Global Microbial Threats in the 1990s
II. What actions are taken by the U.S. Government when aninfectious disease outbreak occurs?
For the U.S. Government to help in controlling an incipient - or raging - epidemic in another country, three things must occur. First,reliable information must reach the United States. Second, U.S.scientists and public health officials must evaluate theinformation and decide what measures should be taken. Third, U.S.officials must help the affected country implement thosemeasures. However, U.S. participation in an epidemiologicinvestigation within another nation is dependent upon a formalrequest for assistance from the foreign government. This was thepattern of events during the Ebola virus investigation (see "Lessons Learned From the Ebola Virus Outbreak in Zaire").If no request is received, our Government may still takeaction to minimize the risk of disease importation into theUnited States (see "Plague in India").
The informal global surveillance network
When a cluster of cases of an emerging infectious disease occursin a remote part of Africa, Asia, Eastern Europe, or theAmericas, the international community may or may not learn aboutit. In some cases, an American company or Government agencyoverseas (the Army, Peace Corps, USAID, a U.S. embassy) or an WHOofficial may report an unusual illness to the CDC and seekassistance in testing specimens for diagnosis. Occasionally, acolleague from another industrialized country who is working in adeveloping area will provide the first notification of anemerging disease. Through international conferences andscientific collaborations, U.S. infectious disease experts havemade contacts with colleagues all over the world. As aconsequence, these experts receive informal calls from foreigncolleagues requesting advice and assistance when an unusualoutbreak occurs.
In some cases -- if the notification arrives quickly enough -- thisinformal surveillance system works. When international resourcesare successfully mobilized, assistance in diagnosis, diseasecontrol and prevention can be made available to local healthauthorities. Clinical specimens can be sent to a diagnosticreference laboratory to rule out known disease agents (see "The Informal Global Network"). Epidemiologists can be sentinto the field to investigate the source of the new infection anddetermine how it is transmitted. Public health officials can usethis information to implement appropriate control measures. Oncethe infectious agent has been identified, which is often adifficult task, experimental scientists can start to developdiagnostic tools and treatments if the agent is a newlyrecognized one.
However, a new infectious disease can be easily overlooked,especially when the disease originates in a part of the worldthat lacks effective domestic disease surveillance and moderncommunications. Left unchecked, the disease may spread far andwide before it is recognized and reported.
Evaluation of disease surveillance information
When reports of a potential epidemic and requests for assistancereach the United States, scientists evaluate the information andprovide advice on further investigations, the availability ofdiagnostic tests, and treatment. Within the United States, CDCtakes the lead in evaluating surveillance information. In manyinstances CDC and USAID will offer to send diagnostics, drugs, orvaccines to the affected area.
Response to international disease outbreaks
When the U.S. Government learns of an epidemic in anothercountry, agencies consult with each other on what the UnitedStates response should be. Among the Government agencies withrelevant expertise in this area are CDC, FDA, NIH, DoD, andUSAID.
Lack of an executive function for response to epidemics. The U.S.Government response to international epidemics occurs on an adhoc basis. As described below (and in the inventory thataccompanies this report), many Government agencies anddepartments have resources that can facilitate an effectiveresponse to epidemics of infectious diseases.
The authority of CDC, for instance, does not cover internationaldisease control and prevention, and USAID has limited technicaland financial resources in this area. In practice, individualGovernment workers who become aware of outbreaks do what they canto coordinate agency efforts and provide aid to affectedcountries. But there is no formal structure or designatedresources for this activity.
Resources for emergency responses. At present, the U.S. Government has no funds set aside for responses to internationaldisease outbreaks. Government disaster assistance groups such asthe Federal Emergency Management Administration and USAID'sOffice of Foreign Disaster Assistance (OFDA) do not takeresponsibility for infectious disease emergencies. At CDCalthough approximately65% of the budget is dedicated to the prevention andcontrol of infectious diseases, about 95% of these funds areearmarkedfor AIDS, TB, and sexually transmitteddiseases and vaccine preventable diseases. Moreover, USAIDhas limited resources available for international outbreakinvestigations. Thus, when a new or re-emerging disease issuspected in another country, there is very little flexibility inany U.S. Government agency's budget to provide for aninvestigation.
Importation of infectious diseases into the United States. Eachtime an infected person (or a contaminated food or sick animal)enters the United States, an opportunity arises for a contagiousmicrobe to spread to the American people. CDC strives to preventthis in two ways. One protective measure is to issue advisoriesthat caution against travel to or from the site of an epidemic.CDC also provides information on travelers' health, includinginformation on recommended vaccinations and on regimens for drugprophylaxis. A more comprehensive line of defense relies on localsurveillance systems, at the state, county, and city levels.Unfortunately, our local public health surveillance systems areno longer adequate because of our past complacency aboutinfectious diseases, poor planning, and lack of resources.
Screening of travelers at U.S. ports of entry. Under the PublicHealth Service Act and the Foreign Quarantine Regulations, allaircraft and ships captains are required to radio the nearest CDCquarantine station at their port of arrival when they have an illperson or when a passenger has died. CDC has the authority todetain, isolate, or conditionally release any person believed tobe infected or exposed to a communicable disease. CDC staffsquarantine stations at seven ports of entry at major airports inNew York, Miami, Chicago, Seattle, San Francisco, Los Angeles,and Honolulu. Each station provides backup for other ports intheir geographic area of responsibility. At ports of entry whereCDC does not have staff, the gap is filled by airline workers, byphysicians on contract with CDC, and by officials of theImmigration and Naturalization Service (INS). U.S. civilians,foreign nationals (including tourists, business travelers,long-term visitors), and immigrants can enter at any of theseairports, as well as seaports and land border areas. There areapproximately 50 international airports in the United States andmore than 150 other legal entry points.
The identification of persons carrying pathogens capable ofcausing serious disease outbreaks is made difficult by the verylarge number of people entering the United States fromincreasingly remote locations. Most American cities can bereached within 36 hours from anywhere in the world, either bydirect or by connecting flights. The incubation periods of mostinfectious diseases (the time between infection and theappearance of symptoms) is considerably longer than 36 hours.Because only obviously ill patients are identified by screeningat ports of entry, routine state and local surveillance effortsare relied on to identify infected travelers who become ill sometime after entry into the United States.
Screening of soldiers. Military personnel who return to theUnited States are not routinely quarantined. Military personnelwho become ill overseas are evacuated to DoD medical facilitiesin the United States. Military personnel who are not sick returnto their unit bases. Deployed reservists are more apt to re-entercivilian health-care channels than active duty personnel. Themedical tracking of all deployed military personnel after theyreturn home is being improved by DoD to facilitate therecognition and diagnosis of latent infections.
Food-borne and animal-borne diseases. CDC's quarantine programalso coordinates with the U.S. Department of Agriculture (USDA),U.S. Fish and Wildlife Services, Department of Interior, and FDAto ensure that other possible carriers of human disease (food andanimals) are managed appropriately.
USDA's Food Safety and Inspection Service (FSIS) plays animportant role in disease control and eradication. FSIS samplesfood products for a number of pathogens and protects the foodsupply by retaining or recalling products. FSIS inspects forconditions and collects samples to test for many diseases such asrabies, tuberculosis, brucellosis, and pseudorabies which can betransmitted to humans. This inspection is crucial for thesurveillance and monitoring system of the USDA-APHIS.
The Animal and Plant Health Inspection Service (APHIS) of theUSDA is
responsible for protecting American livestock and poultryfrom foreign and
domestic diseases. Many diseases of humans arecarried by and transmitted from
animals or animal products(Ebola, anthrax, cryptosporidium, hantavirus, Rift
Valley fever, Lyme disease, E. coli, tuberculosis, brucellosis,
rabies,pseudorabies, to name to few). APHIS carries out thisresponsibility
through several activities:
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