Most frequent signs and symptoms among confirmed COVID-19 cases

Ten studies were selected which describe the first confirmed COVID-19 cases and the most common signs and symptoms found. The studies are summarized in Table 1 .

According to the Brazilian Ministry of Health, information is still limited for characterizing the spectrum of the clinical disease. The Ministry therefore establishes flu-like syndrome (FS) as being the most common manifestation, this being defined as an acute respiratory clinical picture, characterized by sensation of fever or fever, even if reported, accompanied by coughing, sore throat or runny nose or difficulty in breathing. ⁷ If breathing difficulties are present, severe acute respiratory syndrome (SARS) may be considered, ⁸ defined by FS showing dyspnea/breathing discomfort or persistent pressure in the thorax or O ₂ saturation below 95% in ambient air or lips or face with a bluish color. ⁹

According to the World Health Organization (WHO), ² the initial signs/symptoms of the disease appear like those of influenza, but vary from person to person, and can be mild, in the form of pneumonia, severe pneumonia and SARS. The majority of infected people have the mild form of the disease, with symptoms such as malaise, fever, tiredness, coughing, mild dyspnea, anorexia, sore throat, aching body, headache or blocked nose, some may also have diarrhea, nausea and vomiting. Signs and symptoms in elderly and immunocompromised people may be atypical and worsen rapidly, which can cause death, especially in the case of the elderly and people with pre-existing comorbidities.

The case definitions adopted by the Brazilian Health Ministry were established in February ¹⁰ and March 2020, ⁷ as detailed in Figure 1 . Suspect case definitions were initially based on the occurrence of fever and at least one respiratory sign or symptom, with a history of the person having traveled to places with local transmission or contact with a confirmed case. ¹¹ However, fever is not necessarily present in all affected individuals, ⁷ considering that elderly people or even people with no comorbidities have not presented this specific sign. Moreover, the criterion for defining fever is not standardized, whereby it can be measured as temperature ≥37.5ºC, ¹² temperature ≥37.8ºC, ⁷ recorded on medical records for hospitalized cases ¹³ or even reported by the individual without confirmation by measuring their temperature. ⁷

Legend: COVID-19, diseases caused by Sars-CoV-2; EB, Brazilian Health Ministry Epidemiological Bulletin.

Figure 1 – COVID-19 case definitions adopted in Brazil, 2020 

Be that as it may, the most common signs and symptoms are considered to be fever (temperature ≥37.8ºC), coughing, dyspnea (breathing difficulty), myalgia and fatigue. ¹¹ A study of 41 confirmed cases in China identified that 98% of them had fever, followed by coughing (76%), dyspnea (55%) and myalgia/fatigue (44%). ¹⁴ Wang et al. ¹⁵ described 69 cases in China and identified that some 15% of individuals analyzed had fever, coughing and dyspnea. A case report in Seattle, United States, ¹³ showed that 50% of cases did not have fever and that coughing and dyspnea were the most reported symptoms, accounting for 88% of cases. In a systematic review of clinical, laboratory and image findings for confirmed COVID-19 cases, ¹⁶ the most common clinical manifestations were fever (88.7% [95%CI 84.5; 92.9%]), coughing (57.6% [95%CI 40.8; 74.4%]) and dyspnea (45.6% [95%CI 10.9; 80.4%]), although they may not be present. Prevalence of fever was greater in adults than in children. ¹⁶

There are also reports of less common symptoms that are hard to measure objectively, such as anosmia (loss of sense of smell), hyposmia (reduction in sense of smell) and ageusia (loss of sense of taste). Specialist organizations propose that anosmia, hyposmia and ageusia should be included as part of screening for SARS-CoV-2 infection, principally in the absence of other respiratory diseases, such as allergic rhinitis and acute or chronic rhinosinusitis. ¹⁷ There is evidence of a significant number of people who developed these symptoms and later had positive COVID-19 test results. ¹⁸ A study with hospitalized individuals who tested positive for COVID-19 in Italy ¹⁹ found that 33.9% of them had either changes to sense of smell or taste while 18.6% had changes to both. Loss of sense of taste occurred in 91% before they were hospitalized. These symptoms were more frequently reported by women (52.6% versus 25%) and by less elderly people (median of 56 years, IQR 47-60 years versus 66 years, IQR 52-77). In Germany, anosmia was found in more than two thirds of individuals studied, while Italian and Swiss doctors are reporting similar symptoms, with many also having ageusia. In South Korea, anosmia was the main symptom in 30% of respondents with COVID-19. ¹⁸

In a cross-sectional study with 204 laboratory-confirmed cases in China, ²¹ gastrointestinal symptoms were reported by 50.5% at the time they were admitted to hospital, in addition to fever and respiratory symptoms. Their symptoms included ageusia, reported by 78.6% of cases, diarrhea in 34% of cases, as well as vomiting (3.9%) and abdominal pain (1.9%). In a retrospective study conducted in the Chinese Province of Zhejiang, ²² with 651 people hospitalized with diagnosis of COVID-19, 11.4% had gastrointestinal symptoms when they were admitted to hospital. The most prevalent digestive symptoms were diarrhea (71.62%), vomiting (14.86%) and nausea (13.51%).

Diagnosis criteria

In the document entitled Guidelines for COVID-19 Diagnosis and Treatment , given the inespecificity and heterogeneity of clinical presentation, the Ministry of Health considers a confirmed case to be a case with conclusive laboratory confirmation of SARS-CoV-2, regardless of signs or symptoms. ¹¹ However, in the absence of confirmatory diagnostic tests for all suspect cases, health services have had to adopt a very sensitive suspect case definition, especially for cases with mild symptoms, considering the symptoms reported by individuals, in view of the recommendation for people not to go to hospitals or health centers for clinical evaluation, in the absence of breathing discomfort as a sign of the disease becoming worse. ⁸

As such, using the clinical/epidemiological criterion, a suspect FS or SARS case is considered to be when there is a history of close or household contact with a laboratory confirmed COVID-19 case during the seven days prior to onset of symptoms and when it was not possible to perform specific laboratory investigation. As such, any flu-like symptom has been considered to indicate a suspect case, above all with the aim of individual isolation so as to avoid virus transmission. Notwithstanding, it is known that the majority of these cases considered to be suspect will not be confirmed, unless they get worse and need to be hospitalized, or voluntarily have rapid tests available in some places.

According to the Ministry of Health, stratification of the severity of suspect FS cases should take place during a medical consultation, indicating that mild cases (without dyspnea or signs and symptoms of severity) can be accompanied completely by Primary Health Care and Family Health Strategy (PHC/FHS) services in view of these cases being less severe. ⁸ Those who have FS with dyspnea or signs and symptoms of severity, or together with comorbidities that contraindicate home isolation, need stabilization at in PHC/FHS services and referral to Reference/Urgency/Hospital centers for 24-hour observation or interventions involving greater technological density. For these people who seek care at a health service facility, suspect findings in laboratory tests and in images can be used as indications of the disease, assisting with suspect case diagnosis. ¹⁶

Molecular tests, such as reverse transcription polymerase chain reaction (RT-PCR), which identify SARS-CoV-2 virus RNA, should be used between the 3 ^rd and 7 ^th day of symptoms using nasopharyngeal secretion samples, in order to ensure greater precision of the method and to reduce false-negative results. ²⁴ Due to the high cost and scarcity of laboratories authorized to perform them, RT-PCR tests are used for hospitalized symptomatic individuals and health workers. Immunochromatographic serological tests, known as rapid tests, have become an option for people with light to moderate symptoms who do not require hospitalization; for the general population, when screening asymptomatic cases; ⁶ and for observing immunity/recovery of confirmed cases. In this case, rapid tests should be used after seven days following onset of symptoms. ²⁵

Development of a serological response to virus infection depends on the host and takes time. In the case of SARS-CoV-2, initial studies suggest that the majority of cases seroconvert between 7 and 11 days following exposure to the virus. As a result of this natural delay, an antibody test may not be useful in the case of acute disease or for early assessment of infection. Moreover, the sensitivity and specificity of serological tests varies according to the manufacturer. In general, the sensitivity of the tests approved in Brazil by the National Health Surveillance Agency (ANVISA) was greater than 85%, and specificity was greater than 94%. ⁴ It is important to highlight that diagnostic tests with low sensitivity can result in a higher proportion of false-negative results, and this could interfere in the social isolation measures adopted, principally for asymptomatic individuals, thus having a direct influence on virus transmissibility.

As such, SARS-CoV-2 antibody tests can facilitate contact screening; serological surveillance at the local, regional, state and national level; and identification of those who have already been exposed and may possibly be immune, considering the existence of protective immunity.

Characteristics of case severity

Some COVID-19 cases have serious complications, leading to the need for care in intensive therapy units (ITU) or even leading to death. According to the Ministry of Health, besides the percentage of asymptomatic cases, among those who have COVID-19, around 80% are mild cases, 14% are severe cases and 5% are critical cases. ⁷ As for more complex cases, they either progress from the initial symptoms mentioned above, or they already manifest SARS-CoV-2 infection through SARS, by having dyspnea or clinical signs such as reduction in saturation or cyanosis. ⁸ In addition to the higher mortality rate due to SARS, there is also a group considered to be at risk because of greater lethality. Those belonging to this group are: elderly people aged 60 and over, high-risk pregnant women and people with a variety of comorbidities. ⁹ As such, individuals of all ages who have chronic diseases related to the lungs, asthma, those who currently have tuberculosis or sequelae of previous tuberculosis, diabetes, hypertension, severe obesity, chronic kidney disease, liver disease, immunodeficiency and heart problems also belong to the risk group. Recent studies ¹² report diabetes mellitus , systemic arterial hypertension, cerebrovascular disease and age as more decisive risk factors in relation to hospitalization in ITUs and death.

A retrospective study that assessed neurological aspects of confirmed COVID-19 cases ²⁹ indicated that 41.1% were considered severe. Compared to the milder cases, the severe cases were older individuals (58.7 ± 15.0 years versus 48.9 ± 14.7 years), had more comorbidities (42 [47.7%] versus 41 [32.5%]), especially hypertension (32 [36.4%] versus 19 [15.1%]), and had fewer symptoms considered to be typical, such as fever (40 [45.5%] versus 92 [73%]) and coughing (30 [34.1%] versus 77 [61.1%]).

Another study that described the characteristics of cases that died compared to cases that recovered ³⁰ found at least one chronic disease with greater frequency among cases that died (63% of those who died and 39% of those who recovered), whereby the main diseases were: systemic arterial hypertension (48%), cardiovascular diseases (14%) and cerebrovascular diseases (4%), versus 24%, 4% and 0%, respectively, in recovered cases. The following were also found to be more frequent among those who died: dyspnea (62% versus 31%), tight chest (49% versus 30%) and loss of consciousness (22% versus 1%); lymphopenia (39%) and leukocytosis (50%) ( versus 5% and 4% of those who recovered, respectively), saturation ≤93% (64% versus 12%), tachycardia (50% versus 30%) and tachypnea (27% versus 3%), as well as complications that can arise from the length of time spent in ITUs and the need for invasive procedures.

The study conducted by Wang et al. ¹⁵ assessed 69 people with COVID-19 in Wuhan, China, and indicated that all those who had saturation ≤90% (n= 14.20%) died, and that those who died were older (median of 70.5 years versus 37 years), with comorbidities such as systemic arterial hypertension (36% versus 7%), cardiovascular disease (36% versus 5%) and diabetes mellitus (43% versus 2%), and had a substantial increase in inflammatory cytokines. Fever was evident at the onset of symptoms (93% versus 85%) and on the 10 ^th day of illness (64% versus 38%). Dyspnea (50% versus 24%) and lymphopenia (79% versus 32%) were also more frequent in this group.

A study that investigated the characteristics and the prognosis factors of COVID-19 infection in a sample comprised of 339 elderly people (≥60 years old) with positive SARS-CoV-2 test results, ³⁰ found that the number of critical and severe cases was greater in the group analyzed compared to cases under 60 years old. The study indicated that 23.6% were classified as being in a critical state , while a further 46.9% were in a severe state. ³⁰

The Chinese Center for Disease Control and Prevention carried out a study with 1,023 positive COVID-19 cases. ²³ Among those who became severely ill, the most common clinical signs were dyspnea, respiratory rate greater than 30 bpm and oxygen saturation under 93%. Among the more critical cases, the signs most found were respiratory insufficiency, septic shock and dysfunction or failure of multiple organs. Lethality was 2.3% in that sample. However, if only the lethality of the critical cases were assessed, the proportion would be much higher, i.e. 49%.

In this review we found that few studies describe the most common signs and symptoms by sex and age, although age is more related to the disease’s severity criteria. It is important to consider that signs and symptoms can vary between the stages of the disease, oscillating between absence of signs and symptoms and septic shock, when the clinical picture becomes worse. It should also be noted that in addition to the diversity of clinical manifestations, some 80% of infected people can remain asymptomatic. It is therefore suggested that suspect cases should be monitored constantly, in view of the manifestations of diverse symptoms, so as not to rule out cases by only considering clinical presentation which, in many cases, is subjective.

Given the imminence of Brazil becoming the world’s new epicenter of the COVID-19 pandemic, it is suggested that health services opt for over-reporting, considering the high sensitivity of the surveillance system, so that whenever signs and symptoms appear that may be related to SARS-CoV-2 infection, isolation measures can be indicated for cases and their contacts, in addition to constant real-time monitoring, based on case investigation and local epidemiological reality. In addition, health services can establish, based on the cases they care for, a set of signs and symptoms that best defines their cases and which guides screening in accordance with the specific situation. Use of telemedicine is a fundamental tool in providing care to suspect and confirmed cases that can stay at home, so as to accompany the progression of their clinical presentation and identify early any worsening of the case, so that appropriate measures can be taken. Whenever possible, it is essential to use molecular or serological diagnostic tests, depending on the day the symptoms started, in addition to laboratory tests and image examinations, to confirm diagnosis of COVID-19.