SARS-CoV-2 Cases Reported on International Arriving and Domestic Flights: United States, January 2020-December 2021.

Objectives. To describe trends in the number of air travelers categorized as infectious with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2; the virus that causes COVID-19) in the context of total US COVID-19 vaccinations administered, and overall case counts of SARS-CoV-2 in the United States. Methods. We searched the Quarantine Activity Reporting System (QARS) database for travelers with inbound international or domestic air travel, a positive SARS-CoV-2 lab result, and a surveillance categorization of SARS-CoV-2 infection reported during January 2020 to December 2021. Travelers were categorized as infectious during travel if they had arrival dates from 2 days before to 10 days after symptom onset or a positive viral test. Results. We identified 80 715 persons meeting our inclusion criteria; 67 445 persons (83.6%) had at least 1 symptom reported. Of 67 445 symptomatic passengers, 43 884 (65.1%) reported an initial symptom onset date after their flight arrival date. The number of infectious travelers mirrored the overall number of US SARS-CoV-2 cases. Conclusions. Most travelers in the study were asymptomatic during travel, and therefore unknowingly traveled while infectious. During periods of high community transmission, it is important for travelers to stay up to date with COVID-19 vaccinations and consider wearing a high-quality mask to decrease the risk of transmission. (Am J Public Health. 2023;113(8):904-908. https://doi.org/10.2105/AJPH.2023.307325).

Monkeypox Outbreak - Nine States, May 2022.

On May 17, 2022, the Massachusetts Department of Public Health (MDPH) Laboratory Response Network (LRN) laboratory confirmed the presence of orthopoxvirus DNA via real-time polymerase chain reaction (PCR) from lesion swabs obtained from a Massachusetts resident. Orthopoxviruses include Monkeypox virus, the causative agent of monkeypox. Subsequent real-time PCR testing at CDC on May 18 confirmed that the patient was infected with the West African clade of Monkeypox virus. Since then, confirmed cases* have been reported by nine states. In addition, 28 countries and territories,† none of which has endemic monkeypox, have reported laboratory-confirmed cases. On May 17, CDC, in coordination with state and local jurisdictions, initiated an emergency response to identify, monitor, and investigate additional monkeypox cases in the United States. This response has included releasing a Health Alert Network (HAN) Health Advisory, developing interim public health and clinical recommendations, releasing guidance for LRN testing, hosting clinician and public health partner outreach calls, disseminating health communication messages to the public, developing protocols for use and release of medical countermeasures, and facilitating delivery of vaccine postexposure prophylaxis (PEP) and antivirals that have been stockpiled by the U.S. government for preparedness and response purposes. On May 19, a call center was established to provide guidance to states for the evaluation of possible cases of monkeypox, including recommendations for clinical diagnosis and orthopoxvirus testing. The call center also gathers information about possible cases to identify interjurisdictional linkages. As of May 31, this investigation has identified 17§ cases in the United States; most cases (16) were diagnosed in persons who identify as gay, bisexual, or men who have sex with men (MSM). Ongoing investigation suggests person-to-person community transmission, and CDC urges health departments, clinicians, and the public to remain vigilant, institute appropriate infection prevention and control measures, and notify public health authorities of suspected cases to reduce disease spread. Public health authorities are identifying cases and conducting investigations to determine possible sources and prevent further spread. This activity was reviewed by CDC and conducted consistent with applicable federal law and CDC policy.¶.

Reducing travel-related SARS-CoV-2 transmission with layered mitigation measures: symptom monitoring, quarantine, and testing.

BACKGROUND: Balancing the control of SARS-CoV-2 transmission with the resumption of travel is a global priority. Current recommendations include mitigation measures before, during, and after travel. Pre- and post-travel strategies including symptom monitoring, antigen or nucleic acid amplification testing, and quarantine can be combined in multiple ways considering different trade-offs in feasibility, adherence, effectiveness, cost, and adverse consequences. METHODS: We used a mathematical model to analyze the expected effectiveness of symptom monitoring, testing, and quarantine under different estimates of the infectious period, test-positivity relative to time of infection, and test sensitivity to reduce the risk of transmission from infected travelers during and after travel. RESULTS: If infection occurs 0-7 days prior to travel, immediate isolation following symptom onset prior to or during travel reduces risk of transmission while traveling by 30-35%. Pre-departure testing can further reduce risk, with testing closer to the time of travel being optimal even if test sensitivity is lower than an earlier test. For example, testing on the day of departure can reduce risk while traveling by 44-72%. For transmission risk after travel with infection time up to 7 days prior to arrival at the destination, isolation based on symptom monitoring reduced introduction risk at the destination by 42-56%. A 14-day quarantine after arrival, without symptom monitoring or testing, can reduce post-travel risk by 96-100% on its own. However, a shorter quarantine of 7 days combined with symptom monitoring and a test on day 5-6 after arrival is also effective (97--100%) at reducing introduction risk and is less burdensome, which may improve adherence. CONCLUSIONS: Quarantine is an effective measure to reduce SARS-CoV-2 transmission risk from travelers and can be enhanced by the addition of symptom monitoring and testing. Optimal test timing depends on the effectiveness of quarantine: with low adherence or no quarantine, optimal test timing is close to the time of arrival; with effective quarantine, testing a few days later optimizes sensitivity to detect those infected immediately before or while traveling. These measures can complement recommendations such as social distancing, using masks, and hand hygiene, to further reduce risk during and after travel.

Risk Assessment and Management of COVID-19 Among Travelers Arriving at Designated U.S. Airports, January 17-September 13, 2020.

In January 2020, with support from the U.S. Department of Homeland Security (DHS), CDC instituted an enhanced entry risk assessment and management (screening) program for air passengers arriving from certain countries with widespread, sustained transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). The objectives of the screening program were to reduce the importation of COVID-19 cases into the United States and slow subsequent spread within states. Screening aimed to identify travelers with COVID-19-like illness or who had a known exposure to a person with COVID-19 and separate them from others. Screening also aimed to inform all screened travelers about self-monitoring and other recommendations to prevent disease spread and obtain their contact information to share with public health authorities in destination states. CDC delegated postarrival management of crew members to airline occupational health programs by issuing joint guidance with the Federal Aviation Administration.* During January 17-September 13, 2020, a total of 766,044 travelers were screened, 298 (0.04%) of whom met criteria for public health assessment; 35 (0.005%) were tested for SARS-CoV-2, and nine (0.001%) had a positive test result. CDC shared contact information with states for approximately 68% of screened travelers because of data collection challenges and some states' opting out of receiving data. The low case detection rate of this resource-intensive program highlighted the need for fundamental change in the U.S. border health strategy. Because SARS-CoV-2 infection and transmission can occur in the absence of symptoms and because the symptoms of COVID-19 are nonspecific, symptom-based screening programs are ineffective for case detection. Since the screening program ended on September 14, 2020, efforts to reduce COVID-19 importation have focused on enhancing communications with travelers to promote recommended preventive measures, reinforcing mechanisms to refer overtly ill travelers to CDC, and enhancing public health response capacity at ports of entry. More efficient collection of contact information for international air passengers before arrival and real-time transfer of data to U.S. health departments would facilitate timely postarrival public health management, including contact tracing, when indicated. Incorporating health attestations, predeparture and postarrival testing, and a period of limited movement after higher-risk travel, might reduce risk for transmission during travel and translocation of SARS-CoV-2 between geographic areas and help guide more individualized postarrival recommendations.

US Federal Travel Restrictions for Persons with Higher-Risk Exposures to Communicable Diseases of Public Health Concern.

Published guidance recommends controlled movement for persons with higher-risk exposures (HREs) to communicable diseases of public health concern; US federal public health travel restrictions (PHTRs) might be implemented to enforce these measures. We describe persons eligible for and placed on PHTRs because of HREs during 2014-2016. There were 160 persons placed on PHTRs: 142 (89%) involved exposure to Ebola virus, 16 (10%) to Lassa fever virus, and 2 (1%) to Middle East respiratory syndrome coronavirus. Most (90%) HREs were related to an epidemic. No persons attempted to travel; all persons had PHTRs lifted after completion of a maximum disease-specific incubation period or a revised exposure risk classification. PHTR enforced controlled movement and removed risk for disease transmission among travelers who had contacts who refused to comply with public health recommendations. PHTRs are mechanisms to mitigate spread of communicable diseases and might be critical in enhancing health security during epidemics.

Conveyance Contact Investigation for Imported Middle East Respiratory Syndrome Cases, United States, May 2014.

In 2014, the Centers for Disease Control and Prevention conducted conveyance contact investigations for 2 Middle East respiratory syndrome cases imported into the United States, comprising all passengers and crew on 4 international and domestic flights and 1 bus. Of 655 contacts, 78% were interviewed; 33% had serologic testing. No secondary cases were identified.

Federal travel restrictions to prevent disease transmission in the United States: An analysis of requested travel restrictions.

BACKGROUND: Individuals with certain communicable diseases may pose risks to the health of the traveling public; there has been documented transmission on commercial aircraft of tuberculosis (TB), measles, and severe acute respiratory syndrome (SARS). Federal public health travel restrictions (PHTR) prevent commercial air or international travel of persons with communicable diseases that pose a public health threat. METHODS: We described demographics and clinical characteristics of all cases considered for PHTR because of suspected or confirmed communicable disease from May 22, 2007, to December 31, 2015. RESULTS: We reviewed 682 requests for PHTR; 414 (61%) actions were completed to place 396 individuals on PHTR. The majority (>99%) had suspected (n = 27) or confirmed (n = 367) infectious pulmonary TB; 58 (16%) had multidrug-resistant-TB. There were 128 (85%) interceptions that prevented the initiation or continuation of travel. PHTR were removed for 310 (78%) individuals after attaining noninfectious status and 86 (22%) remained on PHTR at the end of the analysis period. CONCLUSIONS: PHTR effectively prevent exposure during commercial air travel to persons with potentially infectious diseases. In addition, they are effective tools available to public health agencies to prevent commercial travel of individuals with certain communicable diseases and possibly reconnect them with public health authorities.

Update: Ongoing Zika Virus Transmission - Puerto Rico, November 1, 2015-July 7, 2016.

Zika virus is a flavivirus transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes, and infection can be asymptomatic or result in an acute febrile illness with rash (1). Zika virus infection during pregnancy is a cause of microcephaly and other severe birth defects (2). Infection has also been associated with Guillain-Barré syndrome (GBS) (3) and severe thrombocytopenia (4,5). In December 2015, the Puerto Rico Department of Health (PRDH) reported the first locally acquired case of Zika virus infection. This report provides an update to the epidemiology of and public health response to ongoing Zika virus transmission in Puerto Rico (6,7). A confirmed case of Zika virus infection is defined as a positive result for Zika virus testing by reverse transcription-polymerase chain reaction (RT-PCR) for Zika virus in a blood or urine specimen. A presumptive case is defined as a positive result by Zika virus immunoglobulin M (IgM) enzyme-linked immunosorbent assay (MAC-ELISA)* and a negative result by dengue virus IgM ELISA, or a positive test result by Zika IgM MAC-ELISA in a pregnant woman. An unspecified flavivirus case is defined as positive or equivocal results for both Zika and dengue virus by IgM ELISA. During November 1, 2015-July 7, 2016, a total of 23,487 persons were evaluated by PRDH and CDC Dengue Branch for Zika virus infection, including asymptomatic pregnant women and persons with signs or symptoms consistent with Zika virus disease or suspected GBS; 5,582 (24%) confirmed and presumptive Zika virus cases were identified. Persons with Zika virus infection were residents of 77 (99%) of Puerto Rico's 78 municipalities. During 2016, the percentage of positive Zika virus infection cases among symptomatic males and nonpregnant females who were tested increased from 14% in February to 64% in June. Among 9,343 pregnant women tested, 672 had confirmed or presumptive Zika virus infection, including 441 (66%) symptomatic women and 231 (34%) asymptomatic women. One patient died after developing severe thrombocytopenia (4). Evidence of Zika virus infection or recent unspecified flavivirus infection was detected in 21 patients with confirmed GBS. The widespread outbreak and accelerating increase in the number of cases in Puerto Rico warrants intensified vector control and personal protective behaviors to prevent new infections, particularly among pregnant women.

Tracing Airline Travelers for a Public Health Investigation: Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Infection in the United States, 2014.

OBJECTIVE: CDC routinely conducts contact investigations involving travelers on commercial conveyances, such as aircrafts, cargo vessels, and cruise ships. METHODS: The agency used established systems of communication and partnerships with other federal agencies to quickly provide accurate traveler contact information to states and jurisdictions to alert contacts of potential exposure to two travelers with Middle East Respiratory Syndrome Coronavirus (MERS-CoV) who had entered the United States on commercial flights in April and May 2014. RESULTS: Applying the same process used to trace and notify travelers during routine investigations, such as those for tuberculosis or measles, CDC was able to notify most travelers of their potential exposure to MERS-CoV during the first few days of each investigation. CONCLUSION: To prevent the introduction and spread of newly emerging infectious diseases, travelers need to be located and contacted quickly.

Travel and Border Health Measures to Prevent the International Spread of Ebola.

During the 2014-2016 Ebola virus disease (Ebola) epidemic in West Africa, CDC implemented travel and border health measures to prevent international spread of the disease, educate and protect travelers and communities, and minimize disruption of international travel and trade. CDC staff provided in-country technical assistance for exit screening in countries in West Africa with Ebola outbreaks, implemented an enhanced entry risk assessment and management program for travelers at U.S. ports of entry, and disseminated information and guidance for specific groups of travelers and relevant organizations. New and existing partnerships were crucial to the success of this response, including partnerships with international organizations, such as the World Health Organization, the International Organization for Migration, and nongovernment organizations, as well as domestic partnerships with the U.S. Department of Homeland Security and state and local health departments. Although difficult to assess, travel and border health measures might have helped control the epidemic's spread in West Africa by deterring or preventing travel by symptomatic or exposed persons and by educating travelers about protecting themselves. Enhanced entry risk assessment at U.S. airports facilitated management of travelers after arrival, including the recommended active monitoring. These measures also reassured airlines, shipping companies, port partners, and travelers that travel was safe and might have helped maintain continued flow of passenger traffic and resources needed for the response to the affected region. Travel and border health measures implemented in the countries with Ebola outbreaks laid the foundation for future reconstruction efforts related to borders and travel, including development of regional surveillance systems, cross-border coordination, and implementation of core capacities at designated official points of entry in accordance with the International Health Regulations (2005). New mechanisms developed during this response to target risk assessment and management of travelers arriving in the United States may enhance future public health responses. The activities summarized in this report would not have been possible without collaboration with many U.S. and international partners (http://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/partners.html).

Update: Ongoing Zika Virus Transmission - Puerto Rico, November 1, 2015-April 14, 2016.

Zika virus is a flavivirus transmitted primarily by Aedes species mosquitoes, and symptoms of infection can include rash, fever, arthralgia, and conjunctivitis (1).* Zika virus infection during pregnancy is a cause of microcephaly and other severe brain defects (2). Infection has also been associated with Guillain-Barré syndrome (3). In December 2015, Puerto Rico became the first U.S. jurisdiction to report local transmission of Zika virus, with the index patient reporting symptom onset on November 23, 2015 (4). This report provides an update to the epidemiology of and public health response to ongoing Zika virus transmission in Puerto Rico. During November 1, 2015-April 14, 2016, a total of 6,157 specimens from suspected Zika virus-infected patients were evaluated by the Puerto Rico Department of Health (PRDH) and CDC Dengue Branch (which is located in San Juan, Puerto Rico), and 683 (11%) had laboratory evidence of current or recent Zika virus infection by one or more tests: reverse transcription-polymerase chain reaction (RT-PCR) or immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA). Zika virus-infected patients resided in 50 (64%) of 78 municipalities in Puerto Rico. Median age was 34 years (range = 35 days-89 years). The most frequently reported signs and symptoms were rash (74%), myalgia (68%), headache (63%), fever (63%), and arthralgia (63%). There were 65 (10%) symptomatic pregnant women who tested positive by RT-PCR or IgM ELISA. A total of 17 (2%) patients required hospitalization, including 5 (1%) patients with suspected Guillain-Barré syndrome. One (<1%) patient died after developing severe thrombocytopenia. The public health response to the outbreak has included increased laboratory capacity to test for Zika virus infection (including blood donor screening), implementation of enhanced surveillance systems, and prevention activities focused on pregnant women. Vector control activities include indoor and outdoor residual spraying and reduction of mosquito breeding environments focused around pregnant women's homes. Residents of and travelers to Puerto Rico should continue to employ mosquito bite avoidance behaviors, take precautions to reduce the risk for sexual transmission (5), and seek medical care for any acute illness with rash or fever.

Border Lookout: Enhancing Tuberculosis Control on the United States-Mexico Border.

We evaluated the use of federal public health intervention tools known as the Do Not Board and Border Lookout (BL) for detecting and referring infectious or potentially infectious land border travelers with tuberculosis (TB) back to treatment. We used data about the issuance of BL from April 2007 to September 2013 to examine demographics and TB laboratory results for persons on the list (N = 66) and time on the list before being located and achieving noninfectious status. The majority of case-patients were Hispanic and male, with a median age of 39 years. Most were citizens of the United States or Mexico, and 30.3% were undocumented migrants. One-fifth had multidrug-resistant TB. Nearly two-thirds of case-patients were located and treated as a result of being placed on the list. However, 25.8% of case-patients, primarily undocumented migrants, remain lost to follow-up and remain on the list. For this highly mobile patient population, the use of this novel federal travel intervention tool facilitated the detection and treatment of infectious TB cases that were lost to follow-up.

Public health response to commercial airline travel of a person with Ebola virus infection - United States, 2014.

Before the current Ebola epidemic in West Africa, there were few documented cases of symptomatic Ebola patients traveling by commercial airline, and no evidence of transmission to passengers or crew members during airline travel. In July 2014 two persons with confirmed Ebola virus infection who were infected early in the Nigeria outbreak traveled by commercial airline while symptomatic, involving a total of four flights (two international flights and two Nigeria domestic flights). It is not clear what symptoms either of these two passengers experienced during flight; however, one collapsed in the airport shortly after landing, and the other was documented to have fever, vomiting, and diarrhea on the day the flight arrived. Neither infected passenger transmitted Ebola to other passengers or crew on these flights. In October 2014, another airline passenger, a U.S. health care worker who had traveled domestically on two commercial flights, was confirmed to have Ebola virus infection. Given that the time of onset of symptoms was uncertain, an Ebola airline contact investigation in the United States was conducted. In total, follow-up was conducted for 268 contacts in nine states, including all 247 passengers from both flights, 12 flight crew members, eight cleaning crew members, and one federal airport worker (81 of these contacts were documented in a report published previously). All contacts were accounted for by state and local jurisdictions and followed until completion of their 21-day incubation periods. No secondary cases of Ebola were identified in this investigation, confirming that transmission of Ebola during commercial air travel did not occur.

Airport exit and entry screening for Ebola--August-November 10, 2014.

In response to the largest recognized Ebola virus disease epidemic now occurring in West Africa, the governments of affected countries, CDC, the World Health Organization (WHO), and other international organizations have collaborated to implement strategies to control spread of the virus. One strategy recommended by WHO calls for countries with Ebola transmission to screen all persons exiting the country for "unexplained febrile illness consistent with potential Ebola infection." Exit screening at points of departure is intended to reduce the likelihood of international spread of the virus. To initiate this strategy, CDC, WHO, and other global partners were invited by the ministries of health of Guinea, Liberia, and Sierra Leone to assist them in developing and implementing exit screening procedures. Since the program began in August 2014, an estimated 80,000 travelers, of whom approximately 12,000 were en route to the United States, have departed by air from the three countries with Ebola transmission. Procedures were implemented to deny boarding to ill travelers and persons who reported a high risk for exposure to Ebola; no international air traveler from these countries has been reported as symptomatic with Ebola during travel since these procedures were implemented.

First confirmed cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in the United States, updated information on the epidemiology of MERS-CoV infection, and guidance for the public, clinicians, and public health authorities - May 2014.

Since mid-March 2014, the frequency with which cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection have been reported has increased, with the majority of recent cases reported from Saudi Arabia and United Arab Emirates (UAE). In addition, the frequency with which travel-associated MERS cases have been reported and the number of countries that have reported them to the World Health Organization (WHO) have also increased. The first case of MERS in the United States, identified in a traveler recently returned from Saudi Arabia, was reported to CDC by the Indiana State Department of Health on May 1, 2014, and confirmed by CDC on May 2. A second imported case of MERS in the United States, identified in a traveler from Saudi Arabia having no connection with the first case, was reported to CDC by the Florida Department of Health on May 11, 2014. The purpose of this report is to alert clinicians, health officials, and others to increase awareness of the need to consider MERS-CoV infection in persons who have recently traveled from countries in or near the Arabian Peninsula. This report summarizes recent epidemiologic information, provides preliminary descriptions of the cases reported from Indiana and Florida, and updates CDC guidance about patient evaluation, home care and isolation, specimen collection, and travel as of May 13, 2014.

US screening of international travelers for radioactive contamination after the Japanese nuclear plant disaster in March 2011.

On March 11, 2011, a magnitude 9.0 earthquake and subsequent tsunami damaged nuclear reactors at the Fukushima Daiichi complex in Japan, resulting in radionuclide release. In response, US officials augmented existing radiological screening at its ports of entry (POEs) to detect and decontaminate travelers contaminated with radioactive materials. During March 12 to 16, radiation screening protocols detected 3 travelers from Japan with external radioactive material contamination at 2 air POEs. Beginning March 23, federal officials collaborated with state and local public health and radiation control authorities to enhance screening and decontamination protocols at POEs. Approximately 543 000 (99%) travelers arriving directly from Japan at 25 US airports were screened for radiation contamination from March 17 to April 30, and no traveler was detected with contamination sufficient to require a large-scale public health response. The response highlighted synergistic collaboration across government levels and leveraged screening methods already in place at POEs, leading to rapid protocol implementation. Policy development, planning, training, and exercising response protocols and the establishment of federal authority to compel decontamination of travelers are needed for future radiological responses. Comparison of resource-intensive screening costs with the public health yield should guide policy decisions, given the historically low frequency of contaminated travelers arriving during radiological disasters.

Deaths in international travelers arriving in the United States, July 1, 2005 to June 30, 2008.

BACKGROUND: The Centers for Disease Control and Prevention's (CDC) Quarantine Activity Reporting System (QARS), which documents reports of morbidity and mortality among travelers, was analyzed to describe the epidemiology of deaths during international travel. METHODS: We analyzed travel-related deaths reported to CDC from July 1, 2005 to June 30, 2008, in which international travelers died (1) on a U.S.-bound conveyance, or (2) within 72 hours after arriving in the United States, or (3) at any time after arriving in the United States from an illness possibly acquired during international travel. We analyzed age, sex, mode of travel (eg, by air, sea, land), date, and cause of death, and estimated rates using generalized linear models. RESULTS: We identified 213 deaths. The median age of deceased travelers was 66 years (range 1-95); 65% were male. Most deaths (62%) were associated with sea travel; of these, 111 (85%) occurred in cruise ship passengers and 20 (15%) among cargo and cruise ship crew members. Of 81 air travel-associated deaths, 77 occurred in passengers, 3 among air ambulance patients, and 1 in a stowaway. One death was associated with land travel. Deaths were categorized as cardiovascular (70%), infectious disease (12%), cancer (6%), unintentional injury (4%), intentional injury (1%), and other (7%). Of 145 cardiovascular deaths with reported ages, 62% were in persons 65 years of age and older. Nineteen (73%) of 26 persons who died from infectious diseases had chronic medical conditions. There was significant seasonal variation (lowest in July-September) in cardiovascular mortality in cruise ship passengers. CONCLUSIONS: Cardiovascular conditions were the major cause of death for both sexes. Travelers should seek pre-travel medical consultation, including guidance on preventing cardiovascular events, infections, and injuries. Persons with chronic medical conditions and the elderly should promptly seek medical care if they become ill during travel.