TAMIFLU® (oseltamivir phosphate) has been studied only in strains of influenza that were circulating at the time. The magnitude of effect of TAMIFLU in treating and preventing novel strains of influenza, such as those that may be involved in a pandemic, cannot be predicted.
What is the difference between avian flu and pandemic flu?
Bird flu and pandemic flu are two different things. Both are a threat, but the threats they
pose to human and animal health are distinct.
Experts note that even health officials contribute to public confusion by using a single term
-bird flu-to refer to three different phenomena:
avian flu in birds
avian flu in people
pandemic flu3
Avian Flu in Birds
Avian flu is an infection caused by avian flu viruses.
These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines,
but usually do not get sick from them. However, avian flu is very contagious among birds and can make
some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.
Infection with avian flu viruses in domestic poultry causes two main forms of disease that are distinguished
by extremes of virulence, low pathogenic and highly pathogenic:
Low pathogenic form may go undetected and usually causes only mild symptoms (such as ruffled feathers
and a drop in egg production).
Highly pathogenic form, however, spreads more rapidly through flocks of poultry. This form may cause
disease that affects multiple internal organs and has a mortality rate that can reach 90% to 100%, often
within 48 hours.2
Avian Flu in Humans
During an outbreak of avian flu among poultry, there is a possible risk to people who have had contact with
infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.2
Highly pathogenic H5N1, the cause of the current concern, is an avian flu virus that had caused the death or
destruction of tens of millions of birds and, as of 5/9/06, had caused 194 cases of bird-to-human transmission
of H5N1 and 109 deaths.3
So far, the spread of the avian flu virus from person-to-person has been limited and has not continued beyond
one person. Nonetheless, because all flu viruses have the ability to change, scientists are concerned that H5N1
virus one day could infect humans and spread easily from one person to another. Because these viruses
do not commonly infect humans, there is little or no immune protection against them in the human population.
If H5N1 virus were to gain the capacity to spread easily from person-to-person, a pandemic flu could begin.2
Flu Pandemic
A pandemic flu is one that causes a global outbreak, or pandemic, of serious illness that spreads easily from
person-to-person. Currently there is no pandemic flu. A pandemic flu occurs when a new influenza type A virus
emerges for which there is little or no immunity in the human population, begins to cause serious illness, and
then spreads person-to-person worldwide.4
FOOTNOTE
2. US Dept of Health and Human Services. Centers for Disease Control and
Prevention Web site. Key facts about avian influenza (bird flu) and avian
influenza A (H5N1) virus. Available at: http://www.cdc.gov/flu/avian/gen-info/facts.htm. Accessed April 13, 2006.
3. Avian vs. pandemic flu: understanding the threat (press release). Pan American Health Organization. Available at: http://www.paho.org/english/dd/pin/pr051220.htm. Accessed April 19, 2006.
4. US Dept of Health and Human Services. What is an influenza pandemic? Available at: http://www.pandemicflu.gov/general/whatis.html. Accessed April 13, 2006.
Indications
TAMIFLU is indicated for the treatment of uncomplicated influenza caused by viruses types A and B in patients 1 year and older who have been symptomatic for no more than 2 days.
TAMIFLU is also indicated for the prophylaxis of influenza in patients 1 year and older.
TAMIFLU is not a substitute for early and annual vaccination as recommended by the Centers for Disease Control's Advisory Committee on Immunization Practices (ACIP).
Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.
Safety Information
There is no evidence for efficacy against any illness caused by agents other than influenza types A and B.
Treatment efficacy in subjects with chronic cardiac and/or respiratory disease has not been established. No difference in the incidence of complications was observed between the treatment and placebo groups in this population.
No information is available regarding treatment of influenza in patients at imminent risk of requiring hospitalization.
Efficacy of TAMIFLU has not been established in immunocompromised patients.
Safety and efficacy of repeated treatment or prophylaxis courses have not been studied.
Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease. There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving TAMIFLU. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on TAMIFLU usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of TAMIFLU to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.
In postmarketing experience, rare cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome and erythema multiforme, have been reported with TAMIFLU.
The most common adverse events reported >1% of patients treated with TAMIFLU and more commonly than in patients treated with placebo are:
Treatment of adult and pediatric patients - nausea, vomiting.
Prophylaxis of adult and pediatric patients - nausea, vomiting, abdominal pain.
Vaccination is considered the first line of defense against influenza.
