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In 2005, the World Health Assembly adopted a revision of the International Health Regulations (IHR), giving a new mandate to WHO and member states to increase their respective roles and responsibilities for the protection of international public health. The IHR(2005) require signatory nations (which include the United States) to notify WHO of all events that may constitute a “Public Health Emergency of International Concern,” and to provide information regarding such events. The IHR(2005) also include provisions regarding designated national points of contact, definitions of core public health capacities, disease control measures such as quarantine and border controls, and others. The IHR(2005) require WHO to recommend, and signatories to use, control measures that are no more restrictive than necessary to achieve the desired level of health protection.

On April 25, 2009, upon the advice of the Emergency Committee called under the rules of the IHR(2005), the WHO Director-General declared the global threat of H1N1 flu a Public Health Emergency of International Concern. This designation calls upon signatories to provide timely and transparent notification of events to WHO, to collaborate with other countries in disease reporting and control, and to adopt effective risk communication strategies to reduce the potential for international disease spread and the likelihood of unilateral imposition of trade or travel restrictions by other countries.

Travel Guidance

A number of governments have instituted enhanced passenger screening practices at their borders, and policymakers have debated more extensive prohibitions against the entry of travelers from countries or areas affected by the outbreak. The WHO has consistently advised against movement restrictions as a means to control influenza, citing a lack of evidence of their effectiveness, coupled with their potentially harmful effects on public confidence, local economies, and trade.

Food Safety Guidance

WHO has published a joint statement with Food and Agriculture Organization of the United Nations (FAO), the World Organization for Animal Health (known by its French acronym, OIE), and the World Trade Organization (WTO), saying:

In light of the spread of influenza A(H1N1), and the rising concerns about the possibility of this virus being found in pigs and the safety of pork and pork products, we stress that pork and pork products, handled in accordance with good hygienic practices recommended by the WHO, FAO, Codex Alimentarius Commission and the OIE, will not be a source of infection.

To date there is no evidence that the virus is transmitted by food. There is currently therefore no justification in the OIE Terrestrial Animal Health Standards Code for the imposition of trade measures on the importation of pigs or their products.


Key U.S. Government Actions

Department of Homeland Security (DHS)

Leadership Designation


On April 27, Janet Napolitano, Secretary of the Department of Homeland Security (DHS), stated in a press briefing that she was serving as the coordinator of the federal response to the flu outbreak, having assumed the role of Principal Federal Official (PFO).12 According to the National Response Framework (NRF), which guides a coordinated federal response to disasters and emergencies in general, the Secretary of Homeland Security leads federal incident response.

Customs and Border Protection (CBP) Activities

Customs and Border Protection (CBP), in DHS, is reportedly monitoring incoming travelers at ports of entry (typically a visual inspection for possible symptoms), providing information about disease control measures, and referring symptomatic persons to a CDC quarantine station or a local public health official for evaluation. According to CBP, “at this time all U.S. ports of entry are open and operating as normal with officers using risk based border screening.

Administration officials resisted calls to implement more aggressive measures such as closing the U.S.-Mexico border. They commented that such a measure could be highly disruptive and not necessarily effective at controlling the spread of disease, and argued instead that the new flu strain is already in the United States, and that the focus of mitigation strategies is on where U.S. illnesses are being reported, and on patients’ families and their surrounding communities. WHO and CDC officials have commented that scientific evidence does not support closure of a border to travelers as an effective means of controlling the spread of influenza.

Department of Health and Human Services (HHS)

Determination of a Public Health Emergency

On April 26, Charles E. Johnson, then the Acting HHS Secretary, who is responsible for coordinating the public health and medical response to the flu outbreak, declared a public health emergency pursuant to Section 319 of the Public Health Service Act. Among other things, this authority enables FDA to implement an authority in the Federal Food, Drug, and Cosmetic Act— the so-called Emergency Use Authorization (discussed below)—allowing for the use of unapproved medical treatments and tests, under specified conditions, if needed during an incident.

FDA: Emergency Use Authorizations

If an emerging public health threat is identified for which no licensed or approved product exists, the Federal Food, Drug and Cosmetic Act authorizes the FDA Commissioner to issue an Emergency Use Authorization (EUA) so that unapproved but potentially helpful countermeasures can be used to protect the public health. On April 27, pursuant to authority provided by the prior public health emergency determination, FDA issued EUAs to allow emergency use of (1) oseltamivir (Tamiflu) and zanamivir (Relenza) for the treatment and prophylaxis of influenza; (2) disposable respirators for use by the general public; and (3) an unapproved diagnostic test for the new flu strain.

CDC: Travel Notices

On April 27, CDC issued a Travel Health Warning, its highest advisory level, recommending that U.S. travelers avoid all nonessential travel to Mexico. (The agency had issued a Travel Health Precaution, the next lower advisory level, on April 25.) On April 28, the Department of State issued a travel alert to U.S. citizens of the health risks of travel to Mexico due to the flu outbreak, noting the CDC’s Travel Health Warning of the previous day. On May 15, CDC downgraded the Travel Health Warning for Mexico, returning to the precaution level, and the Department of State lifted its travel alert. Travelers to Mexico are advised to be alert regarding local conditions, practice good hygiene, and consult with their physicians regarding any health conditions that could put them at higher risk of illness. Each of these advisories regarding travelers leaving the United States is voluntary.

CDC: Disease Surveillance

Because illnesses with the novel H1N1 flu have generally been mild, health officials acknowledge that the disease may be substantially underreported. It is likely that for every infection that results in a health care encounter and a confirmed laboratory test, there are many mild infections for which victims don’t seek care, and silent infections in which individuals may be infectious to others in the absence of symptoms. Health officials in many U.S. states and cities have stopped running confirmatory tests on every suspected case of H1N1 influenza, feeling that better use of epidemiology and laboratory resources can be made by monitoring disease spread to new areas, rather than repeatedly confirming its presence in an affected area.

To get a clearer picture of the magnitude and spread of disease in the United States, CDC has begun tracking the H1N1 outbreak using its multi-layered surveillance system for seasonal flu. The system showed that during the week ending May 30, 2009, there were higher levels of flulike illness than is normal for this time of year, that flu activity had decreased in comparison to the previous few weeks, and that approximately 82% of all flu viruses reported to CDC that week were the new H1N1 strain.

To track seasonal flu, CDC collects, compiles, and analyzes information from various sources year round, and publishes a weekly report from October through mid-May. The surveillance system is a collaboration between CDC and state and local health departments, public health and private clinical laboratories, vital statistics offices, health care providers, clinics, and emergency departments. Information is collected from several different data sources, as follows:

• Viral Surveillance: About 80 U.S. WHO Collaborating Laboratories and 70 National Respiratory and Enteric Virus Surveillance System (NREVSS) laboratories across the country report the number of respiratory specimens tested and the number positive for flu virus. All state public health laboratories participate as WHO collaborating laboratories, along with some county public health laboratories and some large medical centers. Most NREVSS participants are hospital laboratories.

• Outpatient Illness Surveillance: Information on patient visits to health care providers for influenza-like illness (ILI) is collected through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet).

• Mortality Surveillance: Rapid tracking of influenza-associated deaths is done through two systems:
(1) The 122 Cities Mortality Reporting System. Each week, the vital statistics offices of 122 cities report the total number of death certificates received and the number of those for which pneumonia or influenza was listed as the underlying or contributing cause of death;
(2) Surveillance for Influenza-associated Pediatric Mortality. Influenza-associated deaths in children is a nationally notifiable condition. Laboratory-confirmed influenza-associated deaths in children are reported through the National Notifiable Disease Surveillance System.

• Hospitalization Surveillance: Two systems monitor hospitalizations with laboratory confirmed flu infections:
(1) The Emerging Infections Program (EIP) Influenza Project conducts surveillance for laboratory-confirmed influenza-related hospitalizations in children and adults in 60 counties covering 12 metropolitan areas of 10 states.
(2) The New Vaccine Surveillance Network (NVSN) provides estimates of laboratory-confirmed flu hospitalization rates for young children in three counties: Hamilton County, OH; Davidson County, TN; and Monroe County, NY.

• Summary of the Geographic Spread of Influenza: State health departments report the estimated level of spread of flu activity in their states each week through the state and territorial epidemiologists’ reports.



Source :
The 2009 Influenza Pandemic: An Overview
Sarah A. Lister Specialist in Public Health and Epidemiology
C. Stephen Redhead Specialist in Health Policy
June 12, 2009

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