|
INFECTIOUS DISEASES Allana
Sucher, Section Advisor
Outbreak of H1N1 in the United States
Key point: Two epidemiologically unlinked cases with
novel swine-origin influenza A virus (H1N1) were identified in the
United States in April; as of May 5, a total of 642 confirmed cases have
been reported in 41 states.
Finer points: According to an epidemiologic analysis
recently published in the New England Journal of Medicine, on
April 15 and 17, CDC identified two unlinked cases of an H1N1 virus with
a unique genome composition that had not been previously identified in
humans or swine. As of May 5, the age range for patients infected with
H1N1 was 3 months to 81 years. 60% of patients were 18 years of age or
younger and 5% were older than 51 years. The most commonly reported
symptoms were fever (94%), cough (92%), sore throat (66%), diarrhea
(25%), and vomiting (25%). Travel information was available for 381
patients, and 18% reported travel to Mexico within 7 days prior to the
onset of symptoms. Hospitalization information was available for 399
patients; 36 (9%) required hospitalization. The age range for patients
requiring hospitalization was 19 months to 51 years. Data were available
for 22 of the hospitalized patients; 1 was pregnant, 4 were children
younger than 5 years of age, and 9 had chronic medical conditions.
Fourteen patients (74%) received oseltamivir (Tamiflu—Roche) after
hospital admission. Eleven patients had confirmed pneumonia, 8 had to be
admitted to an intensive care unit, and 4 had respiratory failure
requiring mechanical ventilation. As of May 5, 18 of the 22 hospitalized
patients (82%) recovered, 2 patients remained critically ill, and 2
patients died.
What you need to know: Most U.S. cases of H1N1
infection have comprised a self-limited, uncomplicated, febrile
respiratory illness with symptoms similar to seasonal influenza. The
fact that 60% of patients were age 18 years or younger may indicate that
children and young adults are more susceptible to infection. The mode of
viral transmission is not known; however, it is most likely to occur via
coughing or contact with infected gastrointestinal or respiratory
fluids. The incubation period for infection appears to be 2 to 7 days,
and viral shedding studies to determine the infectious period are
ongoing. Persons who are at high risk for severe complications from H1N1
infection appear to be similar to those who would be at high risk for
complications with seasonal influenza. Genetic and phenotypic testing
indicates that H1N1 is susceptible to oseltamivir and zanamivir
(Relenza—GlaxoSmith Kline) but resistant to rimantadine and
amantadine. CDC recommends prioritizing the use of neuraminidase
inhibitors for hospitalized patients with suspected or confirmed H1N1
infection and for patients at high risk for complications. Emergency use
of oseltamivir for chemoprophylaxis in infants older than 3 months and
treatment of H1N1 in infants under the age of 1 year has been approved
by FDA. Seasonal flu vaccination is not anticipated to provide
protection for this novel swine-origin H1N1 strain because it is
different from the strain represented in the 2008–2009 influenza
vaccine. According to investigators, the number of reported cases of
this strain of H1N1 is likely less than the actual number of persons
affected by the virus. Updated online resources for the pre-vention and
management of H1N1 from the New England Journal of Medicine
Influenza Center, CDC, and the Department of Health & Human Services
are available.
What your patients need to know: Tell patients that
there is no vaccine currently available to protect against this novel
influenza virus. Patients should take everyday actions (e.g., wash their
hands frequently, cover their nose and mouth when coughing or sneezing,
and avoid touching their eyes, nose, or mouth) to avoid infection and
transmission of the virus. Advise patients to stay home if they are sick
in order to limit exposure to others.
Sources:
Related resource on www.pharmacist.com:
Alex Egervary (aegervary@aphanet.org)
Posted June 15, 2009
|
