans
Can humans catch swine flu?
Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in persons with direct exposure to pigs (e.g. children near pigs at a fair or workers in the swine industry). In addition, there have been documented cases of one person spreading swine flu to others. For example, an outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.
How common is swine flu infection in humans?
In the past, CDC received reports of approximately one human swine influenza virus infection every one to two years in the U.S., but from December 2005 through February 2009, 12 cases of human infection with swine influenza have been reported.
What are the symptoms of swine flu in humans?
The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.
Can people catch swine flu from eating pork?
No. Swine influenza viruses are not transmitted by food. You can not get swine influenza from eating pork or pork products. Eating properly handled and cooked pork and pork products is safe. Cooking pork to an internal temperature of 160°F kills the swine flu virus as it does other bacteria and viruses.
How does swine flu spread?
Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with flu viruses from pigs are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Human-to-human transmission of swine flu can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the influenza virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose.
What do we know about human-to-human spread of swine flu?
In September 1988, a previously healthy 32-year-old pregnant woman was hospitalized for pneumonia and died 8 days later. A swine H1N1 flu virus was detected. Four days before getting sick, the patient visited a county fair swine exhibition where there was widespread influenza-like illness among the swine.
In follow-up studies, 76% of swine exhibitors tested had antibody evidence of swine flu infection but no serious illnesses were detected among this group. Additional studies suggest that one to three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.
How can human infections with swine influenza be diagnosed?
To diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding virus). However, some persons, especially children, may shed virus for 7 days or longer. Identification as a swine flu influenza A virus requires sending the specimen to CDC for laboratory testing.
What medications are available to treat swine flu infections in humans?
There are four different antiviral drugs that are licensed for use in the US for the treatment of influenza: amantadine, rimantadine, oseltamivir and zanamivir. While most swine influenza viruses have been susceptible to all four drugs, the most recent H1N1 influenza viruses isolated from humans are resistant to amantadine and rimantadine.
What other examples of swine flu outbreaks are there?
Probably the most well known is an outbreak of swine flu among soldiers in Fort Dix, New Jersey in 1976. The virus caused disease with x-ray evidence of pneumonia in at least 4 soldiers and 1 death; all of these patients had previously been healthy. The virus was transmitted to close contacts in a basic training environment, with limited transmission outside the basic training group. The virus is thought to have circulated for a month and disappeared. The source of the virus, the exact time of its introduction into Fort Dix, and factors limiting its spread and duration are unknown. The Fort Dix outbreak may have been caused by introduction of an animal virus into a stressed human population in close contact in crowded facilities during the winter. The swine influenza A virus collected from a Fort Dix soldier was named A/New Jersey/76 (Hsw1N1).
Swine Flu in Pigs
How does swine flu spread among pigs?
Swine flu viruses are thought to be spread mostly through close contact among pigs and possibly from contaminated objects moving between infected and uninfected pigs. Herds with continuous swine flu infections and herds that are vaccinated against swine flu may have sporadic disease, or may show only mild or no symptoms of infection.
What are signs of swine flu in pigs?
Signs of swine flu in pigs can include sudden onset of fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed.
How common is swine flu among pigs?
H1N1 and H3N2 swine flu viruses are endemic among pig populations in the United States and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months (late fall and winter) and sometimes with the introduction of new pigs into susceptible herds. Studies have shown that the swine flu H1N1 is common throughout pig populations worldwide, with 25 percent of animals showing antibody evidence of infection. In the U.S. studies have shown that 30 percent of the pig population has antibody evidence of having had H1N1 infection. More specifically, 51 percent of pigs in the north-central U.S. have been shown to have antibody evidence of infection with swine H1N1. Human infections with swine flu H1N1 viruses are rare. There is currently no way to differentiate antibody produced in response to flu vaccination in pigs from antibody made in response to pig infections with swine H1N1 influenza.
While H1N1 swine viruses have been known to circulate among pig populations since at least 1930, H3N2 influenza viruses did not begin circulating among US pigs until 1998. The H3N2 viruses initially were introduced into the pig population from humans. The current swine flu H3N2 viruses are closely related to human H3N2 viruses.
Is there a vaccine for swine flu?
Vaccines are available to be given to pigs to prevent swine influenza. There is no vaccine to protect humans from swine flu. The seasonal influenza vaccine will likely help provide partial protection against swine H3N2, but not swine H1N1 viruses.
Interim Guidance for H1N1 Flu (Swine Flu): Taking Care of a Sick Person in Your Home
This document provides interim guidance and will be updated as needed.
Swine influenza A virus infection (swine flu) can cause a wide range of symptoms, including fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting associated with swine flu. Like seasonal flu, swine flu in humans can vary in severity from mild to severe. Severe disease with pneumonia, respiratory failure and even death is possible with swine flu infection. Certain groups might be more likely to develop a severe illness from swine flu infection, such as persons with chronic medical conditions. Sometimes bacterial infections may occur at the same time as or after infection with influenza viruses and lead to pneumonias, ear infections, or sinus infections.
The following information can help you provide safer care at home for sick persons during a flu pandemic.
How Flu Spreads
The main way that influenza viruses are thought to spread is from person to person in respiratory droplets of coughs and sneezes. This can happen when droplets from a cough or sneeze of an infected person are propelled through the air and deposited on the mouth or nose of people nearby. Influenza viruses may also be spread when a person touches respiratory droplets on another person or an object and then touches their own mouth or nose (or someone else’s mouth or nose) before washing their hands.
People with swine flu who are cared for at home should:
- check with their health care provider about any special care they might need if they are pregnant or have a health condition such as diabetes, heart disease, asthma, or emphysema
- check with their health care provider about whether they should take antiviral medications
- stay home for 7 days after your symptoms begin or until you have been symptom-free for 24 hours, whichever is longer
- get plenty of rest
- drink clear fluids (such as water, broth, sports drinks, electrolyte beverages for infants) to keep from being dehydrated
- cover coughs and sneezes. Clean hands with soap and water or an alcohol-based hand rub often and especially after using tissues and after coughing or sneezing into hands.
- avoid close contact with others – do not go to work or school while ill
- be watchful for emergency warning signs (see below) that might indicate you need to seek medical attention
Sicker People More Vulnerable to Swine Flu: CDC
Underscoring the belief that the new H1N1 swine flu is no more dangerous than regular flu, U.S. health officials said Tuesday that people hospitalized for swine flu who have underlying health problems fare worse than otherwise healthy people who also have been hospitalized.
And that mirrors trends seen with seasonal -- or regular -- flu, officials said.
In an early release of the U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report, California health authorities reported on 30 people hospitalized for the H1N1 swine flu. One striking difference between these patients and patients with seasonal flu was their average age. At 27, the swine flu patients were much younger than most patients with seasonal flu who required hospitalization.
Health officials in both the United States and abroad have previously reported that the H1N1 swine flu seems to be targeting teens and young adults, unlike the regular flu which usually strikes hardest at the elderly and the very young.
Also, about two-thirds of the hospitalized patients in California had at least one underlying medical condition that put them at higher risk for influenza and its complications, Dr. Anne Schuchat, the CDC's interim deputy director for science and public health program, said during an afternoon teleconference. "The most common conditions were chronic lung disease, conditions associated with immunosuppression, chronic heart disease, obesity and pregnancy. There were five pregnant women in this series of patients," she said.
"Although the majority of hospitalized people infected with this new H1N1 virus recovered without complications, certain people did have severe and prolonged disease," Schuchat said. "None of these patients died. There are still some of these patients in the hospital, so we don't know whether they will make it or not."
Meanwhile, the World Health Organization said Tuesday that production of an H1N1 swine flu vaccine could not begin until mid-July at the earliest, which is weeks later than previous estimates. It would then take months before a vaccine would be available, the Associated Press reported.
The reason: swine flu virus isn't growing very fast in laboratories, making it hard for scientists to get the key ingredient they need for a vaccine -- the "seed stock" from the virus, WHO officials said, the AP reported.
Vaccine experts estimated that, under the best of conditions, they could produce nearly 5 billion doses of swine flu vaccine over a year after beginning full-scale production.
The WHO's director-general, Dr. Margaret Chan, said it would be impossible to produce enough vaccine for all 6.8 billion people on the planet -- a potential scenario that could pit rich countries against poorer ones as they bid for the vaccine, the AP said.
WHO officials were meeting Tuesday at their headquarters in Geneva, Switzerland, with representatives from about 30 drug companies to discuss the potential need for a vaccine and how best to produce it.
One factor complicating a decision on a swine flu vaccine is that most flu vaccine companies can only make limited amounts of both seasonal flu vaccine and pandemic vaccine, such as that needed for swine flu, and not at the same time. The producers also can't make large quantities of both types of vaccine because that would exceed manufacturing capacity.
Testing has found that the swine flu virus remains susceptible to two common antiviral drugs, Tamiflu and Relenza, according to the CDC.
In the United States, while most cases of swine flu continue to be no worse than seasonal flu, the death rate from the new H1N1 virus is slightly higher than that seen with seasonal flu, U.S. health officials said Monday.
"Our best estimate right now is that the fatality [rate] is likely a little bit higher than seasonal influenza, but not necessarily substantially higher," Schuchat said.
Schuchat added that the spread of the swine flu is far from over and could continue through the summer. "H1N1 is not going away, despite what you've heard," she said.
On Tuesday, the CDC was reporting 5,469 U.S. cases of swine flu in 48 states, and six deaths.
The World Health Organization on Tuesday was reporting 9,830 diagnosed cases in 40 countries, including at least 79 deaths, mostly in Mexico, believed to be the source of the outbreak.
The swine flu is a highly unusual mix of swine, bird and human flu viruses. Experts worry that, if the new flu virus mutates, people would have limited immunity to fight the infection.
The CDC is concerned with what will happen as the H1N1 virus moves into the Southern Hemisphere, where the flu season is about to start. The agency is also preparing for the virus' likely return in the fall to the Northern Hemisphere.
Posted in: Flu-Topic Health| Tags: Swine Flu H1N1 Flu Swine Sick HealthConsiderations on influenza A(H1N1) and HIV infection
Considerations on influenza A(H1N1) and HIV infection
Considering the potential impact of emerging influenza A(H1N1) virus infection,
HIV/AIDS programmes and services need to be aware of relevant risks and have plans
for prevention and treatment.
To date, the majority of people who contracted this virus experienced typical influenzalike
illness and recovered without treatment. However, limited preliminary information
from the United States suggests that immunocompromised persons may be at increased
risk of hospitalization. Age and other groups with increased risk for complications of the
current influenza A(H1N1) are under investigation. There is not yet any documented
information on clinical interactions between HIV and influenza A(H1N1) infection.
Individuals with immunodeficiency diseases, including HIV infection, are among highrisk
groups for complications and premature deaths from seasonal influenza and are
among the targeted groups for yearly influenza vaccination.
Although there are inadequate data to predict the impact of a possible human influenza
pandemic on HIV-affected populations, interactions between HIV/AIDS and A(H1N1)
influenza could be significant. Country preparedness plans for influenza should address
the needs of HIV-infected persons, and country HIV/AIDS plans, especially in high HIV
prevalence countries, should consider public health action required in the event of an
influenza pandemic.