Novel influenza A (H1N1) is a new flu virus of swine origin that first caused illness
in Mexico and the United States in March and April 2009. This virus spreads from
person to person worldwide, in much the same way that regular seasonal influenza
viruses spread. The Center for Disease Control and Prevention (CDC) has determined
that 2009 H1N1 virus is contagious and is spreading from human to human.
Illness from the new H1N1 virus has ranged from mild to severe. While most people
who have been sick have recovered without needing medical intervention, hospitalizations
and deaths from infection with this virus have occurred. One thing that appears
to be different from seasonal influenza is that adults older than 64 years do not
yet appear to be at increased risk of 2009 H1N1-related complications. CDC laboratory
studies have shown that no children and very few adults younger than 60 years old
have existing antibody to 2009 H1N1 flu virus; however, about one-third of adults
older than 60 may have antibodies against this virus. It is unknown how much, if
any, protection may be afforded against 2009 H1N1 flu by any existing antibody.
When the 2009 H1N1 outbreak was first detected in mid-April 2009, CDC began collecting,
compiling and analyzing information regarding the 2009 H1N1 flu outbreak, including
the numbers of confirmed and probable cases and the ages of these people. The information
analyzed by CDC supports the conclusion that 2009 H1N1 flu has caused greater disease
burden in people younger than 25 years of age than older people. At this time, there
are few cases and few deaths reported in people older than 64 years old, which is
unusual when compared with seasonal flu. However, pregnancy and other previously
recognized high risk medical conditions from seasonal influenza appear to be associated
with increased risk of complications from this 2009 H1N1. These underlying conditions
include asthma, diabetes, suppressed immune systems, heart disease, kidney disease,
neurocognitive and neuromuscular disorders and pregnancy.
On June 11, 2009, the World Health Organization (WHO) signaled that a pandemic of
2009 H1N1 flu was underway by raising the worldwide pandemic alert level to Phase
6, which is an indication of the spread of the new H1N1 virus, not the severity
of illness caused by the virus. Since the WHO declaration of the pandemic, the new
H1N1 virus has continued to spread, with the number of countries reporting cases
of novel H1N1 nearly doubling.
As the novel H1N1 virus has continued to spread with new outbreaks during late summer/early
fall 2009, the CDC anticipates that there will be more cases, more hospitalizations
and more deaths associated with this pandemic in the United States. The novel H1N1
virus, in conjunction with regular seasonal influenza viruses, poses the potential
to cause significant illness with associated hospitalizations and deaths during
the U.S. influenza season. WHO is advising countries in the northern hemisphere
to prepare for a second wave of pandemic spread during the fall of 2009.
Current evidence points to some important differences between patterns of illness
reported during the pandemic and those seen during seasonal epidemics of influenza.
The age groups affected by the pandemic are generally younger. This is true for
those most frequently infected, and especially so for those experiencing severe
or fatal illness. To date, most severe cases and deaths have occurred in adults
under the age of 50 years, with deaths in the elderly comparatively rare. This age
distribution is in stark contrast with seasonal influenza, where around 90% of severe
and fatal cases occur in people 65 years of age or older.
source: http://www.cdc.gov/h1n1flu/qa.htm
source:
http://www.who.int/csr/disease/swineflu/notes/h1n1_second_wave_20090828/en/index.html
Masks for H1N1
Human cases of H1N1 (swine influenza A) viral infections have been confirmed, and
investigations of these cases suggest human-to-human contact is transmitting this
virus. The CDC recommends that all health care personnel entering rooms of patients
with suspected or diagnosed H1N1 influenza wear a fit-tested N95 or PAPR respirator.
Note: This recommendation differs from that of using surgical mask
precautions taken for seasonal influenza. The rationale is that “a more conservative
approach is needed until more is known about the specific transmission characteristics
of this new virus” (http://www.pandemicflu.gov/plan/health care/maskguideancehc.html).
The use of facemasks may be considered as an alternative to respirators; however,
they are not as effective in preventing inhalation of small particles which is one
potential route of transmission. Additionally, there is limited evidence available
suggesting that using a respirator without fit-testing may still provide better
protection than a facemask against inhalation of small particles. Respirators are
not recommended for children or those who have facial hair.
Those with H1N1 virus infection should be considered potentially contagious from
one day before to 7 days following the onset of illness. Those persons continuing
to show signs of illness after 7 days should be considered potentially contagious
until their symptoms resolve. Children may be contagious for longer periods.
Additional information on N95 respirators and other types of respirators can be
found at:
http://www.cdc.gov/niosh/npptl/topics/respirators/factsheets/respfact.html,
and at http://www.fda.gov/cdrh/ppe/masksrespirators/html
Filtering Face-Piece Respirator (N-95): The commonly known "N-95"
filtering face-piece respirator is one type of particulate respirator, often used
in hospital to protect against infectious agents. Particulate respirators are the
simplest, least expensive, and least protective of the respirator types available.
These respirators only protect against particles. They do not protect against chemicals,
gases, or vapors, and are intended only for low hazard levels. Particulate respirators
are "air-purifying respirators" because they clean particles out of the
air as you breathe. Even if you can't see the particles, there may be too many in
the air for this respirator to provide adequate protection.
Powered Air-Purifying Respirator (PAPR): Powered air-purifying
respirators use a fan to blow air through the filter to the user. They are easier
to breathe through and they need a fully charged battery to work properly. They
use the same filters as gas masks, so you need to know what the hazard is, and how
much of it is in the air.
Surveillance of Health Care Personnel
In communities where novel H1N1 virus transmission is occurring, health care personnel
should be monitored daily for signs and symptoms of febrile respiratory illness.
Health care personnel who develop these symptoms should be instructed not to report
to work, or if at work, should cease patient care activities and notify their supervisor
and infection control personnel.
In communities without novel H1N1 virus transmission, health care personnel working
in areas of a facility where there are patients being assessed or isolated for novel
H1N1 infection should be monitored daily for signs and symptoms of febrile respiratory
infection. This would include health care personnel exposed to patients in an outpatient
setting or the emergency department. Health care personnel who develop these symptoms
should be instructed not to report to work, or if at work, should cease patient
care activities and notify their supervisor and infection control personnel.
See Interim Guidance on Antiviral Recommendations for Patients with Novel Influenza
A (H1N1) Virus Infection and Their Close Contacts.
source: http://www.cdc.gov/h1n1flu/guidelines_infection_control.htm
