Anti-viral resistance in 2009 A/H1N1 flu - historical compilation of news

[Gert van der Hoek]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Snip from weekly CDC report week 34 (August 23-29, 2009)

2009 influenza A (H1N1) viruses were tested for oseltamivir resistance by a neuraminidase inhibition assay and/or detection of genetic sequence mutation, depending on the type of specimen tested: original clinical samples were examined for a single known mutation in the virus that confers oseltamivir resistance in currently circulating seasonal influenza A (H1N1) viruses, while influenza virus isolates were tested using a neuraminidase inhibition assay that determines the presence or absence of neuraminidase inhibitor resistance, followed by the neuraminidase gene sequence analysis of resistant viruses.

The majority of 2009 influenza A (H1N1) viruses are susceptible to the neuraminidase inhibitor antiviral medication oseltamivir, however rare sporadic cases of oseltamivir resistant 2009 influenza A (H1N1) viruses have been detected worldwide, including nine cases in the United States.

All tested viruses retain their sensitivity to the other neuraminidase inhibitor zanamivir. Additional information on antiviral recommendations for treatment and chemoprophylaxis of 2009 influenza A (H1N1) infection is available at http://www.cdc.gov/h1n1flu/recommendations.htm All 2009 influenza A (H1N1) viruses tested to date are resistant to the adamantane antiviral medications, amantadine and rimantadine.

Antiviral treatment with either oseltamivir or zanamivir is recommended for all patients with confirmed, probable or suspected cases of 2009 influenza A (H1N1) virus infection who are hospitalized or who are at higher risk for seasonal influenza complications.

Eight of the nine patients had documented exposure to oseltamivir through either treatment or chemoprophylaxis, and the remaining patient is currently under investigation to determine exposure to oseltamivir. Occasional development of oseltamivir resistance during treatment or prophylaxis is not unexpected.

Enhanced surveillance is expected to detect additional cases of oseltamivir resistant 2009 influenza A (H1N1) viruses and such cases will be investigated to assess the spread of resistant strains in the community. To prevent the spread of antiviral resistant virus strains, CDC reminds clinicians and the public of the need to continue hand and cough hygiene measures for the duration of any symptoms of influenza. (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5832a3.htm)

http://www.cdc.gov/flu/weekly/

credits Momcares

[Gert van der Hoek]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Google translated

Hong Kong's Tamiflu-resistant virus to reproduce

(Star Island) September 9, 2009 Wednesday, 21:11

Department of Health, Public Health Laboratory Service, today found an H1N1 flu virus, oseltamivir (ie, Tamiflu) resistance appears.

This is the third time with H1N1 influenza virus appears resistant to the Tamiflu, is the second local cases.

The strains of virus on zanamivir (Relenza that is) does not appear resistant.

The virus obtained from a sample Saba-year-old man was separated, he had not previously had taken Tamiflu.

The patient report full report on the flu-like symptoms, the designated flu clinic in the July 30 confirmed that the patient's respiratory sample yielded positive H1N1 influenza virus.

http://hk.news.yahoo.com/article/090909/3/e4y6.html&sl=zh-CN&tl=en&history_state0=

[Gert van der Hoek]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Health Officials Find Resistant Strain of Swine Flu

Reported: 13:20 PM - Sep/10/09


(IsraelNN.com)
Health Ministry officials have discovered a strain of swine flu in Israel that is resistant to Tamiflu, a drug that has until now been used effectively in preventing the spread of the virus. The strain was discovered in a patient who had been diagnosed with the H1N1 virus but was later thought cured after being treated with, among other things, Tamiflu.

Strains of swine flu resistant to Tamiflu have been found in other countries as well.

The Health Ministry said Thursday that it was not changing any of its instructions to patients and doctors on how to treat swine flu.

http://www.israelnationalnews.com/News/Flash.aspx/170886

[kiwibird]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Did drug-resistant swine flu spread between teens?
By MIKE STOBBE
Associated Press
2009-09-11 12:04 AM
Fonts Size: A+
E-Mail This Email
Printer-Friendly Printer
U.S. health officials are reporting what may be the first instance of a Tamiflu-resistant swine flu virus spreading from one person to another.

It happened in July at a camp in western North Carolina, where two teenage girls _ cabin mates _ were diagnosed with the same drug-resistant strain of swine flu.

Tamiflu is one of two flu medicines that help against swine flu, and health officials have been closely watching for signs that the virus is mutating, making the drugs ineffective.

The Centers for Disease Control and Prevention is aware of nine U.S. cases of Tamiflu-resistance since swine flu first appeared in April, but all the others were single cases. In this instance, there seemed to be a spread.

"That was the concerning thing about these cases," said Dr. Zack Moore, a respiratory disease epidemiologist for the North Carolina Department of Health and Human Services.

The virus may have spread from one girl to the other, or it's possible that the girls got it from another camper. It's also possible that they each developed a resistant strain independently, but that's unlikely, Moore added.

Both girls had been given Tamiflu before they got sick _ as a preventive measure _ after an outbreak of swine flu at the camp. They were among more than 600 campers and camp staff treated.

That may have been part of the problem: Overuse of medicines can contribute to viruses becoming drug resistant.

The CDC this week issued revised guidance advising against giving flu drugs to prevent illness in most healthy people, even if they may have been exposed to an infected person.

The CDC recommends fast treatment with Tamiflu or Relenza for anyone hospitalized with a flu-like illness. They also advise prompt treatment at the first sign of symptoms for those at high risk for serious complications, including pregnant women, children younger than 5, and people with certain chronic conditions like asthma and heart disease.

"Tamiflu is still considered effective. This is just a reminder we need to be cautious with these drugs," Moore said.

The North Carolina cases are reported in Thursday's issue of a CDC publication, Morbidity and Mortality Weekly Report.

___http://www.etaiwannews.com/etn/news_content.php?id=1054148&lang=eng_news&cate_img =316.jpg&cate_rss=news_Health

[Gert van der Hoek]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

September 9, 2009

WHO: H1N1 Tamiflu Resistance, number of known cases rises to 21

http://bit.ly/19kZTq

[sharon sanders]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Thanks Dutchy.

[Niko]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

Tamiflu resistance reported in 23 patients: Roche

Fri Sep 11, 2009 3:05pm EDT
By Julie Steenhuysen

CHICAGO (Reuters) - Roche Holding AG said on Friday there have been just 23 reported cases in which H1N1 swine flu has resisted the effects of antiviral drug Tamiflu.

Tamiflu, made by Roche and Gilead Sciences Inc, is one of two drugs shown to work well against H1N1 swine flu.

Dr. David Reddy, who leads Roche's pandemic task force, told reporters the number was in line with what the company had observed in its own clinical trials.

"As we see more of the drug used, we will see more of these isolated cases over time," Reddy said in a conference call.

He said there have been no significant clusters of resistance, and no signs that a resistant strain is spreading in any one community.

About 13 of the cases of resistance occurred in people who had been exposed to the new H1N1 virus and were given a low dose of the drug to prevent infection.

In such cases, Reddy said doctors should watch patients closely for signs of illness and consider switching to a stronger, treatment-level dose if a patient actually becomes sick.

Resistance to antiviral drugs has been a concern.

Last year, the seasonal H1N1 flu virus -- a different strain from H1N1 swine flu -- developed resistance against Tamiflu in the United States and many other countries.

Flu viruses are prone to mutation and experts are not surprised that they would evolve resistance, just as bacteria develop resistance to antibiotics.
Tamiflu, known generically as oseltamivir, and GlaxoSmithKline and Biota's Relenza, known generically as zanamivir, not only fight flu. They can prevent infection if given soon enough.

Reddy said Roche has been gearing up its capacity and can now deliver 33 million doses of Tamiflu per month. He said the company is also conducting 13 laboratory studies and 30 studies of the drug.

"Most of our activities are focused around vulnerable populations," including patients with compromised immune systems, severely ill and obese patients, Reddy said.

The company is working with the U.S. Food and Drug Administration on ways to make the drug easier for children to take, including putting it in small capsules, and developing instructions on how to mix Tamiflu with food for children who cannot swallow capsules.

The H1N1 virus has killed at least 3,205 people worldwide since emerging last April in North America and is the predominant flu virus circulating in both hemispheres, according to the World Health Organization's latest weekly update issued separately on Friday.

The U.S. Centers for Disease Control and Prevention said this week that most swine flu patients do not need antivirals, but those who do -- especially those who are having trouble breathing -- should be treated quickly.

H1N1 usually causes mild symptoms, but pregnant women and people with conditions such as asthma are at higher risk.

(Editing by Maggie Fox and Todd Eastham)

http://www.reuters.com/article/GCA-SwineFlu/idUSTRE58A54T20090911

[Gert van der Hoek]

Re: Tamiflu resistance in A/H1N1 flu - historical compilation of news

9 September 2009

Detection of human swine influenza virus resistant to Tamiflu

A spokesman for the Department of Health (DH) said the department's Public Health Laboratory Services Branch (PHLSB) today (September 9) detected a strain of human swine influenza (HSI) virus which was resistant to oseltamivir (Tamiflu).

The virus was identified during PHLSB's sensitivity test of HSI virus to oseltamivir and zanamivir, the spokesman said.

"The is the third time Tamiflu resistance in HSI virus found in Hong Kong and this is the second local case.

"Tests showed that this strain is sensitive to zanamivir (Relenza)," he said.

The virus was isolated from the specimen taken from a 38-year-old man who had no history of taking Tamiflu.

The patient developed flu-like symptoms on July 26 and his respiratory specimen taken at a Designated Flu Clinic was tested positive to HSI on July 30.

Investigation revealed that four other family members also suffered from laboratory confirmed HSI including his wife, son, and two younger brothers sequentially at end of July. One of his younger brothers, aged 32, who had onset of flu like symptoms on July 23 had received a full course of Tamiflu treatment.

Except for this patient, all available isolates from other members of the family, including the specimen taken from the younger brother before he received Tamiflu treatment, were tested to be sensitive to Tamiflu.

The patient and all other affected members had mild illnesses and recovered.

The spokesman said that there was no evidence of further transmission of Tamiflu-resistant HSI from the patient.

The spokesman said that PHLSB conducted routine sensitivity tests on specimens taken from confirmed HSI patients.

So far more than 3000 HSI samples had been tested for sensitivity in Hong Kong.

The case will be reported to the World Health Organization (WHO), the spokesman said.

He reiterated that Hong Kong had an intensive influenza surveillance system on antiviral resistant influenza viruses.

"We will closely liaise with WHO and overseas health authorities and monitor the global development of antiviral resistant HSI virus," he said.

Ends/Wednesday, September 9, 2009

http://www.chp.gov.hk/content.asp?lang=en&info_id=18618&id=116

thanks to CPB

[Treyfish]

Tamiflu resistance in A/H1N1 flu - historical compilation of news

CHQR Newsroom
9/15/2009

Alberta Health Services is reporting Canada's second drug-resistant H1N1 case.
Dr. Gerry Predy, Alberta's senior medical officer of health, says the case is significant because the drug oseltamivir, or Tamiflu, is the medication that is most commonly used to treat influenza around the world.
He says any resistance to medication is important because it could possibly lead to further cases of resistant disease and potentially affect how a disease spreads.
Predy says an investigation into the case is underway to determine if the drug-resistant organism was present at the start of patient's illness or if it developed during treatment.
Other isolated cases of drug resistant H1N1 flu have been reported around the world, including an earlier case involving a 60-year-old man from Quebec who was given the drug when he was exposed to H1N1 because his son was ill.
Predy says the Alberta patient was not hospitalized and is recovering. http://www.am770chqr.com/News/Local/...spx?ID=1140102

[Treyfish]

Tamiflu resistance in A/H1N1 flu - historical compilation of news




By Michelle Fay Cortez
Sept. 15
(Bloomberg) -- Swine flu that can resist treatment with Roche Holding AG?s Tamiflu is also harder to spread to other people, according to World Health Organization officials.
Almost two dozen people have developed swine flu infections that don?t respond to Tamiflu, a mainstay of therapy for the outbreak that began in April. The genetic mutation that helps the virus evade the drug also thwarts its transmission, so the infection isn?t passed on to other patients, said David Mercer, acting head of the communicable diseases unit of the WHO?s European region.
?It?s a very specific genetic mutation that causes resistance and reduces the transmissibility of the virus, so it?s not infectious,? Mercer said in an interview in Copenhagen, where the WHO?s European governing body met this week.
The findings may reassure public health officials worried that overuse of Tamiflu would render impotent one of the key weapons against the pandemic virus. Some countries, including the U.K., took an aggressive approach to controlling the outbreak when it first arrived at the end of April, giving Tamiflu to people who had come into contact with pandemic flu patients to slow the spread of the disease.
For patients with seasonal influenza that doesn?t respond to Tamiflu, the only treatment option is GlaxoSmithKline Plc?s inhaled drug Relenza. Reducing therapies for the pandemic outbreak, caused by a novel combination of avian, swine and human influenza, could be disastrous if the virus, formally known as H1N1, turns more deadly, Mercer said. Flu patients who are otherwise healthy and without serious complications shouldn?t get Tamiflu, he said.
Viruses Change
?Healthy patients with uncomplicated illness don?t need antivirals,? Mercer said. ?Viruses do change and evolution is unpredictable. Seasonal influenza is almost entirely resistant. Overuse of Tamiflu could result in the same thing? for swine flu, he said.
The WHO has been too firm on its advice to not treat patients with uncomplicated infections, said Liam Donaldson, England?s chief medical officer. About 40 percent of deaths occur among previously healthy people, and treatment is most effective when given early, before it?s clear whether the infection is complicated, he said.
?Some people will die? if left untreated, Donaldson said. ?To regard them as inevitable statistical occurrences doesn?t go down well. We have these antivirals and we know they can have an impact.?

52,000 Cases

There have been more than 52,000 confirmed cases across 48 countries in Europe, including at least 140 deaths, Mercer said. Almost 90 percent of the deaths occurred in the U.K., Spain and Israel, he said.
There have been 23 cases of resistance developing to Tamiflu, Mercer said. Twelve of them were healthy people who had encountered swine flu patients, and were given Tamiflu in an effort to prevent the infection from taking hold, he said. Four or five others were healthy patients who had mild infections.
?The good news is that the resistant strains haven?t been transmissible to others,? Mercer said. ?It?s not infecting anyone else.?
To contact the reporter on this story: Michelle Fay Cortez in London at mcortez@bloomberg.net
Last Updated: September 15, 2009 11:00 EDT

http://www.bloomberg.com/apps/news?pid=20601082&sid=aG.qKHeqAsi4

[Pathfinder]

Re: Alberta records case of drug-resistant H1N1

Drug-resistant H1N1 case not 'alarming'
Few sufferers need treatment for fluJodie Sinnema, edmontonjournal.com:
Wednesday, September 16, 2009 6:47 AM

EDMONTON ? Alberta's first drug-resistant case of the H1N1 virus is concerning but not unexpected, and won't change how the province rolls out its vaccination campaign this fall.

"It's always a concern that there's resistance," said Dr. Gerry Predy, senior medical officer of health for Alberta Health Services. "One isolated case is probably not that significant, but it does then mean we have to do some investigation around this case, just to make sure that it is isolated."

The woman infected with H1N1 did not have to be hospitalized but was being treated with oseltamivir, also called Tamiflu, the most commonly used treatment for influenza in the world. Most people who get the H1N1 flu virus will only have a mild form of the illness and not need any medication, but people who have more severe cases, or who have other health problems that put them at risk for infection, are typically given Tamiflu to treat or prevent an infection.

A sample from the woman was sent to Winnipeg in August, and the lab confirmed in the last few days that her flu strain was drug-resistant. The woman is no longer sick, but an investigation is determining if any of her family or friends became sick with the mutated and resistant strain.

Investigators will also do tests to see if the drug-resistant organism was present at the start of the woman's illness or developed during treatment.

"I don't think it's, at this point, anything people should be alarmed about," Predy said.

But he said results from the investigation could refine guidelines on how people with severe illness should be treated. If someone with the flu is hospitalized and becomes resistant to the medicine, the infection could become more difficult to control and could remain infectious for a longer time, putting more people at risk, Predy said.

One other antiviral works against H1N1 and is available in Alberta, he said.

"However, it is important because oseltamivir is one of our main tools to deal with a pandemic," he said. "Because most people with H1N1 develop mild illness and they won't be treated with antivirals, it's really not significant to the majority of people getting infected with H1N1."

Typically, between 0.5 and four per cent of people treated for flu become drug-resistant, Predy said. With only one other drug-resistant case so far in Canada--that of a 60-year-old Quebec man--the resistance rate with this flu strain is at the lower end of that spectrum. Of the approximately 70 Alberta samples sent to Winnipeg for drug-resistance testing, only one out of the 50 received back has been positive.

Other isolated drug-resistant cases have been reported around the world and are being monitored by the World Health Organization.

http://www.globaltvedmonton.com/health/Drug+related+H1N1+case+alarming/1995963/story.html

[Pathfinder]

Tamiflu resistance in A/H1N1 flu - historical compilation of news

ICAAC: Three-Drug Cocktail Aimed at Resistant Flu

By Michael Smith, North American Correspondent, MedPage Today

Published: September 16, 2009

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco.


SAN FRANCISCO -- A three-drug combination aimed at flu appears to overcome drug resistance -- at least in the test tube.

The three drugs -- amantadine (Symmetrel), ribavirin, and oseltamivir (Tamiflu) -- display an unexpected synergy when used together, according to Mark Prichard, PhD, of the University of Alabama Birmingham.

In a series of laboratory experiments, the triple-drug combination -- dubbed TCAD -- successfully inhibited both amantadine-resistant and oseltamivir-resistant viruses, Prichard said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

One unexpected finding, Prichard said, was that amantadine contributed to the effect even when used against virus strains resistant to the drug.Action Points

The synergy was seen in both seasonal and pandemic H1N1 strains, he said, as well as H3N2 seasonal flu and the highly pathogenic H5N1 avian influenza strain.

The use of triple combinations is common in other diseases, according to Karen Bush, PhD, of Indiana University in Bloomington. Bush, a member of the meeting's program committee, was not part of the study.

For instance, she said, both HIV and Helicobacter pylori are commonly treated with three drugs, usually from different classes, with the hope that a three-pronged attack will be more effective than single or double dosing.

When such drugs are taken over a long period of time -- as in HIV infection -- there is a potential to develop a virus that is highly resistant to several types of drugs, she said.

But in the case of flu, the TCAD combination would probably be only used in the setting of acute illness and only for a few days, which should minimize that risk.

"I would certainly not use it prophylactically," Bush said.

Indeed, Prichard said, the three drugs attack different targets, which should increase the genetic barriers to resistance.

Amantadine blocks the influenza M2 protein, which is involved in fusion of the virus to the cell, while oseltamivir blocks the enzyme neuraminidase, which plays a role in letting new viral particles escape from an infected cell.

Ribavirin -- not usually used against the flu -- interferes with viral replication, Prichard said.

Although the data are derived so far only from in vitro testing, the researchers do not expect any safety issues, according to co-author Amy Patick, PhD, of Adamas Pharmaceuticals, which is developing the combination.

All three drugs are known to be very safe, and because they have different mechanisms of action and are cleared using different pathways, there should be few interactions, she told reporters.

The company is currently performing animal experiments, and is enrolling 250 volunteers in South America -- still in its flu season -- for a clinical trial, she said.

The study was supported by Adamas Pharmaceuticals, which is developing the compound.

Prichard did not report any conflicts.


Primary source: Interscience Conference on Antimicrobial Agents and Chemotherapy
Source reference:
Nguyen J, et el "Triple combination of amantadine, ribavirin, and oseltamivir restores in vitro activity of antiviral drugs against resistant influenza viruses" ICAAC 2009; Abstract V-537b

http://www.medpagetoday.com/MeetingCoverage/ICAAC/15998

[TrueScotsman]

Tamiflu resistance in A/H1N1 flu - historical compilation of news

Source : http://www.hpa.org.uk/webw/HPAweb&HP...=1231252394302

KEY POINTS

The rates of flu-like illness and related activity have started to increase in England. The increase was mainly seen in school age children.
Hospitalisations of people with suspected pandemic flu in England have levelled overall. The majority of cases continue to be mild.
Two samples from UK patients have been shown to have the genetic change associated with oseltamivir resistance. Both were from immunocompromised patients. One has been shown to be resistant, the other is undergoing further tests to confirm resistance. Globally over 10,000 specimens have been tested and 23 have been shown to be resistant to oseltamivir.
Interpretation of data to produce estimates on the number of new cases continues to be subject to a considerable amount of uncertainty. HPA modelling gives an estimate of 5,000 new cases in England last week (range 3,000 to 11,000).
This estimate incorporates data from National Pandemic Flu Service and GP consultations.

VIRAL CHARACTERISTICS

The Health Protection Agency has reported to the World Health Organization (WHO) the identification in the UK of a pandemic H1N1 2009 flu virus resistant to the antiviral oseltamivir (Tamilflu&#174.

The resistant virus was identified in an immuno-compromised patient. The virus has a genetic change, H274Y in the N1 gene and is resistant to oseltamivir but retains susceptibility to the antiviral zanamivir (Relenza&#174.

Preliminary test results have also shown that a second virus (in a separate immuno-compromised patient) has the genetic change. We will be able to confirm if this virus is resistant at the end of the week.

There is no evidence of onward transmission of the resistant viruses.

This is not an unexpected development. If the second sample is confirmed, then these two samples are among a small number of resistant pandemic H1N1 2009 flu viruses to have already been identified worldwide through enhanced surveillance during the current pandemic. To date the manufacturers of oseltamivir (Roche) have reported 23 cases globally. Based on current information, these isolates appear to be sporadic and at this time there is no evidence of widespread antiviral resistance among pandemic H1N1 2009 flu viruses.

Testing carried out by the HPA indicates that both patients were initially infected with oseltamivir-susceptible virus, with resistance to the drug developing during their treatment. The emergence of antiviral drug resistant flu viruses during treatment has been reported in the past and its link to immuno-compromised patients is well established.

In a healthy individual the body's immune system would ordinarily effectively eliminate any virus. However, with immuno-compromised individuals, their immune response is affected and they continue to shed flu virus for prolonged periods.

The one, possibly two, UK cases were identified through testing carried out on flu virus samples received at the Agency's Centre for Infections. We are confident that these surveillance measures will enable us to identify any further resistant isolates.

To date (as of 16 September 2009) 913 viruses have been analysed by the Centre for Infections for the genetic marker commonly associated with resistance to oseltamivir in seasonal H1N1 flu (H274Y). These are the only two viruses found to carry this marker in the UK. In addition, 253 specimens have been fully tested for susceptibility; all, apart from one, were found to be sensitive to both oseltamivir and zanamivir.

The Agency is continually assessing its advice to government on health protection policies such as antiviral use. Currently there is no requirement to change existing guidance.

SEVERITY

Disease severity continues to be monitored. The disease is generally mild in most people so far, but is proving severe in a small minority of cases.

Swine flu hospitalisations in England: 143 patients (currently hospitalised as of 8am on 16 September).

Deaths - the number of deaths related to swine flu in England is 67 (This figure represents the number of deaths in individuals with swine flu but does not represent the number of deaths that can be attributed to swine flu).

[Gert van der Hoek]

WHO: Certain H1N1 cases may predict antiviral resistance

Early use of antivirals key in H1N1 flu: WHO

Fri Sep 25, 2009

GENEVA (Reuters) - Early use of antivirals is effective in treating H1N1 flu and health authorities must be vigilant for signs of drug resistance, the World Health Organisation said on Friday.

Drug-resistant pandemic flu viruses have appeared infrequently so far and there is no evidence they are spreading, but further cases are likely, the WHO said on its website.

Growing international experience showed the importance of the early use of oseltamivir, manufactured as Tamiflu by Roche Holding and Gilead Sciences, or zanamivir, an inhaled medicine produced as Relenza by GlaxoSmithKline in swine flu cases," the WHO said.

"The experience of clinicians, including those who have treated severe cases of pandemic influenza, and national authorities, suggests that prompt administration of these drugs following symptom onset reduces the risk of complications and can also improve clinical outcome in patients with severe disease," the Geneva-based U.N. agency said.

"This experience further underscores the need to protect the effectiveness of these drugs by minimizing the occurrence and impact of drug resistance," it said.

Most people who contract pandemic influenza suffer only mild symptoms before recovery without treatment, but children, pregnant women and those with some existing health conditions are vulnerable to a more severe attack or even death.

The WHO, which declared H1N1 a global pandemic in June, says one third of the world's population of nearly seven billion people could catch it.

The risk of resistance is higher in patients who suffer from weak immune systems and have already been treated with oseltamivir, it said.

It is also high in people who are treated with the antivirals as a prophylactic -- as a precaution after exposure to someone with influenza, but nevertheless develop the disease.

In such cases medical staff should investigate whether resistance has developed and take precautions to prevent the spread of a resistant virus, it warned.

Health authorities should also investigate whether a drug-resistant virus is spreading through communities from person to person.

The WHO repeated guidance that it did not recommend taking antivirals as a prophylactic. People exposed to pandemic flu victims should be monitored closely and treated promptly with antivirals if symptoms develop, it said.

Global monitoring has detected 28 resistant viruses so far. In each case the viruses were resistant to treatment with oseltamivir but not zanamivir, which should be used to help patients suffering severe illness from an oseltamivir-resistant virus, it said.

(For the WHO note go to link.reuters.com/cad68d)

http://www.reuters.com/article/swineFlu/idUSTRE58O29O20090925?feedType=RSS&feedName=swineFlu&virtualBrandChannel=10521

[Francoise Ramona]

Re: 1,000 Members!!!

Grippe A/H1N1: des cas isol?s de r?sistance aux antiviraux (OMS)

Gen?ve (awp/ats) - Des cas isol?s de r?sistance aux m?dicaments antiviraux contre la grippe A/H1N1, tels que le Tamiflu, ont ?t? d?tect?s, a affirm? vendredi l'OMS. D'autres cas pourraient appara?tre avec l'usage plus fr?quent des antiviraux, pr?vient l'agence de l'ONU.
"Les cas de virus r?sistants ? l'oseltamivir sont sporadiques et peu fr?quents. Il n'y a pas de preuve qu'un virus r?sistant de la grippe A(H1N1) circule dans le monde et se transmet de personne ? personne", a d?clar? l'Organisation mondiale de la sant? (OMS).
Jusqu'ici, 28 cas de virus r?sistants ? l'oseltamivir sur plus de dix mille sp?cimens test?s ont ?t? recens?s dans le monde. Les risques de r?sistance sont plus ?lev?s parmi les malades dont les syst?mes immunitaires sont affaiblis et qui ont une maladie prolong?e, pr?cise l'OMS.
Le risque est consid?r? aussi plus ?lev? pour les personnes qui ont re?u de l'oseltamivir afin de pr?venir l'infection par une autre personne atteinte de la grippe et qui d?veloppent ensuite la maladie en d?pit des m?dicaments, ajoute l'organisation. L'utilisation du zanamivir est une solution de rechange en cas de r?sistance ? l'oseltamivir.
L'OMS rappelle qu'un traitement rapide avec des m?dicaments antiviraux est essentiel d?s que les sympt?mes se d?veloppent, notamment chez les patients comportant des risques de complication. Par contre, elle ne conseille pas l'utilisation des antiviraux comme moyen pr?ventif, m?me pour les personnes ayant ?t? en contact avec un malade.
Les experts de l'ONU pr?cisent que rien ne vient ?tayer la th?se selon laquelle des virus r?sistants ? l'oseltamivir sont plus dangereux. Les patients infect?s par un virus A(H1N1) r?sistant n'ont pas souffert de sympt?mes plus graves.
N?anmoins, comme l'usage des antiviraux va se r?pandre avec la propagation de la pand?mie, l'OMS s'attend ? ce que davantage de cas de r?sistance apparaissent. Elle recommande aux laboratoires et h?pitaux de renforcer les mesures d'isolement et de contr?le en cas de d?couverte de cas de r?sistance pour ?viter que le virus r?sistant se transmette.
ats/rp
(AWP/25 septembre 2009 12h30)