MANILA, 15 May 2009, 1600 hrs—New Zealand reported two new laboratory confirmed cases of influenza A (H1N1), bringing the total confirmed case count in that country to nine. No deaths from influenza A(H1N1) have been reported in the Western Pacific Region.
New Zealand's two new cases comprise a member of the original student group from Auckland's Rangitoto College which returned to New Zealand on 25 April from a trip to Mexico, and another passenger on the same flight. Both cases have been treated and have fully recovered.
There are now 21 confirmed cases of influenza A(H1N1) in the Western Pacific Region:
- 1 in Australia, reported 9 May
- 2 in China, reported 11 May, 13 May
- 2 in Hong Kong (China), reported 1 May, 13 May
- 4 in Japan, 3 reported 9 May, 1 reported 10 May
- 9 in New Zealand, 3 reported 28 April, 1 reported 1 May, 1 reported 4 May, 2 reported 9 May, and 2 reported 15 May.
- 3 in the Republic of Korea, reported 2 May, 5 May and 7 May
Why influenza A(H1N1) isn't seasonal influenza
Though much is unknown about influenza A(H1N1) and it is still early in the outbreak, information collected so far appears to indicate that influenza A(H1N1) is somewhat different from seasonal influenza. This is not surprising as it is a newly identified virus to which populations are likely to have little or no immunity. It is therefore important that governments continue to prepare for pandemic and do not assume that outbreaks of influenza A(H1N1) will now, or in the future, be just like seasonal influenza.
An analysis of early data from Mexico published on 12 May in the journal Science and facilitated by the WHO Rapid Pandemic Assessment Collaboration points out that early fatality rates from influenza A(H1N1) in Mexico were similar to those seen during the 1957 influenza pandemic – higher than seasonal influenza but nowhere near as high as those seen during the 1918 pandemic.
Influenza A(H1N1) also appears to be more transmissible than seasonal influenza. Computer modeling based on the early data from Mexico estimates that up to three times as many people may have been infected with influenza A(H1N1) than would have been expected if the outbreak had been caused by seasonal influenza. It should be noted however that though influenza A(H1N1) transmission rates are higher than for seasonal influenza they are nowhere near as high as seen during the 1918 pandemic.
Another departure from typical patterns of seasonal flu outbreak is that younger people appear to be more likely to become infected than older people. Half of all serious cases to date have been young and otherwise healthy people between the ages of 25 and 44. Only 5% of all reported cases have occurred in people over 50 years of age – a stark contrast to seasonal influenza which often disproportionately affects the elderly.
And finally around one third of people with influenza A(H1N1) have suffered from diarrhea – a much high frequency than is usually seen with seasonal influenza.
Influenza A(H1N1) has killed 65 people globally and around 10% of all reported cases have needed hospitalization. Accordingly, WHO strongly discourages so-called "flu parties" held in the belief that catching influenza A(H1N1) before it mutates will provide immunity to any future strains. Although the majority of people with influenza A(H1N1) appear to have a self limiting illness, infection with this virus has caused serious illness in some people and it is not known whether infection now would offers any protection against future strains of the virus.
Global case count
As of 06:00 GMT, 15 May 2009, 34 countries have officially reported 7457 cases of influenza A(H1N1) infection, with 65 deaths. Mexico has reported 2446 laboratory-confirmed human cases of infection, including 60 deaths. The United States of America has reported 4298 laboratory-confirmed human cases, including three deaths. Canada has reported 389 laboratory confirmed human cases, including one death. Costa Rica has reported eight laboratory-confirmed human cases, including one death.
The following countries have reported laboratory confirmed cases with no deaths: Argentina (1), Australia (1), Austria (1), Brazil (8), China (2), Hong Kong (China) (2), Colombia (10), Cuba (1), Denmark (1), El Salvador (4), France (14), Germany (12), Guatemala (3), Ireland (1), Israel (7), Italy (9), Japan (4), Netherlands (3), New Zealand (9), Norway (2), Panama (39), Poland (1), Portugal (1), Republic of Korea (3), Spain (100), Sweden (2), Switzerland (1), Thailand (2) and the United Kingdom (71).
WHO is not recommending travel restrictions related to the outbreak of the influenza A(H1N1) virus. Individuals who are ill should delay travel plans and returning travellers who fall ill should seek appropriate medical care. These recommendations are prudent measures which can limit the spread of many communicable diseases, including influenza.
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