April 25, 2009

Mexico Shuts Some Schools Amid Deadly Flu

Outbreak Mexico’s flu season is usually over by now, but health officials have noticed a significant spike in flu cases.

The WHO reported about 800 cases of flu-like symptoms in Mexico in recent weeks, most of most of them among healthy young adultsthem among healthy young adults, with 57

deaths in Mexico City and 3 in central Mexico. That is a worrisome pattern because seasonal flus typically cause most of their deaths among infants and old people, while pandemic flus — like the 1918 Spanish flu, and the 1957 and 1968 pandemics — often strike young, healthy people

the hardest.

• Doctors believe that is because young adults have more vigorous immune systems — which mount an assault on the new virus known as a “cytokine storm” — that may actually overwhelm the victim’s own lungs by causing inflammation and drawing in fluid.

• Like some human strains, it is resistant to two older flu drugs, amantadine and rimantadine. It is not resistant to Tamiflu or Relenza. However, Tamiflu resistance is common in the H1N1 human flu strain circulating this year, so the swine strain could become resistant to Tamiflu if the viruses mixed in humans or, possibly, in pigs.

• In 1976, there was a cluster of swine flu cases among soldiers at Fort Dix, in New Jersey, one of whom died. That led to a rush to make a new vaccine and administer it to 40 million Americans. No epidemic materialized, but thousands of people claimed that the vaccine had given them Guillain-Barré syndrome, which can cause lethargy or paralysis. The episode led to the resignation of the director of the disease control center, and the agency has been wary of causing panic over influenza cases ever since.

April 27, 2009

U.S. Declares Public Health Emergency Over Swine Flu

• American health officials on Sunday declared a public health emergency over increasing cases of swine flu, saying that they had confirmed 20 cases of the disease in the United States and expected to see more as investigators fan out to track down the path of the outbreak.

International Human Cases of Swine Flu InfectionSee: World Health Organization

U.S. Human Cases of Swine Flu Infection(As of April 26, 2009 9:00 AM ET)

State # of laboratory confirmed cases

California 7 cases

Kansas 2 cases

New York City 8 cases

Ohio 1 case

Texas 2 cases

TOTAL COUNT 20 cases

Immune system & Flu

• http://www.metacafe.com/watch/yt-01qwLckBLSM/the_influenza_virus/

Assessing the Danger of New Flu

• The Spanish influenza of 1918 to 1919, had an estimated mortality rate of around 2.5 percent but killed tens of millions of

people because it spread so widely• The new swine flu cases are caused by an influenza strain called H1N1, which appears to be easily passed from person to person. Mexican health authorities have confirmed 149 deaths from that flu and are investigating the illnesses of 1,600 people, and the United States, Canada, Spain and other countries have

confirmed or are investigating cases.• But doctors have little information yet on the mortality rate, as

there is no reliable data on the total number of people infected.

Avian Flu

• In contrast, the lethal avian flu that has kept world health authorities anxious for years is caused by H5N1 influenza virus. It has killed

257 of the 421 people who have contracted it, or 61 percent. But it has shown very little

ability to pass from person to person, mainly infecting poultry, and some experts have

suggested that there may be something about the H5N1 virus that makes it inherently less

transmissible among people.

SARS

• SARS — severe acute respiratory syndrome — is both easily spread and virulent. In the 2003 outbreak in Hong Kong, it killed

299 of the 1,755 people it infected there, or 17 percent.

How does TAMIFLU work?• Neuraminidase is a critical protein on the surface membrane of the

influenza virus38 • Enables the replicated influenza virus to bud from host cell38 • Helps the virus to pass through mucous between cells in the entire

respiratory tract38 • Common to both influenza type A and type B • In in-vitro studies, inhibition of viral neuraminidase is shown to prevent

newly formed influenza virus from escaping infected cells, therefore interrupting the spread of infection between cells38,39

• The relationship between the in vitro antiviral activity in cell culture and the inhibition of influenza virus replication in humans has not been established

• Tamiflu has been studied only in strains of influenza that were circulating at the time.  The magnitude of effect of Tamiflu in treating and preventing novel strains of influenza (such as those that may be involved in a pandemic or associated with avian flu) cannot be predicted.

Tamiflu has not been proven to have a positive impact on the potential consequences (such as hospitalizations, mortality, or economic impact) of seasonal, avian, or pandemic influenza