With swine flu outbreaks creating what U.S. health officials Sunday called a
public health emergency, LiveScience presents a 4-part Flu Special Report
this week to examines the science of influenza, what you can do to be safe,
and the risk of a pandemic. Part 1 today: Flu basics.
The flu virus is most commonly spread in liquid droplets made airborne by
coughing or sneezing. Symptoms – such as fever, body ache, extreme fatigue,
sore throat, and dry cough – begin showing in adults one to four days after
being infected.
The new strain of swine flu is spreading from human to human, but the
Centers for Disease Control and Prevention (CDC) doesn't yet know how
contagious it is. Bird flu, which has in recent years concerned scientists,
has been slow to transmit between humans.
A study in 2006 showed that modern travel could contribute to spreading a
flu pandemic across the United States in as little as three months.
An adult can begin spreading the flu virus one day before and three to seven
days after symptoms show, and children can remain contagious even longer.
Some infected individuals show no symptoms, yet they can still spread the
virus to others.
Among the best preventative measures you can take, according to the CDC:
* Wash hands with soap or alcohol-based sanitizers;
* Avoid touching your eyes, nose or mouth;
* avoid contact with sick people;
* and wear a face mask.
For the elderly and the young, flu vaccines can be crucial, but they only
work when designed for a specific flu strain.
Year-round problem
Many people think of the flu as a winter disease since incidence typically
peaks from December to March. It's actually a year-round problem.
But people tend to stay indoors more in the winter, making person-to-person
transmission of influenza, which is caused by a virus, easier, said Jennifer
Morcone, a spokeswoman for the CDC. Further, a study in 2007 revealed that
the influenza virus thrives on cold temperatures and low relative humidity,
allowing them to remain virulent longer in the air or on surfaces after
being sneezed out of an infected person.
Each year anywhere from 5 to 20 percent of the U.S. population gets the flu.
Anyone can contract it, but children, the elderly and people with chronic
medical conditions are more likely to experience complications, such as
pneumonia, bronchitis, and sinus and ear infections. However, the swine flu
currently sweeping through Mexico and the United States has proven more
problematic among healthy young adults.
The flu can also worsen chronic health problems: asthmatics are more likely
to have asthma attacks and people with chronic congestive heart failure may
have their condition worsen.
On average, 36,000 people in the United States die from influenza and
related complications each year, according to the CDC. More than 200,000 are
admitted to hospitals for treatment.
A pandemic in 1918 killed more than 20 million people worldwide.
The flu is sometimes confused with the common cold, and for good reason.
Both are respiratory illnesses brought on by viruses. They share many of the
same symptoms, and it is nearly impossible to make the distinction based on
the variety of symptoms alone.
Flu symptoms, however, are generally more intense, especially fever and
fatigue, and can lead to dangerous complications.
Viral roots
Influenza is a virus – a pack of protein and DNA that lacks the capacity to
self-reproduce. So it infects a cell, hijacks the inner machinery and uses
it to reproduce. The virus reproduces until there are so many copies that
the cell bursts and the virus spills out, spreading to other healthy cells.
There are three types of influenza viruses: A, B, and C. Swine flu (H1N1)
and the much hyped avian flu (H5N1) are both Type A.
Type A: Infects people, pigs, birds, horses, seals, whales, and other
animals. Wild birds are natural hosts. Divided into subtypes based on two
surface proteins – hemagglutinin (HA) and neuraminidase (NA). There are 15
HA and 9 NA subtypes, and these can be combined in various ways. Currently,
the three most common subtypes in general human circulation are H1N1, H1N2,
and H3N2. These can cause epidemics – defined as a high incidence of disease
in an area or population – and also a widespread geographic or global
disease called a pandemic.
Type B: Normally occurs only in humans. No subtypes. Known to cause human
epidemics, but not pandemics.
Type C: Only causes mild respiratory illness in humans, and is not included
in flu vaccines. Not capable of epidemic or pandemic spread.
Types A and B are further characterized into genetic variants called
"strains." New strains are constantly evolving and take the place of older
ones. While your body may have built up resistance against one strain, it
may not be able to fend off its replacement.
News of a new swine flu in humans seemed to spread faster worldwide than the
virus itself in recent days, but with that has come an army of people
whipping out thermometers and a myriad of questions about face masks and
much more. LiveScience clears up some of the misconceptions, based on advice
from the Centers for Disease Control and Prevention (CDC), recent studies,
and other experts.
How is this flu transmitted?
The flu virus, including this one - a type A/H1N1 flu virus, is most
commonly spread in liquid droplets made airborne by coughing or sneezing.
This is a highly contagious respiratory illness. For this reason, sick or
not, cover your mouth when sneezing or coughing, and wash your hands
frequently, especially after using a tissue. Don't touch your nose or mouth,
or rub your eyes. Throw away tissues after use.
Can you get the flu by eating pork?
No, the swine flu cannot be spread by eating properly cooked pork, but you
can get it from contact with infected pigs.
Is it OK to kiss someone on the cheek or lips?
There is mixed advice on this, but most authorities say that kissing and
even hugging should be avoided, if you want to avoid getting the flu.
Is it safe to shake hands?
Again, mixed advice. Frequent hand-washing will take care of uncertainties.
Should I wear a face mask?
It's a personal decision, but there is definitely evidence that face masks -
surgical ones that fit tightly against the skin - are effective at
preventing the spread of the flu and other viruses. These masks are not
necessarily the same as the dust masks that some people use when cleaning or
doing construction work. In May 2007, the CDC issued guidelines saying that
surgical masks "should be considered" during a flu pandemic for anyone sick
with the flu, anyone entering a crowd, or those living with people with flu
symptoms. This wording was a watering-down of a previously considered "face
mask should be worn" recommendation due to a lack of evidence at that time
about face masks and the flu. You can buy such face masks at drug stores and
medical supply stores.
How many people have died so far?
Although swine flu has been confirmed, as of Monday morning, in people in
five U.S. states (Texas, California, Kansas, New York and Ohio - a total of
20 cases), no one here has died of it and all these cases have been mild. In
Mexico, more than 100 people have died from the swine flu, according to
Associated Press reports from Mexican officials. No one yet knows why the
cases in Mexico are so much more severe. Some of the confirmed numbers fail
to add up, possibly due to the lag time in obtaining lab confirmations.
There were 20 lab-confirmed cases of swine influenza in humans in the United
States, and 18 lab-confirmed cases in Mexico, according to a World Health
Organization statement on Sunday. The WHO declared this event a public
health emergency of international concern Saturday, but the death rate for
swine flu tends to be low, around 1 to 4 percent, the agency says.
How do you know if you have swine flu or just some other cold or virus?
A doctor can tell, but swine flu, like other cases of influenza, starts
suddenly with symptoms such as a high fever, headache, fatigue, cough, sore
throat, runny nose and body aches. If you develop these symptoms and are
concerned, consult your doctor.
Do healthy, young adults have anything to worry about?
Yes. It's true that the flu usually is more of a threat to the very young
and very old, or people with compromised immune systems. But in this case,
swine flu has been affecting and proved problematic for people of all ages.
Everyone should take precautions, such as being more vigilant than usual
about washing their hands, not touching their eyes, mouth and nose, and
covering their mouth when sneezing or coughing.
What are the treatments for swine flu?
Treatment for swine flu is the same as any other cold or flu - stay home,
rest, drink plenty of liquids, avoid drinking alcohol and intake of tobacco,
and take pain-killers and over-the-counter aids as needed. Consult your
doctor for details. For serious cases, there are U.S. approved anti-viral
drugs including Tamiflu, Relenza, Symmetrel and Flumadine.
Is there a vaccine for swine flu?
There is currently no vaccine for the current swine flu in humans. Vaccines
typically take months to develop.
Should people avoid traveling now?
Again this is a personal decision, but it's true that the more people with
whom we have contact, the more germs we encounter, and this increases our
odds of getting sick. Many of the swine flu cases outside of Mexico, so far,
have occurred among people who recently visited there. However, the United
States has not issued any travel warnings or quarantines.
Is this worse than SARS was?
At the height of the last SARS pandemic (2002-2003), some 774 people died
(nearly 10 percent of all who caught the coronavirus that causes it). Most
of the cases were in China. There were 8 cases in the United States and no
fatalities in this country.
Is this worse than bird flu was?
Bird flu (an H5N1 virus) has killed millions of birds, and about 250 people
in 12 countries, according to the WHO.
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