Update: Swine Flu Situation in US and Mexico

Over the past week, there have been confirmed human cases of a new influenza virus - swine influenza (H1N1) - in the Southwest United States (8 confirmed cases) and Mexico (19 confirmed cases). The CDC and WHO have stated that the strains circulating in the US and Mexico are identical H1N1 strains.

The H1N1 strain is NOT related to H5N1 avian influenza. H5N1 avian influenza is circulating primarily in Southeast Asia and has caused concern over its potential to cause a pandemic. This unusual strain of H1N1 virus is primarily a swine influenza, including genes from North American swine and avian influenza, human flu, and a European/Asian strain of swine flu.

WHO, PAHO, CDC, and Mexican and Canadian health authorities are collaborating in the ongoing investigation to determine the extent of the virus' spread, transmissibility, and severity. Thus far there is evidence of human-to-human transmission of the virus.

While the situation is concerning and world health agencies continue to monitor the situation carefully, there is no reason to believe this is the start of a pandemic. In fact, there are currently no travel restrictions to the Southwest US (California and Texas) or Mexico at this time. WHO has not raised the pandemic threat level. However, CDC and WHO are encouraging all nations to consult their pandemic preparedness plans and remain alert. CDC will be holding daily briefings on the situation over the next few days.

Below is some more detailed information concerning the outbreaks and the public health response to the situation.

UNITED STATES:

US CASES: 8 non-fatal cases of H1N1 have been confirmed by the CDC in California and Texas. At least one of these cases, a young boy from California, had traveled to Mexico recently.

CLINICAL TREATMENT GUIDELINES: Thus far, CDC clinical guidelines suggest treating the illness with oseltamivir (Tamiflu) and zanamavir (Relenza). All US cases have been successfully treated using this course. Thus far all cases have been resistant to adamantanes.

MEXICO:

LAB-CONFIRMED CASES: Mexican health officials sent 32 samples to the Canadian Public Health Agency and CDC; together they have confirmed the same strain of H1N1 circulating in the US in 19 of the 32 samples. All agencies continue to gather samples and test for H1N1 to get a better understanding of the severity, transmissibility, and spread of the virus.

PANDEMIC THREAT LEVEL:
· The world is currently at level 3 of the WHO's six-rung pandemic alert ladder.
o Phase 3 means there are occasional human cases with a novel flu virus.
· WHO plans to convene a panel to determine whether to raise the pandemic threat level. WHO would need the advice of an expert panel to move to Phase 4 or beyond.
· Phase 6 is a pandemic.

FOR MORE INFORMATION:
From WHO:
http://www.who.int/csr/don/2009_04_24/en/index.html
From CDC:
http://www.cdc.gov/flu/swine/http://www.cdc.gov/flu/swine/investigation.htm

From open source media (further information about the situation in Mexico):
http://www.theglobeandmail.com/servlet/story/RTGAM.20090424.wflumain0424/BNStory/International/home
http://www.cbc.ca/health/story/2009/04/24/health-flu-mexico090424.html?ref=rss
http://www.alertnet.org/thenews/newsdesk/LO332728.htm
http://www.bloomberg.com/apps/news?pid=20601124&sid=azAqR4.k2qEY&refer=home
http://online.wsj.com/article/SB124058255179552887.html