Confirmed Cases of Swine Influenza Jumps to 40 in US; Additional Cases Confirmed Internationally

Reported April 27, 2009, WASHINGTON, DC.

Today the Centers for Disease Control and Prevention (CDC) reported that the known number of laboratory-confirmed human cases of swine influenza A/H1N1 has doubled in the United States; the total is now 40. The 20 new cases were confirmed in New York. No new cases have been reported in any other US states, and no deaths have been reported.

Human cases of swine influenza A/H1N1 virus infection also have been confirmed internationally: Canada has reported 6 confirmed human cases of infection; Spain has reported 1 case; Scotland has reported 2 cases. Mexico has reported 26 cases of infection, including 7 deaths.

On the advice of the Emergency Committee of the World Health Organization, the Director-General has raised the level of influenza pandemic alert from the current phase 3 to phase 4. The change to a higher phase of pandemic alert indicates that the likelihood of a pandemic has increased, but not that a pandemic is inevitable.

The Emergency Committee's recommendation is based on the available data on confirmed outbreaks of A/H1N1 swine influenza in the United States, Mexico, and Canada. The Committee also considered reports of possible spread to additional countries.

As further information becomes available, WHO may decide to either revert to phase 3 or raise the level of alert to another phase. This decision was based primarily on epidemiological data demonstrating human-to-human transmission and the ability of the virus to cause community-level outbreaks.

Given the widespread presence of the virus, the Director-General considered that containment of the outbreak is not feasible. The current focus should be on mitigation measures.

WHO has not issued any travel restrictions or border closures; however, the agency recommends people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention. In addition, the CDC recommends forgoing any nonessential travel to Mexico.

The WHO Director-General considered that production of seasonal influenza vaccine should continue at this time, subject to re-evaluation as the situation evolves. WHO will facilitate the process needed to develop a vaccine effective against A/H1N1 virus.

In the United States, the median age of the confirmed cases is 16 (range, 7-54 years). All but 1 of the 40 US cases (California, 7; Kansas, 2; New York, 28; Ohio, 1; and Texas, 2) have recovered or are recovering without hospitalisation.

In Mexico, the suspected number of cases is reportedly as high as 1,600, and the suspected number of deaths in Mexico is up to 80. Potential new cases also have been reported in France, Hong Kong, and New Zealand. These numbers and reports are not yet confirmed.

The CDC confirmed that the US cases have been more benign than those reported in Mexico; however, more cases are expected to be identified in the United States.

Laboratory testing has found the swine influenza A/H1N1 virus is susceptible to the prescription antiviral drugs oseltamivir and zanamivir. According to Anne Schuchat, MD, the CDC's Interim Deputy Director for Science and Public Health Program, treatment should begin within 48 hours of onset. However, she stressed that many of the US cases recovered without treatment. Vaccine development is in process, but it will take several months to prepare a vaccine.

The US Department of Homeland Security has confirmed the release of approximately 11 million treatment courses of the antiviral drugs oseltamivir and zanamivir from the Strategic National Stockpile, making them available to all states but prioritising the affected states. This represents approximately 25% of the 50 million treatment courses currently in the US national stockpile.

CDC has issued interim recommendations for diagnostic testing and antiviral use to US hospitals and emergency rooms, but local and state circumstances may vary and individual protocols may be put in place.

The CDC also has prepared interim guidance on how to care for people who are sick and interim guidance on the use of face masks in a community setting where spread of this swine flu virus has been detected. This is a rapidly evolving situation; CDC and WHO will provide new information as it becomes available.

SOURCE: World Health Organization, Center for Disease Control and Prevention, US Department of Homeland Security