the symptoms and international cases of the 2009 swine flu H1N1 virus in human. swine flu is an epidemic of a new Influenza A H1N1 strain of flu virus that was clinically identified in April 2009. It is currently a Phase 5 outbreak, one level below an official pandemic.
International cases and responses of the 2009 swine flu H1N1
Although the exact origin of the outbreak is unknown, it was first detected when officials in Mexico and the United States suspected a link between an outbreak of late-season flu cases in Mexico and cases of influenza in Texas and California. Within days, hundreds more suspected cases were discovered in Mexico, with more cases also showing up in the U.S. and several other countries. By the end of April 2009, governments across the world had taken emergency measures to slow the transmission of a possible pandemic.
The new strain has spread widely beyond Mexico and the U.S., with confirmed cases in eighteen countries and suspected cases in forty-two. 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. Many countries have also issued warnings to visitors of flu-affected areas to contact a doctor immediately if they had flu-like symptoms.
Swine Flu H1N1 Symptoms
According to the Centers for Disease Control and Prevention (CDC), in humans the symptoms of the 2009 "swine flu" H1N1 virus are similar to those of influenza and of influenza-like illness in general. Symptoms include fever, cough, sore throat, body aches, headache, chills and fatigue. The 2009 outbreak has shown an increased percentage of patients reporting diarrhea and vomiting. The 2009 H1N1 virus is not zoonotic swine flu, as it is not transmitted from pigs to humans, but from person to person.
Because these symptoms are not specific to swine flu, a differential diagnosis of probable swine flu requires not only symptoms but also a high likelihood of swine flu due to the person's recent history. For example, during the 2009 swine flu outbreak in the United States, CDC advised physicians to "consider swine influenza infection in the differential diagnosis of patients with acute febrile respiratory illness who have either been in contact with persons with confirmed swine flu, or who were in one of the five U.S. states that have reported swine flu cases or in Mexico during the 7 days preceding their illness onset. A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab)
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Swine flu infects people every year and is found typically in people who have been in contact with pigs, although there have been cases of person-to-person transmission. Symptoms include fever, disorientation, stiffness of the joints, vomiting, and loss of consciousness ending in death. Swine influenza is known to be caused by influenza A subtypes H1N1, H1N2, H3N1, H3N2, and H2N3.
In swine, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are circulating throughout the world. In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages.
Swine flu in Humans
The Centers for Disease Control and Prevention (CDC) reports that the symptoms and transmission of the swine flu from human to human is much like seasonal flu, commonly fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea. It is believed to be spread between humans through coughing or sneezing of infected people and touching something with the virus on it and then touching their own nose or mouth. The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days. Diagnosis can be made by sending a specimen, collected during the first five days, to the CDC for analysis.
The swine flu is susceptible to four drugs licensed in the United States, amantadine, rimantadine, oseltamivir and zanamivir, however, for the 2009 outbreak it is recommended it be treated with oseltamivir and zanamivir. The vaccine for the human seasonal H1N1 flu does not protect against the swine H1N1 flu, even if the virus strains are the same specific variety, as they are antigenically very different.
Veterinary swine flu vaccine
Swine influenza has become a greater problem in recent decades as the evolution of the virus has resulted in inconsistent responses to traditional vaccines. Standard commercial swine flu vaccines are effective in controlling the infection when the virus strains match enough to have significant cross-protection, and custom (autogenous) vaccines made from the specific viruses isolated are created and used in the more difficult cases.
Present vaccination strategies for SIV control and prevention in swine farms, typically include the use of one of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactions with antiserum to three commercial SIV vaccines. Since the protective ability of influenza vaccines depends primarily on the closeness of the match between the vaccine virus and the epidemic virus, the presence of nonreactive H3N2 SIV variants suggests that current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses.
The current vaccine against the seasonal influenza strain H1N1 is thought unlikely to provide protection. The director of CDC's National Center for Immunization and Respiratory Diseases said that the United States' cases were found to be made up of genetic elements from four different flu viruses—North American swine influenza, North American avian influenza, human influenza A virus subtype H1N1, and swine influenza virus typically found in Asia and Europe. On two cases, a complete genome sequence had been obtained. She said that the virus is resistant to amantadine and rimantadine, but susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza)
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