Update on Swine Influenza - April 28, 2009

It is best to begin today's installment of swine influenza information and update by explaining a few features of the current swine flu for which we all have the same questions.

"Normal" swine influenza originates in pigs, but can be passed to humans. It rarely passes from human to human. Pigs may be infected by swine, human and bird influenza viruses, sometimes simultaneously. When this occurs, a new genetic combination(s) of the virus may be capable of infecting humans. Because the new combination is not something to which humans have been previously exposed, the humans may have little or no immunity, and the virus can then spread quickly human to human. The intensity of the illness depends on the particular genetic combination, and may range from mild to severe. The H1N1 swine influenza virus is made up of genetic material from bird (avian), pig and human viruses. Since it appears to be a new combination, it may spread rapidly. So far, although deaths have been reported, there are also many reports of mild cases, so we do not know enough yet about the clinical presentation(s) to draw any conclusions about the number of persons who might become seriously ill. However, because the influenza viruses currently in circulation may become modified, the spectrum of clinical illness may worsen (or improve). It is not yet known why the current cases of swine flu in Mexico appear to be worse than those afflicting persons in the U.S. and rest of the world.

Avian flu is characterized by the H5N1 virus. It mostly spreads from infected birds to humans, and does not appear to easily transmit from human to human, although this may change.

Back to swine flu: The symptoms are fever and any combination of cough, sore throat, runny nose, body aches, headaches, chills, fatigue, and sometimes diarrhea and/or vomiting. These are typical flu symptoms, and also common symptoms with many viral respiratory and gastrointestinal infections. So, there is nothing unique about the clinical presentation as compared to that during a typical flu season.

If you develop any of these symptoms, you may be treated with oseltamivir (Tamiflu) or zanamivir (Relenza), the sooner the better (e.g., within the first two days of infection). These don't cure the disease, but may shorten the course of the infection and diminish symptoms. The drugs require a prescription. They may also be used to prevent the disease in persons who have been exposed, but this will not always be advised, particularly if it turns out that the vast majority of swine flu cases are mild.

The vaccine that has been distributed for this flu season is unlikely to prevent swine flu. The vaccine that was developed to immunize against swine flu in 1976 would likely not work, and is not available anyway. The Centers for Disease Control are working on a vaccine against the current virus, but this will take months to achieve mass production.

If you become ill with the flu (or any communicable illness like a "cold"), then take precautions to limit the spread of your illness. If you are coughing or sneezing, cover your mouth and nose. Stay home from work and school until you are well (e.g., without symptoms for at least 48 hours). Wash your hands before handling food or eating, and use alcohol-based disinfectant gel. If you touch your mouth and nose, you will be picking up the virus so that the next object(s) you touch becomes capable of transmitting the disease. A properly fitted N95 mask should be worn if you must travel or be in public while ill.

Eating pork does not transmit swine influenza.

Here is a synopsis of what was provided today by the Center for Biosecurity at the University of Pittsburgh Medical Center:

Border Closures

Following advice from an expert panel, the World Health Organization (WHO) recommended that nations SHOULD NOT close borders or restrict international travel to control swine flu.

Rapid Influenza Tests Have Limited Utility for Swine Flu

The diagnosis of swine flu cannot be definitively established with rapid testing. Rapid influenza antigen tests have moderate sensitivity and cannot be used to rule out influenza infection. Additionally, if a rapid test is positive, that result only indicates the presence of influenza A and/or B, not the type of influenza virus present. If an individual infected with swine flu tests positive for influenza A on a rapid test, the result is currently indistinguishable from that of an individual infected with seasonal influenza A.

FDA Issues Authorizations for Emergency Use of Antivirals (EUAs) and Diagnostic Tests

On April 27, 2009, the U.S. Food and Drug Administration (FDA) issued authorizations for EUAs in response to requests by the Centers for Disease Control and Prevention (CDC) for the swine flu outbreak. One of the reasons the authorizations could be issued was because the U.S. Department of Health and Human Services (HHS) declared a public health emergency on April 26, 2009.

The swine influenza EUAs do several things to aid in the current response:

Tamiflu: Allow for Tamiflu to be used to treat and prevent influenza in children under 1 year of age, and to provide alternate dosing recommendations for children older than 1 year. Tamiflu is currently approved by the FDA for the treatment and prevention of influenza in patients 1 year and older.

Tamiflu and Relenza: Allow for both antivirals to be distributed to large segments of the population without complying with federal label requirements that would otherwise apply to dispensed drugs, and to be accompanied by written information about the emergency use of the medicines.

Diagnostic Test: Allow the CDC to distribute the rRT-PCR Swine Flu Panel diagnostic test to public health and other qualified laboratories that have the equipment and personnel to perform and interpret the results.

Epidemiology Update

As of today, a total of 64 cases of swine flu have been confirmed in 5 states: 45 in New York; 1 in Ohio; 2 in Kansas; 10 in California; and 6 in Texas. In a CDC conference call, Acting Director Richard Besser gave additional details on cases that have been confirmed to date:

Five patients have been hospitalized. The CDC expects to find additional hospitalizations, which is typical for seasonal influenza.

The incubation period for swine influenza is currently estimated at 2 to 7 days.

New Zealand, Scotland, Spain, Canada, and Israel have also confirmed cases. Several other countries have suspected, but not laboratory-confirmed cases.

On April 27, 2009, the CDC and the State Department issued a travel advisory that recommends against all non-essential travel to Mexico. This travel advisory will stay in effect until public health officials determine that the risk from the flu outbreak has sufficiently subsided.

FROM THE DEPARTMENT OF HOMELAND SECURITY:

Who has the authority to order quarantines?

Local, state, and federal public health officials can issue quarantines under each jurisdiction’s legal authority. At the state and local level, each state has varying laws for implementing quarantines. Most, however, allow for local and state public health agencies to issue quarantine orders supported by local law enforcement.

At the federal level, the Department of Justice (DOJ) has established legal federal authorities pertaining to the implementation of a quarantine and enforcement. Under approval from HHS, the Surgeon General has the authority to issue quarantines necessary to prevent the introduction, transmission or spread of communicable diseases.

In addition, U.S. Customs and Coast Guard Officers assist in the enforcement of quarantine orders. Other DOJ law enforcement agencies including the U.S. Marshals, Federal Bureau of Investigation (FBI), and Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) may also enforce quarantines. Military personnel are not authorized to engage in enforcement.

Preview the Annual Meeting of the Wilderness Medical Society, which will be held in Snowmass, Colorado July 24-29, 2009.

Join me from January 24 to February 2, 2010 for an exciting dive and wilderness medicine CME adventure aboard the Nautilus Explorer to Socorro Island, Mexico to benefit the Wilderness Medical Society.

Tags: influenza, swine flu, flu, swine influenza, wilderness medicine, outdoor medicine, healthline