Other human Coronaviruses: close, but still so far

Publicação: 11 de April de 2020

People around the world are generally infected with human coronavirus 229E, NL63, OC43 and HKU1 throughout their lives

Alpha coronavirus 229E and NL63 are more common, and children are more prone to infection, whereas Beta coronavirus OC43 circulates among humans, but is not investigated in the laboratory routine

Coronaviruses BELONG TO a large viral family that causeS respiratory infections in humans and OTHER animals. The first coronavirus-associated disease was reported in 1937 in chckens. However, it was only described as a coronavirus in 1965, when profile analysis under microscopy revealed its appearance. The most regular types that infect humans are Alphacoronaviruses 229E and NL63 and the Betacoronaviruses OC43 and HKU1. We also have SARS-CoV-1, MERS-CoV and now SARS-CoV-2 (the new coronavirus that causes COVID-19). People around the world are generally infected with human coronaviruses throughout their lives, and very rarelly the coronaviruses that infect other animals can evolve and make people sick and become a new human coronavirus. Three recent examples of this are SARS-CoV-2, SARS-CoV-1 and MERS-CoV.

Of the seven known varieties, four have already been identified in Brazil. The virologist Paulo Eduardo Brandão, from the Department of Preventive Veterinary Medicine and Animal Health at the School of Veterinary Medicine at the University of São Paulo, explains that prior to the finding of Sars-CoV-2 this year in Brazil, there was already the presence of the exclusively humans coronaviruses OC-43, 229E, NL63 and HKU1, all with tropism for the respiratory tract and etiological agents of less severe respiratory processes when compared to COVID-19..

According to Dr. Brandão, considering the coronaviruses that infect humans, in Brazil, only MERS-CoV, involved in Middle East respiratory syndrome (MERS), and Sars-CoV-1, from Severe accute respiratory syndrome (SARS), were not found. “MERS-CoV and Sars-CoV-1 infections are more aggressive and dangerous, considering the lethalities of approximately 35 and 10%, respectively”, he highlights. SARS-CoV-1 spread rapidly to more than twelve countries in North America, South America, Europe and Asia, infecting more than 8. thousand people and caused about 800 deaths, before the global SARS epidemic was stopped in 2003. In 2012, another new coronavirus was isolated, distinct from the one that caused SARS at the beginning of the past decade. This new coronavirus was unknown as an agent of human disease until its identification, initially in Saudi Arabia and, later, in other countries in the Middle East, Europe and Africa. All cases identified outside the Arabian Peninsula had a history of travel or recent contact with travelers from countries in the Middle East – Saudi Arabia, Qatar, the United Arab Emirates and Jordan. Due to the location of the cases, the disease came to be designated as Middle East respiratory syndrome, and the new virus named MERS-associated coronavirus (MERS-CoV).

The betacoronavirus OC43, for example, was found in the laboratory in Pernambuco. Between April 2008 and March 2009, the study “Viral and atypical bacterial detection in acute respiratory infection in children under five years old, conducted in Instituto de Medicina Integral Professor Fernando Figueira (Imip), by pediatric pulmonologist Patrícia Bezerra, detected that coronaviruses were found in 3.2% of the samples, with OC43 being the most common (1.7%). The virus circulates among humans, but is not investigated in the laboratory routine. It causes a common cold and, therefore, is only investigated when research is carried out or when an outbreak (of respiratory viruses) is in effect. Alphacoronaviruses 229E and NL63 are more common, and children are more likely to become infected with this type of virus. HKU1, the most demanding human coronavirus identified to date, was discovered in 2005.

How coronaviruses arrived in Brazil

Sars-CoV-2 arrived with people infected in Europe who traveled to Brazil. Coronaviruses in animal species other than humans probably came together with the introduction of their hosts in the country, such as dogs, cats, cattle, chickens, etc. “But bat species probably already had their own coronaviruses here”, says Dr. Brandão, adding that birds and mammals have an immense diversity of coronavirus species, which are host-specific, which making cases of jumps between host species a rare episode. Still according to him, the coronavirus in general has double respiratory-enteric tropism, but some species of this virus, such as more virulent biotypes of canine and feline coronavirus, are pantropic. Others, such as avian Coronavirus, have a vast antigenic diversity, which makes it difficult to control them through vaccination.

Coronavirus from dogs, cats, birds, and the others previously mentioned about other animals do not infect humans because they use different receptors. The same is true for human coronaviruses, which do not infect other species. The greatest risk of transmission to people is through direct aerosol contagion”, says the veterinarian. As Brazil has its own varieties of wild coronaviruses, the expert warns that attention should be paid to coronaviruses found in bats, a fact that has already been documented in Brazil. Asked about the possibility of them passing from animals to people, what can happen, Dr. Brandão is categorical in stating that studies in genomics, evolution and pathogenesis for these bat coronaviruses will bring these answers. “Regarding the varieties that have not yet been found in Brazil yet to reach the country, the veterinarian is reassured when he remembers that Sars-CoV-1 has disappeared since 2004, no other case has been reported worldwide in recent years, and MERS-CoV is more restricted to the Middle East. Thus, the probability of being introduced in Brazil is very low.

Finally, Dr. Brandão warns that other coronaviruses and other viruses will appear. “There is no other way out than investing in Science, training scientists in Virology, Public Health, Epidemiology, Bioinformatics etc. and forming networks of laboratories before and not after their emergence”, he argues.

Coronavirus alone or associated with another virus is a risk factor for respiratory disease

The publication entitled “First detection of human coronavirus associated with acute respiratory infection in the Northern Region of Brazil reports the circulation of the coronavirus (CoVh) in Belém (PA) in the period from August 2009 to March 2011. According to the study, samples of nasopharyngeal aspirate or combined swab (nasal and oral) obtained from 308 patients with a clinical diagnosis of acute respiratory infection (ARI), were laboratory investigated for evidence of CoVh infection. This was the first work of its kind conducted in the Northern Region of Brazil. “Despite the low incidence of this virus, its high pathogenic capacity cannot be disregarded, since it has been listed as one of the pathogens associated with ARF and its clinical complications”, emphasized the research.

In São Luís (MA), the varieties HCoV OC43 and NL63 were identified respectively in 3.1% and 1.5% of a group of 150 children aged between 3 months and 10 years hospitalized with pneumonia caused by these and others virus between November 2014 and April 2016 in two public hospitals: Children’s Hospital Dr. Odorico de Amaral Matos and Children’s Hospital Dr. Juvêncio Mattos. The publication “High incidence of rhinovirus infection in children with communityacquired pneumonia from a city in the Brazilian preAmazon region” can be accessed here.

In Paraná, a team from the Federal University of Paraná (UFPR) identified the four human coronavirus subtypes in 7.6% of 444 children and adults admitted to the Hospital das Clínicas at UFPR with severe respiratory infection in 2012 and 2013. The full publication can be accessed here.

Slum populations, on the other hand, stand out from other contexts and may differ in the epidemiology of acute viral infections. Between 2005 and 2006, nasopharyngeal samples were collected from 282 children under 5 years of age with acute respiratory tract infection in one of the largest Brazilian slums. The publication “Typical epidemiology of respiratory virus infections in a Brazilian slum” can be accessed here.

The publication “Human coronavirus alone or in co-infection with rhinovirus C is a risk factor for severe respiratory disease and admission to the pediatric intensive care unit: A one-year study in Southeast Brazil, in turn, evaluated the profile of respiratory viruses in young children hospitalized for acute lower respiratory tract infection and its association with the severity of the disease, defined as the need admission to a pediatric intensive care unit.