Swine flu–The Real Thing?

  • Current Status of the epidemic:

Mexico: almost 2000 suspected infections, 152 suspected deaths from swine flu – 20 confirmed deaths,

US: 50 confirmed cases (Ohio 1 case, Kansas 2 cases, Texas 2 cases, New York 28 cases and California 7 cases)

Canada: 6 confirmed cases

New Zealand – 3 confirmed cases

UK – 2 confirmed cases

Spain- 2 confirmed cases

Israel – 1 confirmed case

Countries with suspected cases: Brazil, Guatemala, Peru, Australia, and South Korea, and seven EU states

This outbreak, more here and here, has potential for a pandemic, an event anticipated and feared by infectious disease epidemiologists for the last 80 years. A H1N1 virus (similar to the causative agent of the1918 epidemic) has jumped from swine to man and has shown the ability to pass through several generations of infected individuals.

WHO deputy chief Keiji Fukuda said this was a “significant step towards pandemic influenza” but a pandemic should not be considered inevitable.

“Hugh Pennington, a leading bacteriologist in the UK, said on Tuesday that it was difficult to make any predictions about the outbreak because of its nature. It’s a new virus – we’ve never before seen this combination of swine virus and human virus genes,”

What can be presumed at present:

1. If the disease spreads worldwide, there will be excess mortality. As bad as the 1918 episode, not so far. We don’t have enough information to estimate mortality rates. Of interest was the severity of the disease in 1918 among younger groups. That implied residual immunity from earlier viral disease exposure that protected the elderly. It’s too early to tell whether there will be a similar pattern with the current problem.

Watch out for the disease in overpopulated areas. In 1918 the world’s population was 1.8 billion and the virus killed over 50 million people. Our population now is approaching 7 billion.

2. The severity of the disease is unclear. In Mexico mortality appears significantly higher than elsewhere, so far. This may be deceptive if the cases we know of represent a small part of those infected–the rest with minor upper respiratory disease. (as implied in this Guardian article) Alternatively, the Mexican experience may represent a virus with more severe ramifications that altered pathogenicity with passage through succeeding generations of infected people. A question of great concern is whether a more pathogenic strain will emerge. In 1918, there were periods when the virus appeared to be less severe and then abruptly changed. We’re still not sure what happened then but it’s possible, perhaps likely, that a similar course can occur now.

3. Those with impaired immune systems will be particularly vulnerable.

5. The CDC notes regarding antiviral drugs: ”

“There are four influenza antiviral drugs approved for use in the United States (oseltamivir, zanamivir, amantadine and rimantadine). The swine influenza A (H1N1) viruses that have been detected in humans in the United States and Mexico are resistant to amantadine and rimantadine so these drugs will not work against these swine influenza viruses. Laboratory testing on these swine influenza A (H1N1) viruses so far indicate that they are susceptible (sensitive) to oseltamivir and zanamivir.”

While oseltamivir (Tamiflu) and zanamivir (Relenza) may have activity in lab settings, there is no information yet whether they will prevent complications or mortality in actual patients.

CDC does recommend:

Treatment: If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious influenza complications. For treatment, antiviral drugs work best if started as soon after getting sick as possible, and might not work if started more than 48 hours after illness starts.”

Prevention: Influenza antiviral drugs also can be used to prevent influenza when they are given to a person who is not ill, but who has been or may be near a person with swine influenza. When used to prevent the flu, antiviral drugs are about 70% to 90% effective. When used for prevention, the number of days that they should be used will vary depending on a person’s particular situation.”

6. Vaccine development and testing will take some time, at least 4 months, probably more.

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