1. What is H1N1?

The influenza virus is divided into three types-A, B and C-with the influenza A virus affecting mammals and birds, influenza B virus infecting only humans and seals, and influenza C virus causing very mild symptoms. H1N1 is a subtype of the influenza A virus. The H and N refer to two glycoproteins that coat the surface of the virus: H stands for hemagglutinin, which allows the virus to invade human cells, while N (neuraminidase) is a special protein that stops adsorption after the virus replicates, facilitating the spread of the virus and allowing it to infect more cells.

The subtypes of hemagglutinin range from 1 to 16, while the neuraminidase subtypes are numbered 1 through 9. The reassortment of hemagglutinin and neuraminidase results in viruses with different degrees of virulence causing different symptoms, and the host organisms they infect also differ. A most arduous task for virologists is the annual "guessing game" of predicting what form the next wave of flu will manifest, so that enough preventive vaccines for the forecasted virus can be made available in a timely fashion to the elderly and vulnerable.

The viruses mutate yearly, but perhaps every 10 to 30 years there is a major mutation. The novel flu virus appears to be a mutation of the Spanish Flu virus of 1918, which was H1N1. But it's different from the "swine flu" of that year: this new virus is a reassortment of genes from people, pigs and poultry.

The true face of H1N1 swine flu.

2. How virulent is H1N1?

"Novel H1N1 is not SARS!" emphasizes Dr. Lee Ping-ing, spokesman of the Infectious Diseases Society of Taiwan and an associate professor in pediatric diseases at National Taiwan University.

Though the symptoms of fever, coughing and shortness of breath are comparable, it differs from the SARS (Severe Acute Respiratory Syndrome) virus that emerged in the spring of 2003 in that SARS was caused by a never-before-seen coronavirus which had no relation to the flu virus. When medical researchers saw the disease for the first time, they were unable to identify it, and had no way of preventing or treating it. The first person to isolate the SARS virus, Italian virologist Dr. Carlo Urbani, died in the line of duty because of this. SARS spread to 22 countries, and though not many people were infected, it was troublesome to handle since it caused pulmonary fibrosis, leading to 229 deaths worldwide, a mortality rate of 7-15%.

On the other hand, although this new strain of H1N1, due to its greater virulence, showed a slightly elevated initial mortality rate (2%) as compared to the ordinary seasonal flu (0.1%), it is still a typical form of influenza, with symptoms such as fever, fatigue, muscle aches, sore throat, cough, headache and diarrhea, making it familiar to most physicians. Sufferers usually recover fully within a week, and 30% of those infected display no symptoms at all and recover naturally.

And there are treatments for novel H1N1, which is its biggest difference from SARS. The antiviral drug Tamiflu, used for ordinary seasonal influenza, reacts very effectively against H1N1. That is to say, medical circles already have a precise grasp on the structure of the new virus, and also have proven mass-produced drugs at hand. Once the vaccine for this virus becomes available (locally produced vaccines are currently undergoing human trials), it will not be difficult to control it.

3. Screen, take your meds

In contrast to SARS, which is contagious only once fever breaks out, novel H1N1 is contagious from the day before symptoms strike until around seven days after. Indeed some 30% of those who contract the illness experience no fever at all. Thus screening cannot be achieved just by use of ultraviolet sensors, and H1N1 prevention efforts have quickly moved from airports and borders into communities.

Clinics are now using rapid screening, which provides results within the hour. Samples are collected from throat and nasal cavity swabs, which are tested for influenza A virus antigens. With a sensitivity of only 60-70%, a negative screening result (about half of those tested) does not eliminate the possibility of infection. But if the results are positive, it's not clear without further tests whether the virus is novel H1N1 flu, or this year's seasonal H3N2 flu, or even avian flu (H5N1). Dr. Lee Ping-ing says that according to community monitoring by Taiwan's Centers for Disease Control (CDC), 87% of the current wave of influenza A virus is H1N1.

People become jittery when a new virus emerges, so doctors are instructed to prescribe the antiviral drug Tamiflu immediately upon positive screening results. Once full-blown symptoms develop, it's too late to administer this drug.

Tamiflu inhibits neuraminidase, keeping the flu virus from replicating and spreading to other cells in the body; therefore it's effective at reducing the gravity of infection and shortening the course of disease. Lee says that with sufficient inventory (currently enough for 18% of Taiwan's population, with plans to increase to 30%), early administration of the drug may be safer, but if the drug is in short supply or there are concerns of drug resistance (due to those who don't complete the five-day course of the drug), then other measures need to be considered.

Clinically, medical professionals have yet to determine whether the 48-hour "golden window" for administering Tamiflu applies to this virus, and even whether it's necessary to prescribe Tamiflu in the first place. Taiwan Medical Association president Lee Ming-been believes that not everyone who has contracted novel H1N1 flu needs to take medication. Quite apart from the 30% or so of sufferers who have no symptoms at all, even those who experience coughing and fever do not urgently need treatment. Even when fall and winter seasonal flu prevailed in the past, Taiwan's general practitioners rarely gave Tamiflu to mild sufferers.

Given that the vast majority of sufferers only experience mild illness, there is the risk of Tamiflu misuse. When the patient feels better, he may take it upon himself to stop taking the medicine, and any remaining viruses may become resistant and can infect other people. This is the greatest nightmare of the medical community. As Wang Jen-hsien, head of the CDC's Central Epidemics Command Center, says, in such a case, "Even activating the National Security Mechanism wouldn't be enough!"

Lee basically favors the use of Tamiflu, but he reminds us that the seasonal flu usually passes after a day or two; hence the "golden window" of 48 hours within which to take the medicine. But with this new flu strain, some patients remain feverish for a week or two, so the situation is not necessarily equivalent. So if the patient's condition keeps worsening, Tamiflu should be administered no matter how many days it has been since the onset of the flu.

4. Why young adults?

Most people hospitalized for ordinary seasonal flu are over 65 with weakened immune systems (44%). But this time around, the lion's share of those hospitalized for severe symptoms such as encephalitis, pneumonia and myocarditis have been children and young adults. This is reminiscent of the SARS epidemic (the immune system triggers a storm of cytokines to fend off invaders, like a scorched earth battle, and this is more likely to occur in those with better disease resistance), making it cause for particular concern.

Lee says that one possible explanation is that the Spanish Flu virus, H1N1, has lain low since its last appearance in 1957, so about a third of those born before 1957 have been infected by H1N1. Thus their immune systems still have some capacity to identify this virus. In contrast, those under 50, who lack the antibody, are at elevated risk.

Mexican figures on the novel H1N1 flu reveal that the deaths all occurred among people between ages 25 and 45, and among cases in Taiwan where people have been hospitalized, the 25-49 age group has the highest representation (at 26%). Lee believes that schoolchildren were safe because they remained at home over the summer, while young adults, at their peak of activity, were at highest risk of infection.

Infection rates jumped among students after the start of school in September. The DOH's current "325" rule (a three-day period with two infections in a class means five days of cancelled class) seeks to balance prevention with students' education rights. "This is the strictest standard in the world for prevention of this disease," notes DOH minister Yang Chih-Liang: as long as all schools abide by this rule, parents can feel at ease.

5. When will it peak?

Those familiar with the Spanish flu of 1918 are aware that H1N1 did not draw much notice when it first appeared in the summer of 1917. Nobody thought that six months later it would bounce back and grow into a worldwide calamity. Now, people are asking questions about the flu of 2009, which was also rare in the summer before its reemergence: "When will it reach its peak?" "Will there be another, more virulent wave?"

For this reason, some people believe that as long as medical resources are sufficient, being infected early and developing antibodies is not a bad thing. Lee believes that as pediatric outpatient services are being overwhelmed, "The current novel H1N1 flu pandemic has reached a substantial scale," but once vaccines start to be administered, the situation will be easier to control.

Taiwan, are you ready?

Unease and fear have spread along with the H1N1 virus, with healthy people fearing infection and the infected concerned that it may become life threatening. Some worry about shortages of facemasks or Tamiflu, and secretly hoard them, while others worry that there aren't enough hospital beds. Some, fearing hospital infections, are enduring other illnesses to avoid seeking treatment. The panic erupting in the late summer may be worse than the disease: some people are succumbing to panic disorder while never having to actually struggle with H1N1.

The sense of panic among the people of Taiwan comes mainly from their experience with SARS. However, most are unaware that even in a "normal" year, over 4,000 die in Taiwan from seasonal flu, and even in the US, with its advanced medical know-how, some 30,000 people die of the flu. And with countries around the world on full alert against the novel H1N1 flu, there is little difference in mortality rate when compared to ordinary flu. It is expected that as vaccines become available worldwide, the mortality rate will continue to drop.

Says Lee Ping-ing, H1N1 differs from peculiar, furtive SARS in that it will eventually become the kind of seasonal flu that regularly breaks out. The only thing we can do is to find the least harmful means of coexisting with it. Besides health education, "The most direct tactic is vaccination," says Lee, anticipating the mid-November release of the vaccine by Adimmune Corp., which could greatly reduce morbidity and mortality figures.

Summing up this flu wave, "This 'mild' pandemic is unstoppable," says DOH minister Yang Chih-liang. CEOs, white-collar workers, blue-collar workers and students alike are susceptible. It's important that clinical observations thus far show us it's not as dire as had been predicted. Though the public should be wary, there's no need to be too worried. Keeping physically and mentally fit is the best way to fight the virus naturally!