Use of Antiviral Drugs in The 2009 H1n1 Pandemic

As of the 11th June, 2009, World Health Organisation (WHO) declared the outbreak of the H1N1 flu strain (Colloquially known as ‘Swine Flu’) to be at Level 6, pandemic stage. This declaration follows an epidemic situation which was first identified in Mexico. It was thought to have started in Mexico in January of 2009, but now speculation has arose and it is now thought by some scientists that the flu started and developed in Asia before being transferred to North America, but the theories made do not currently have enough evidence to support them. Since the spread of the flu worldwide, countries have put their pandemic plans into action. For developed countries this included stockpiling a large amount of Antiviral drugs.

 The purpose of Antiviral drugs is to work directly on viruses, by trying to stop the virus from multiplying. WHO has identified two drugs to be used which work effectively in the battle against this particular flu strain. Oseltamivir (Tamiflu) and Zanamivir (Relenza) are the two identified Antiviral drugs effective in treating the treatments of swine flu.  The drugs help to; reduce length of illness on average by one day, relieve some of the symptoms, reduce the risk of contracting more serious illnesses. They are considered to be effective and viable swine flu treatments. During the first months of the developing situation, the drugs were being administered to patients who had been diagnosed with the H1N1 Flu. People who were coming into close contact on a regular basis with the infected individual were also given the drugs.

The drugs have been designed to work effectively against Fly types A and B. The H1N1 strain is a subtype of influenzavirus A. The genetic elements of the strain can be split into four parts; North American swine influenza, North American avian influenza, human influenza and Eurasian swine influenza. This is an unusual mix of the four flu viruses. It appears to be the result of an antigenic shift between swine and human influenza viruses. Both drugs have been approved to be used by adults and children over the age of seven.

Oseltamivir is one of the official recognised Antiviral drugs used to treat the symptoms of the new flu strain. The drug can be used to treat influenzavirus A and influenzavirus B. The drug becomes active as it passes through the liver. It was developed by Gilead Sciences and has been marketed by Roche under the trade name Tamiflu.

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Oseltamivir can be taken either orally via tablets, or a suspension. On the surface of the influenza virus is neuraminidase, this is a helping chemical which chemically creates a pathway between cells in the human body to act as a pathway, a way the virus can spread across the body. Tamiflu works by binding to the neuraminidase surface; it then inhibits the new viral particles chemical ability to escape from the infected cell, in theory dissolving the pathway. Therefore the virus spreads to a smaller amount of cells, therefore the immune system has a better chance of killing the influenza virus. Like many other drugs Oseltamivir provides some side effects in various people who take the Antiviral drugs, these include; nausea, vomiting, diarrhoea, abdominal pain and headaches. Concern has been raised due to the possible psychological and neuropsychiatric side effects of the drug such as self harming. These conditions are more likely to occur in children than in adults, the focal point of the concern has been based on teenagers using the drug. Japan consumes Oseltamivir more than any other county; they use 60% of the world’s production of the drug. Japans health experts have looked closely at this drug and in March 2007 the Ministry of Health in Japan warned against the drug being used on individuals between 10 and 19, due to the detrimental effects it can cause. The review of safety on Oseltamivir was caused by multiple Japanese individuals committing suicide. Of these people the majority age group involved was teenagers. The USA also warned about the usage of this drug, they warned that it can cause delirium and hallucinations.

Zanamivir is the other officially promoted Antiviral drug for use in treating symptoms of the new flu strain. Zanamivir was developed by the Monash University in collaboration with CSIRO and GlaxoSmithKline. Zanamivir is marketed by GlaxoSmithKline under the trade name Relenza. Zanamivir was the first ever neuraminidase inhibitor. The Antiviral drug is taken via inhalator. This is the reason that this is the Antiviral drug used by pregnant women. Though Oseltamivir is regarded as for pregnant women, there is still more of a risk involved, for that reason it is never used by pregnant women. Because Relenza is taken via inhalator the first system to be targeted by it is the respiratory system, this is the focal point of the Antiviral, and so the risk of interacting with foetal development is drastically reduced. Zanamivir just like Oseltamivir is a neuraminidase inhibitor and works the same way, but with an inhalator opposed to being taken orally.

 According to tests conducted by the Centres for Disease Control and Prevention (CDC) a United States federal agency, it has been shown that 99.6% of the 2008 seasonal H1N1 flu strain is resistant to the drug. This is the reason that Oseltamivir is not used for seasonal flu treatment. As of October 2009, WHO has announced that out of 10,000 samples of the 2009 H1N1 pandemic strain, only 39 have shown resistance to Oseltamivir. On the October 29th U.S researchers say that they have seen the first case of Tamiflu resistant flu spreading between two people. In June and July of 2009, 65 campers and staff at summer camp in North Carolina were diagnosed with H1N1, and they were treated with Oseltamivir. The other 600 campers present at the summer camp were also given the antiviral to prevent getting the illness. Two of the females who were sharing a cabin developed symptoms after receiving Tamiflu. They were found to have two viral mutations that caused the paid to be resistant to the Antiviral drug. This mutated virus was never found present in any other of the campers. It has appeared that one of the females transferred the mutated virus to her fellow cabin mate. This then suggests that the use of Oseltamivir to prevent the disease can cause resistance to H1N1. Following this and other guidance WHO suggested that the drugs should only be used in more severe cases of the flu. This is due to evidence to suggest most cases of this flu strain can be easily treated with over-the-counter medications opposed to an Antiviral drug. The WHO is now recommending only using the H1N1 vaccine, which in September was approved for use, to prevent swine flu. So for Zanamivir has shown no signs of resistance to both seasonal and swine flu.

If in the unlikely event that the H1N1 influenza strain becomes resistant to both Antiviral drugs, there is one last drug that may be of use. Peramivir is a new, experimental drug that acts as a neuraminidase inhibitor. As of October 2009, it was reported that the Antiviral Peramivir is effective in treating more serious cases of swine flu. On October 23rd 2009, the U.S Food and Drug Administration (FDA) issued an Emergency Use Authorization for Peramivir, allowing it to be used for treating the swine flu in cases where Tamiflu has shown a resistance and the method of taking Relenza has caused an issue.