Influenza A (H1N1) in 2009

Influenza A (H1N1) in 2009
Influenza A (H1N1) or influenza A (H1N1) (originally called swine flu by the World Health Organization) is an acute contagious respiratory illness caused by one of the few influenza virus A the Influenzavirus A subtype H1N1, emerged in 2009 under a new genetic form transmissible from human to human. The flu has also been named by various international institutions, North American influenza, influenza Mexican or new influenza before the WHO does not recommend the name of influenza A (H1N1) on 30 April 2009.

The new influenza virus containing genes from several viruses known to porcine, avian and human, is a reassortant virus. There is no vaccine against this strain and WHO scientists are unaware if the existing vaccines against seasonal influenza may confer protection. People with symptoms of influenza A (H1N1) are currently treated with neuraminidase inhibitors of influenza viruses such as oseltamivir or zanamivir.

In some countries, the list is maintained by the WHO, the spread of influenza A (H1N1) epidemic is likely. In the rest of the world, the number of people affected is too small for this term is appropriate.

An important factor to measure the danger of a disease is its lethality, the proportion of deaths among those affected (mortality).

The nature of flu is not the only fatality. The degree of progress in terms of safety of the country is a factor. Margaret Chan, Director General of WHO, said: "Past experience shows us that the flu can cause mild illness in rich countries but a more severe disease with a fatality rate higher in developing countries. This rule seems to apply to influenza A (H1N1).

A journalist from the Nouvel Observateur, Mr. de Pracontal note that "patients in North America or Europe have suffered from moderate disorders, not putting their lives at risk. And they have recovered without problems, unlike in Mexico. The threat of disease, particularly for less wealthy countries, justifies the transition to phase 5 of the alert level of risk of pandemic influenza.

This state of alert is declared when there is a contamination between two humans in at least two countries in the WHO is proven and there is an imminent threat of a pandemic. It outlines the steps to be taken by countries.

On 11 June 2009, WHO decided the move to Phase 6, influenza A (H1N1) is considered a pandemic.



Morbidity is the result of the contagion. More illness is contagious, the higher the morbidity is high. Many other factors come into account, as the hygiene conditions in which a population lives, health or the precautions taken to prevent the spread of the disease.

Influenza A (H1N1) is still very recent, its morbidity is a source of more questions than precise answers. However, the general knowledge of influenza will provide some answers, still imprecise and subject to interrogation. The disease is very different, depending on the flu.

The common flu or seasonal sometimes called, has a high morbidity, it affects between 5% and 15% of the population. In contrast, avian influenza is very contagious and spreads evil in humans. On the whole planet, the number of people affected was estimated only in hundreds over the last four years. Several indicators suggest that the morbidity of influenza A (H1N1) is closer to seasonal influenza and the avian flu. The first of them comes from the virological analysis, it shows the existence of elements from swine influenza. History teaches us that having origins flu can be contagious pig as was the flu in Hong Kong in 1968.

An important factor in the danger of this virus is its ability to deploy on a more or less extensive in the world.

Some outbreaks of influenza have been local, such as Madagascar in July and August 2002 by a virus of type A (H3N2). Particularly if it was contagious, because in some areas, she touched up to 85% of the population, this epidemic has been limited to a geographical space of four of the six provinces and has not left the island. The local nature of flu is not a generality, some of them spreading over a large part of the planet, including influenza A (H1N1).

Two facts are known with certainty: the disease is transmitted from human to human without going through animals, and disease spread in different countries.

His illness remains unknown, the statistical data is too small to draw definite conclusions.

The lethality of different flu is also widely variable. She is depending on the conditions of life of populations, types of populations, and health resources of countries in which they live.

In the world, seasonal influenza kills each year between 250 000 and 500 000 people. In France, influenza kills between 1 500 and 2 000 persons per year and it kills each year about 36 000 in the United States. It does, however, that kills the fraction of the population most vulnerable: the elderly, those suffering from diseases or long-time younger children. This profile seems to be lethal for influenza A (H1N1) and for rich countries. Richard Besser, director of the federal Centers for control and disease prevention (CDC) said it was "encouraging to see that this virus did not seem so far more severe than seasonal flu strain.

These reassuring signs do not apply in Mexico. If the proportions are different in nature from those of rich countries: 42 died on 1 112 cases confirmed to 8 May 2009, this is not the most worrying. The figures are unreliable, the WHO said that the recent growth is mainly due to statistical bias and not a real disease. Dr. Richard J. Webby states: "since the symptoms of influenza A are the same as those of seasonal flu, this could simply reflect lethality hundreds of thousands of infected people who have escaped the Official Mexican health". The actual number of deaths is probably larger and 101 other deaths are considered suspect. In Mexico, people affected are not necessarily part of the population most vulnerable, this qualitative element suggests a fatality profile different from that of rich countries.

If, for 40 years, no rich country has experienced an epidemic of flu much more lethal than seasonal, this is different for the less medicalised. The epidemic of Madagascar in 2002 was 754 deaths in 30 304 reported cases. Some regions of the world have no way to avoid an epidemic if it occurs, and effectively treat its people. This is the case of Somalia, its medical centers are destroyed by civil war. The adviser to the Minister of Health said that "We are not prepared to manage swine influenza ... God help us if the flu happens to date.

With regard to the total assessment of the case, Anne Schuchat of the CDC evaluates the 22 May to 1 20 the number of confirmed cases in the United States, 20 patients for each confirmed case. "In fact, a minority of cases are counted individually. Some media reported scores of around one million cases in this country.

This report is only valid for the United States of America and may vary greatly from one country to another (depending on how the tests are conducted. Thus, Professor John Oxford of the United Kingdom, for its part in 1 in 300 confirmed cases there.

Hypothesis concerning the origin of the disease
One of the largest pig farms, located in La Gloria in the region of Perote in the state of Veracruz, Mexico, is suspected by the local people badly affected and the surrounding areas, to be the origin of the pandemic.

In a first time, Mexican authorities believe to have found patient zero: Edgar Hernandez, sick in late March of a proven case of H1N1. However, April 30, the control center in Atlanta published a report on another case in Mexico who developed the virus mid-March, 15 days before Hernandez.

In March and April 2009, over 2 200 cases of influenza on individuals have been identified in Mexico and the Southwest United States, causing more than 19 confirmed dead in Mexico for the most part, and central Mexico. Some cases in Mexico and the United States has been confirmed by WHO as a new strain of H1N1.

On 24 April 2009, schools (at pre-school to university) were closed temporarily by the Government of Mexico City and the State of Mexico with the support of the Secretaria de Educacion Publica (SEP) to prevent the disease from spreading to other regions.

At 25 April 2009, people have been affected in the State of San Luis Potosí, the Hidalgo, Queretaro, the Federal District and Mexico State as well as Texas and California.

Some experts as the microbiologist in chief of the Department of Microbiology at Mount Sinai Hospital in Toronto, Dr. Donald Low, confirm [citation needed] the relationship between the virus of influenza A (H1N1) and confirmed cases in Mexico.

It is recommended to strengthen the population health precautions.

The Ministry of Health has launched an alert, and decreed the suspension of activities of schools both public and private.

The virus causing influenza A is not transmitted by consuming meat from infected pigs, because the virus is not resistant to high temperatures used for cooking.

The Mexican authorities have closed schools, museums and theaters, football matches do not receive the public and distributed masks. The stations broadcast messages of prevention.

The french ministry of Health has set up a crisis unit to advise the French resident in Mexico and passengers; a crisis psychiatric sent to the travelers from across the Atlantic has been set up to 'Orly airport. Information is also available on the websites of the Ministry of Health and Sports, the World Health Organization and the French Embassy in Mexico.

On 6 May 2009, the CDC announced the manufacture and distribution of a new test fastest alone explains the explosion of confirmed cases, mostly in the United States, a few days later.

Genetic characteristics and effects
Dr. Anne Schuchat (Center for control and prevention of diseases in the United States (CDC)), stated that the U.S. cases result from a virus characterized by a recombination of genetic elements from four different viruses:

* Swine flu in North America,
* Avian flu in North America,
* A human influenza type A subtype H1N1, and
* A swine flu virus typically found in Europe and Asia;

is "a unique blend and never met or the United States or elsewhere, gene sequences". This new strain might result from an infection in a sick person.

For two isolates, the complete genomic sequences have been obtained [ref. necessary]. These are used by U.S. researchers to develop a vaccine. Dr. A. Schuchat said that the virus is resistant to amantadine and rimantadine, but is sensitive to oseltamivir (Tamiflu) and zanamivir (Relenza).
Based on data available on 1 May 2009, A. Schuchat believed in a home contaminated by each patient on average about a quarter of other family members, as in the case of seasonal influenza and at the same time, Dr. Nancy Cox (head of department of CDC flu ) are not found in the virus' virulence markers that were observed in the virus in 1918, but remained cautious because of the dangerousness of influenza virus remains poorly understood.

Preliminary genetic characterization showed that the gene for hemagglutinin (HA) is similar to that of influenza virus fever in the United States since 1999, but the genes for neuraminidase (NA) and the matrix protein ( M) similar to the variants that are found in isolates of swine influenza in Europe.

Patients with influenza A (H1N1) have exactly the same symptoms as influenza usual (seasonal):

* The incubation period (the period between contact with the virus and the onset of symptoms) is 24 to 48 hours,
* The patient's temperature rises, up to 41 ° C,
* The patient experiences muscle pain (ache), mainly in the back,
* The patient is extremely weak
* The patient feels pain in the throat and possibly headaches,
* The patient coughing and deep rather dry
* The patient has trouble breathing sometimes important and a strong nose,
* The patient has a sudden loss of appetite,
* And in some cases vomiting and diarrhea

The evolution of H1N1 influenza A depends on the individuals concerned. It is not possible to predict the evolution of this virus with certainty. Usually, influenza A H1N1 evolves favorably toward healing in a week.

Read also Swine Influenza