Sunday, August 9, 2009

How serious is the Novel H1N1 influenza infection?

Since I first posted about 'Swine flu' in April a large amount of information has been accumulated about this on going pandemic. Here is an update.
What is influenza (flu)?
Influenza (flu) is a viral infection. People often use the term "flu" to describe any kind of mild illness, such as a cold or a stomach upset, that has symptoms like the flu. But the real flu is different. Flu symptoms are usually worse than a cold and last longer. The flu usually does not cause vomiting or diarrhea.
Most flu outbreaks happen in late fall and winter.
What causes the flu?
The flu is caused by influenza viruses A and B. There are different strains, or types, of the flu virus every year.
What are the symptoms?
The flu causes a fever, body aches, a headache, a dry cough, and a sore or dry throat. You will probably feel tired and less hungry than usual. The symptoms usually are the worst for the first 3 or 4 days. But it can take 1 to 2 weeks to get completely better.
It usually takes 1 to 4 days to get symptoms of the flu after you have been around someone who has the virus.
Most people get better without problems. But sometimes the flu can lead to a bacterial infection, such as an ear infection, a sinus infection, or bronchitis. In rare cases, the flu may cause a more serious problem, such as pneumonia
Certain people are at higher risk of problems from the flu. They include young children, pregnant women, older adults, and people with long-term illnesses or with impaired immune systems that make it hard to fight infection
What is Swine flu?
Novel H1N1 (referred to as “swine flu” early on) is a new influenza virus causing illness in people. The epidemic probably started in Mexico in mid-March 2009 and spread to USA in April. This virus is spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread.

The virus is being described as a new subtype of Influenza A(H1N1) not previously detected in swine or humans. The 2009 novel A(H1N1) strain contains an unusual mix of gene segments. The genetic sequencing of samples in the Centers for Disease Control (CDC) Atlanta shows that the new flu virus contains segments from four different viruses: from North American swine viruses, North American avian Viruses, human influenza, and two Eurasian swine viruses.

How does novel H1N1 virus spread?
Spread of novel H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza. Sometimes people may become infected by touching something – such as a surface or object – with flu viruses on it and then touching their mouth or nose.

What are the signs and symptoms of this virus in people?
The symptoms of novel H1N1 flu virus in people include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. A significant number of people who have been infected with this virus also have reported diarrhea and vomiting. Severe illnesses and death has occurred as a result of illness associated with this virus.
In a study of 30 c0nfirmed patients from USA the most common admission diagnoses were pneumonia and dehydration. Nineteen patients (64%) had underlying medical conditions; the most common were chronic lung disease (e.g., asthma and chronic obstructive pulmonary disease), conditions associated with immunosuppresion, chronic cardiac disease (e.g., congenital heart disease and coronary artery disease), diabetes, and obesity. The most common symptoms were fever, cough, vomiting, and shortness of breath; diarrhea was uncommon. Of the 25 patients who had chest radiographs, 15 (60%) had abnormalities suggestive of pneumonia, including 10 with multilobar infiltrates and five with unilobar infiltrates.
How severe is illness associated with novel H1N1 flu virus?
Illness with the new H1N1 virus has ranged from mild to severe. While most people who have been sick have recovered without needing medical treatment, hospitalizations and deaths from infection with this virus have occurred. The case fatality of this current epidemic is estimated by some experts as around 0.2%
In seasonal flu, certain people are at “high risk” of serious complications. This includes people 65 years and older, children younger than five years old, pregnant women, and people of any age with certain chronic medical conditions. About 70 percent of people who have been hospitalized with this novel H1N1 virus have had one or more medical conditions previously recognized as placing people at “high risk” of serious seasonal flu-related complications. This includes pregnancy, diabetes, heart disease, asthma and kidney disease.
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 novel H1N1-related complications thus far.
CDC laboratory studies have shown that children and few adults younger than 60 years old do not have existing antibody to novel 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 novel H1N1 flu by any existing antibody.
How long can an infected person spread this virus to others?
People infected with seasonal and novel H1N1 flu shed virus and may be able to infect others from 1 day before getting sick to 5 to 7 days after. This can be longer in some people, especially children and people with weakened immune systems and in people infected with the new H1N1 virus.

Prevention & Treatment
What can I do to protect myself from getting sick?

There is no vaccine available right now to protect against novel H1N1 virus. However, a novel H1N1 vaccine is currently in production and may be ready for the public by September. As always, a vaccine will be available to protect against seasonal influenza There are everyday actions that can help prevent the spread of germs that cause respiratory illnesses like influenza.
Take these everyday steps to protect your health:
Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hand cleaners are also effective.
Avoid touching your eyes, nose or mouth. Germs spread this way.
Try to avoid close contact with sick people.
If you are sick with flu-like illness, it is recommended that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.) Keep away from others as much as possible to keep from making others sick.
Other important actions that you can take are:
Follow public health advice regarding school closures, avoiding crowds and other social distancing measures.
Be prepared in case you get sick and need to stay home for a week or so; a supply of over-the-counter medicines, alcohol-based hand rubs, tissues and other related items might could be useful and help avoid the need to make trips out in public while you are sick and contagious.
If I have a family member at home who is sick with novel H1N1 flu, should I go to work?
Employees who are well but who have an ill family member at home with novel H1N1 flu can go to work as usual. These employees should monitor their health every day, and take everyday precautions including washing their hands often with soap and water, especially after they cough or sneeze. If they become ill, they should notify their supervisor and stay home. Employees who have an underlying medical condition or who are pregnant should call their health care provider for advice, because they might need to receive influenza antiviral drugs to prevent illness.
What should I do if I get sick?
If you live in areas where people have been identified with novel H1N1 flu and become ill with influenza-like symptoms, including fever, body aches, runny or stuffy nose, sore throat, nausea, or vomiting or diarrhea, you should stay home and avoid contact with other people. Stay away from others as much as possible to keep from making others sick.Staying at home means that you should not leave your home except to seek medical care. This means avoiding normal activities, including work, school, travel, shopping, social events, and public gatherings.
If you have severe illness or you are at high risk for flu complications, contact your health care provider or seek medical care. Your health care provider will determine whether flu testing or treatment is needed.
If you become ill and experience any of the following warning signs, seek emergency medical care.
In children, emergency warning signs that need urgent medical attention include:
Fast breathing or trouble breathing
Bluish or gray skin color
Not drinking enough fluids
Severe or persistent vomiting
Not waking up or not interacting
Being so irritable that the child does not want to be held
Flu-like symptoms improve but then return with fever and worse cough
In adults, emergency warning signs that need urgent medical attention include:
Difficulty breathing or shortness of breath
Pain or pressure in the chest or abdomen
Sudden dizziness
Confusion
Severe or persistent vomiting
Flu-like symptoms improve but then return with fever and worse cough
Are there medicines to treat novel H1N1 infection?
Yes. the use of oseltamivir or zanamivir is recommended for the treatment and/or prevention of infection with novel H1N1 flu virus. Antiviral drugs are prescription medicines (pills, liquid or an inhaled powder) that fight against the flu by keeping flu viruses from reproducing in your body. If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. During the current pandemic, the priority use for influenza antiviral drugs is to treat severe influenza illness (for example hospitalized patients) and people who are sick who have a condition that places them at high risk for serious flu-related complications.
All patients with Novel H1N1 flu need not take the anti-viral medicines.
Antiviral treatment with either oseltamivir or zanamivir is recommended for all patients with confirmed, probable or suspected cases of novel influenza A (H1N1) virus infection who are hospitalized or who are at higher risk for seasonal influenza complications.
Pregnant women who gets influenza like illness in regions affected by pandemic should be started on anti-viral medicines as soon as possible even before confirming the diagnosis.

Our understanding of the disease continues to evolve as new countries become affected, as community-level spread extends in already affected countries, and as information is shared globally. Many countries with widespread community transmission have moved to testing only samples of ill persons and have shifted surveillance efforts to monitoring and reporting of trends. This shift has been recommended by WHO, because as the pandemic progresses, monitoring trends in disease activity can be done better by following trends in illness cases rather than trying to test all ill persons, which can severely stress national resources. It remains a top priority to determine which groups of people are at highest risk of serious disease so steps to best to protect them can be taken.
Average age of cases increasing
In most countries the majority of pandemic (H1N1) 2009 cases are still occurring in younger people, with the median age reported to be 12 to 17 years (based on data from Canada, Chile, Japan, UK and the United States of America). Some reports suggest that persons requiring hospitalization and patients with fatal illness may be slightly older.
As the disease expands broadly into communities, the average age of the cases is appearing to increase slightly. This may reflect the situation in many countries where the earliest cases often occurred as school outbreaks but later cases were occurring in the community. Some of the pandemic disease patterns differ from seasonal influenza, where fatal disease occurs most often in the elderly (>65 years old). However, the full picture of the pandemic's epidemiology is not yet fully clear because in many countries, seasonal influenza viruses and pandemic (H1N1) 2009 viruses are both circulating and the pandemic remains relatively early in its development.
Although the risk factors for serious pandemic disease are not know definitively, risk factors such as existing cardiovascular disease, respiratory disease, diabetes and cancer currently are considered risk factors for serious pandemic (H1N1) 2009 disease. Asthma and other forms of respiratory disease have been consistently reported as underlying conditions associated with an augmented risk of severe pandemic disease in several countries.
A recent report suggests obesity may be another risk factor for severe disease. Similarly, there is accumulating evidence suggesting pregnant women are at higher risk for more severe disease. A few preliminary reports also suggest increased risk of severe disease may be elevated in some minority populations, but the potential contributions of cultural, economic and social risk factors are not clear.
Vaccine situation
Vaccine may be available by September against Novel H1N1 virus.

adapted from CDC and WHO websites.

5 comments:

blabberblah said...

Thanks for this article! It's really made the situation much clearer now. And it's much easier to understand than what's in the news.

indianhomemaker said...

I have linked this post to mine on Swine Flu. I think we really need this information right now. Thanks for this post, coming from a doctor it is even more reassuring.

mummyjaan said...

Useful info. And not too long a blog post to go through either :).

Charakan said...

Thank you mummyjaan

gita said...

This is a great service and a wonderful summary.