For the most part, little is known about emerging pathogens before they emerge so, frequently, viruses from zoonotic sources that are unrecognized present a unique challenge to science and medicine. A zoonosis is an infection caused by bacteria, viruses, parasites, or fungi transferred from a non-human animal to humans. 1 Zoonotic transmission may be due to a spillover event from an animal to a human, which is caused by a sustained or new close human contact or by climate changes that affect the distribution of disease vectors, e.g.; insects that have been previously restricted geographically through the effects of climate changes. Evolution of a pathogen that has been previously animal-restricted can cause a virus to emerge-one that is capable of utilizing a human receptor or the cellular machinery needed to cause infection. 2 Coronaviruses (CoVs) are large enveloped, positive strand RNA viruses. These viruses fall into four genera: alpha, beta, delta, and gamma. The two CoV subtypes known to affect humans (HCoVs) are alpha and beta. Four HCoVs including HCoV229E, NL63, OC43, and HKU1 account for 10%-30% of adult respiratory infections and are endemic globally. The ecologically diverse coronavirus occurs most prevalently in bats which serve as a host reservoir. 3 The mild types of CoVs in humans, which cause the common cold, gained little attention until 2002 when the virus emerged from Guangdong Province, China causing cases of severe atypical pneumonia. This disease, which became known as SARS, or severe acute respiratory syndrome, caused world-wide concern when it spread to 37 countries. 4 The causative agent was SARS-CoV and bats were determined to be the zoonotic reservoir. Subsequent transmission to humans transpired from civets (an Asian animal related to the mongoose and weasel) which had become infected by a bat. 4, 5 Globally, this virus affected more than 8,000 people and had a 10% fatality rate. 6 Following SARS, MERS-CoV emerged in 2012 from the Middle Eastern Arabian Peninsula.
Like SARS, the origin host for MERS-CoV is the bat but the transmitting animal is typically the dromedary camel. The virus has infected 1728 people, since its emergence, and has had a 35.6% mortality rate since August of 2016. 7 Recently, in December of last year, coronavirus re-emerged, once again from China, with the initial outbreak in Wuhan, a city located in the country's Hubei Province. It has since been designated as SARS-CoV-2 and the resulting disease is called COVID-2019 8 . Close to 300,000 cases, globally, have been reported, since its outbreak. The point of origin is considered to be a seafood/animal market in Wuhan which houses and sells, not only fish, but exotic animals including hedgehogs, badgers, snakes, and birds (turtledoves). 8, 9 This new virus, like the SARS and MERS coronaviruses, is also a beta subtype and its exact animal host/reservoir has yet to be determined. However, the World Health Organization (WHO) has reported that environmental samples taken from the marketplace came back positive for COVID-2019. Its similarity to SARS is found in the predominant human receptor for the SARS S glycoprotein, human angiotensinconverting enzyme 2 (ACE2), which is found primarily in the lower respiratory tract, rather than in the upper airway. 3 This may be a partial explanation for the severe respiratory symptoms and consequences of both diseases including acute respiratory distress syndrome (ARDS). When cases were being confirmed in people who had not visited the Wuhan seafood market or been in its proximity, suspicions arose that the virus was being transmitted from person to person. 10 A study published by the New England Journal of Medicine of the first 435 patients that were infected with the new virus, in Wuhan, found that the median age was 59 years old (range of 15-89 yrs.), 56% were male, and that no children < 15yrs had contracted the disease. 11 Since this study, however, a retrospective study at Wuhan University that was published in JAMA has reported that 9 infants had contracted COVID-2019 ranging in age from 1-11mos. of which seven were female. 12 The first confirmed U.S. case of COVID-2019 was diagnosed in the state of Washington, on January 30, 2020, resulting from person to person contact, and was it determined to be caused through international travel to Wuhan, China. 13 This, also, is the date the rapidly spreading virus was declared a public health emergency of international concern (PHEIC) by the International Health Regulations (IHR) emergency committee of the WHO. PHEIC is defined by the WHO as "an extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease; and to potentially require a coordinated international response." This definition implies a situation that: "is serious, unusual, or unexpected; carries implications for public health beyond the affected State's national border;
and may require immediate international action." Declaring a PHEIC expands the WHO's authority to coordinate a response in various ways, including through the issuance of recommendations on whether countries should impose trade and travel restrictions. 10 epicenter has confirmed 81,601 cases with 3276 fatalities to date. 8,10 Global mortality rate so far is at 4.4%, a much lower rate than the SARS and MERS viruses at this point in time. Daily updated statistics can be found at the CDC and WHO websites. Some cities, states and complete countries have been forced to shelter in place in an effort to prevent further spread. COVID-2019 has not, as of yet, peaked according to public health authorities with the ultimate scope and effects of the outbreak remaining to be seen. The number of confirmed cases has far surpassed those of both SARS and MERS combined-placing an astounding strain on health care systems.
The CDC recommendations for international travel from the U.S. can be found on its website.
Ultimately, international travel is not recommended, if it is not essential, and postponement of any nonessential international travel should, especially, be considered by older adults and those with chronic medical conditions (CDC Warning Level 3). 8
Transmission Although the origin of the COVID-2019 is zoonotic, current epidemiologic data demonstrate that human transmission is occurring. 8, 10, 18 It is thought to spread through respiratory droplets resulting from a cough or sneeze of an infected person that reaches people who are in close contact i.e.; people who are 6 feet or less apart. Transmission may occur through a person who has contact with infected surfaces or objects who then touch their eyes, nose or mouth but this, as yet, has not been considered a frequent route of transmission for this particular coronavirus. The COVID-2019 virus appears to spread most from a person who is at the peak of their symptoms.
It has been suspected that it is spread as well from persons infected with the virus who are not yet exhibiting symptoms. 8 The incubation period has been determined to be 2-14 days.
Transmission of the disease remains easy and sustainable in Hubei Province and in other parts of China and now has a similar spread in many other countries. CDC issued a statement on February 25, 2020 that spread was expected to occur in the U.S. and, this has since proven to be the case.
Clinical stigmatization is a phenomenon which may occur with an infectious disease. In the case of COVID people may associate it, in general, with the Chinese population. Stigmatization would occur for example when a Chinese American, living in the U.S., is associated with the virus. 8
Predominant clinical symptoms are fever, dry cough, and shortness of breath. 5, 8, 10, 15, 16, 17, 18 Ten percent of patients have presented with nausea and diarrhea 1-2 days prior to development of fever and dyspnea in a retrospective study in a Wuhan, China hospital. Upon imaging examination, 74 (75%) patients in this same cohort showed bilateral pneumonia. 5 As with SARS and MERS, a large number of patients have exhibited symptoms of viral pneumonia including fever, difficulty breathing, and in the most severe cases bilateral infiltrates. 16 Patients admitted to ICU were older adults and those who had comorbid conditions-suggesting a poor outcome. 5 Complications, in addition to pneumonia, included respiratory failure, ARDS, cardiac injury, shock, kidney injury, and fatal outcomes. 5, 17 Pregnant women, because they are in an immunosuppressive state that causes adaptive changes such as diaphragm elevation, increased oxygen consumption, and edema of respiratory mucosa, are particularly susceptible to respiratory pathogens. Severe pneumonia can render these women intolerant to hypoxia 19 Management of patients who test positive during pregnancy and have no symptoms is similar to the general population in that self-monitoring at home is recommended for 14 days. These patients, as well as those self-monitoring for mild illness from the disease, due to the potential risk of intrauterine growth restriction, should have fetal growth ultrasounds and doppler assessments bimonthly. Pregnant women with COVID-2019 related pneumonia should be cared for in a tertiary care center by a multi-disciplinary team. 26 Women who test positive for COVID-2019 at delivery may safely breastfeed their newborns. 8
The best way to prevent illness from COVID-2019, since there is no current vaccine, is to avoid being exposed to this virus. The CDC recommends everyday preventive actions to help prevent the spread of respiratory disease, including avoiding close contact with people who are sick, covering your cough or sneeze, avoidance of touching eyes, nose, and mouth, washing hands often with soap or alcohol-based hand sanitizers, and not wearing a face mask if you are well.
Masks are not recommended for healthy persons for protection from the disease unless there is known exposure. 8
The Role of Primary Care Providers Indispensable tools for the detection and monitoring of outbreaks and public health emergencies include strong epidemiology and surveillance systems, however, strong primary care systems can form the foundation of any emergency response. Member states of WHO have shown a consistent commitment to training community-based health professionals who then become capable of providing care across the spectrum of prevention, preparedness, response, and recovery, which further develops primary care. Often considered the 'front door' of the healthcare system primary care should be involved in planning and action for health emergency risk management 27 . It is important that there is close coordination between clinicians and public health authorities at the local, state, and federal level. From a clinical perspective, when a patient presents with fever and respiratory symptoms (in particular a dry cough), clinicians should obtain a detailed travel history. CDC guidelines for health care professionals for evaluating patients' epidemiological risks, in conjunction with the characteristic symptoms of COVID-2019 can be found on its website. When symptoms, travel history, and relevant illness exposure raises suspicion for COVID-2019, the state or local health department should be immediately notified.
This person becomes a person under investigation (PUI) and should be placed in isolation and infection control personnel, if applicable, for the facility should be notified immediately.
Healthcare staff who are in contact with the patient should utilize PPE precautions. If, and when testing is done, testing personnel should wear an N95 respirator mask as discussed in the diagnosis/evaluation section. In the severely ill individual, testing can be considered, as previously mentioned, when another etiology has not been identified and exposure history is equivocal (e.g., uncertain travel or exposure, or no known exposure). Slowing U.S. transmission of COVID-2019 is critical and the fact that primary care providers play an important role has already become evident, since the December emergence of this virus. This has been demonstrated by the detection of eight of the first eleven U.S. cases by clinicians who then collaborated with public health officials to test persons at risk. 28 Both early recognition and an increased understanding of the virus by health care providers can reduce transmission. 27 
The Wuhan emergence of the third coronavirus this century is a stark reminder of the continuing threat of zoonotic diseases to global health security. There is increasing international concern regarding its continued spread. The rapid identification and containment of this virus by China's public health authorities reflects the increasing global capacity to detect, identify, and define new outbreaks. 29 The disease has met all three criteria for a pandemic: 1). Caused by an illness and fatalities are related to this illness; 2). has had sustained person to person spread, and recently; 3) worldwide spread. . 8 A concerted and collaborative global effort, based on sharing experiences from all geographical regions and all disciplines, should continue to be led and coordinated by the WHO with an emphasis placed on containment, surveillance, and prevention in addition to rapid dissemination of clinical information related to the care of patients with this infection. This effort can start with early detection of the virus by primary health care providers through an awareness of COVID 2019 characteristics and recognition of possible cases, which is then followed by, if needed, coordination with public health systems. The key to sustaining and further development of the progress being made toward the management and containment of COVID-2019 is the sharing of experiences and knowledge garnered from all geographical regions and across all disciplines. 27 The perpetual challenge of emerging infections and the importance of sustained preparedness has been underscored by a novel coronavirus from which pathogens have caused a global human disease.