The Novel H1N1 Flu Pandemic: Are We Prepared?
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The Novel H1N1 Flu Pandemic: Are we prepared? The Novel H1N1 Flu Pandemic: Are we prepared? Robert C. A. Yang, PhD Abstract Key words: Swine flu, novel influenza A (H1N1) virus, The 2009 swine flu pandemic is caused 2009 flu pandemic, gene reassortment, by a novel influenza A (H1N1) virus. seasonal flu epidemic, flu pandemic Phylogenetic study reveals that this timeline virus possesses genes derived from viruses of swine, avian and human Initial outbreaks origins through several reassortments. Towards mid-April this year (2009) This virus is capable of spreading from the swine flu that broke out in Mexico person to person readily resulting in a causing numerous cases of infection worldwide pandemic flu as of June 11, and claiming many lives has caught 2009. The flu pandemic timeline for the the international health authorities by past century demonstrates that all the surprise. Why not the HN1 avian flu causative viruses for the pandemics or the SARS-like epidemic? The whole as well as the seasonal epidemics are world has been geared to face any attributed to the type A influenza. The challenges from the two for many years, novel H1N1 virus has established itself since the major outbreaks of the HN1 rapidly as a dominant influenza A strain avian flu with human casualties as of in most parts of the world. So far, most, if late December 200 and ongoing to not all, of the pandemic patients suffers date. It is noted that after HN1 emerged a mild illness. The majority (90%) of the widely in Asia in 200, killing about world's population lives in the northern 0-0 percent of the humans infected hemisphere who is as yet to experience by the virus, many countries took steps the first fall and winter seasons, when it to prevent a similar crisis. SARS was is most prone for flu outbreaks due to the rampant for approximately six months cold and dry weather. A second wave of between February and July 200 with a the pandemic attacks seems inevitable. case fatality rate or CFR of approximately 藥學雜誌 100期 THE JOURNAL OF TAIWAN PHARMACY 第25卷 第 3 期 臨 床 藥 學 10%. It even spread from Asia to the North America in a cluster. The current swine flu epidemic spread quickly across the borders to the immediate neighbor, the U.S.A. and even further north to Canada. The panic was understandably Fig. 1. Pandemic Influenza Phases reflected by the sharp world wide plummeting of the stock market during Phase criteria: In addition to the one week in late April. The rest of the criteria defined in Phase , the same world has not been left unscathed. As virus has caused sustained community- level outbreaks in at least one other the time goes by the H1N1 virus has country in another WHO region 1 invaded other continents beyond the (Courtesy of the WHO). North America, such as South America, T h e W H O h a s s u b s e q u e n t l y Europe, Asia, Australia and Africa. admitted on July 1 that the pandemic The number of countries affected has is unstoppable. As of this date, the increased rapidly. By July 21, the WHO WHO will give up all reports on lab- (World Health Organization) reported confirmed total cases, whilst fatal cases 1,1 laboratory-confirmed cases and due to the novel H1N1 should be lab- 1 deaths (CFR at 0. %) worldwide confirmed. The argument is that it is from 1 affected countries. A month either wasteful or pointless to carry out prior, all 0 states in the United States, costly diagnosis, as the new flu has the District of Columbia, Puerto Rico, become so rampant in most, if not all, and the U.S. Virgin Islands had reported communities and countries. Because it novel H1N1 infection. is a mild flu, most people have chosen to stay home until self-recovery. So, the WHO declares: 2009 Flu pandemic reporting of totals has become much too On June 11th, the WHO announced that inaccurate and actually meaningless. its alert level for H1N1 influenza should In mid-July, experts believe that in the be raised to phase - see the following USA alone there might have been more chart. A global pandemic is officially than a million cases. However, the WHO under way. This is just to signal the and the CDC (Centers for Disease beginning of the so-called first summer Control and Prevention, USA) stress on wave of the pandemic (see Fig. 1. the significance of reports for unusual Pandemic Influenza Phases ). clusters of the new H1N1 virus and the The Novel H1N1 Flu Pandemic: Are we prepared? related severe cases by the national Viral origins health authorities. In particular, any drug- P h y l o g e n e t i c a n a l y s i s t h r o u g h resistant cases should be reported and international collaboration has produced the strains involved should be shared insights in the origins of the novel 2009 among the international flu scientists. As flu. Obviously it is a human flu in that from now both the WHO and the CDC it is spreading from person to person. consider that to estimate the spread But unambiguously this virus has its of the “unstoppable” virus through immediate origins in pigs. Specifically computer-modeling is more sensible it is the product of reassortment events than counting the total cases.1,2 between at least two swine flu variants. Moreover, one of the variants has some Clinical symptoms genes linked to an avian virus and A recent study carried out by the CDC human HN2 virus (one of the circulating has shown that sufferers of the new seasonal flu agents to date). In short, the H1N1 tend to come down with fever novel 2009 swine flu virus is an influenza (9%) and cough (%). Besides the two type-A virus consisting of genes derived most common symptoms, the following from viruses of swine, avian and human signs are also seen: as shortness origins through several reassortments,. of breath (%), fatigue/weakness Evidence from multiple outbreak sites (0%), chills (%), myalgias (%), demonstrates that the H1N1 pandemic rhinorrhea or running nose (%), sore 2009 virus has rapidly established itself throat (1%), headache (1%), vomiting and is now the dominant influenza strain (29%), wheezing (2%), diarrhea (2%). in most parts of the world. The pandemic The manifestations and the mode of will persist in the coming months as transmission are very similar to those of the virus continues to move through susceptible populations. the seasonal influenza. Patients with at least two signs of the acute respiratory Seasonal flu epidemics illness should call their care providers Influenza epidemics recur annually promptly. The duration of illness is mostly in the cold dry winter seasons. typically - days. The infectious period A n n u a l i n f l u e n z a e p i d e m i c s a r e for a confirmed case is defined as 1 day estimated to affect -1% of the global prior to the onset of symptoms to days population. Most cases are mild, but may after onset. The CDC has noted that cause severe illness in - million people most infections continue to be mild and and around 20,000-00,000 deaths recovery is extremely quick. worldwide. In industrialized countries 藥學雜誌 100期 THE JOURNAL OF TAIWAN PHARMACY 第25卷 第 3 期 臨 床 藥 學 severe illness and deaths occur mainly to 100 million people were killed worldwide. in the high-risk populations of infants, the An estimated 00 million people, one third - elderly, and chronically ill patients. of the world's population (approximately Pandemic timeline 1. billion at the time), became infected. In the past century, Influenza A virus The estimated numbers are definitely very strains caused three major global imprecise given the fact that the influenza epidemics: the Spanish flu in 191 virus was only formally discovered in 19 (caused by influenza A virus subtype by Smith and colleagues.9 By the same H1N1), Asian flu in 19(caused by token, since no laboratory techniques influenza A virus subtype H2N2) and were available at that time for confirmation Hong Kong flu in 19-9 (caused by other than clinical manifestations, the influenza A virus subtype HN2). These gross estimated figures include both the pandemics were all caused by various pandemic and the seasonal flu sufferers. subtypes of Influenza A virus that had t was no doubt that a dreadful pandemic undergone major genetic reassortments I and for which the population did not took place globally that killed more people possess significant immunity. The overall than those (1 million, 1% of the 1. effects of these pandemics and epidemics billion of the world's population) killed in are summarized in the table below., the World War I including both military It is estimated that anywhere from 20 personnel and civilians (Table 1.). Table. 1. 20th century flu pandemics Influenza A virus People infected Deaths Case fatality Pandemic Year subtype (approx) (est.) rate (CFR) 191 flu 0. to 1 billion 191-19 H1N1 20 to 100 million >2.% pandemic (near 0%) Asian flu 19- H2N2 2 million <0.1% Hong Kong flu 19-9 HN2 1 million <0.1% mainly A/HN2, –1% 20,000-00,000 Seasonal flu* Every year <0.0% A/H1N1, and B (0 million - 1 billion) per year * Seasonal flu is not a pandemic, but is listed to compare the several flu strains endemic in humans which produce seasonal flu with the rare new strain that results in a flu pandemic.