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While coughing, fever and difficulty in breathing are common symptoms of COVID-19, a new case study has found that pink eye is also a reason to be tested for the disease.

The study, published in the Canadian Journal of Ophthalmology, determined that conjunctivitis and keratoconjunctivitis can also be primary symptoms of COVID-19.

The researchers noted that in March, a 29-year-old woman arrived at the Royal Alexandra Hospital's Eye Institute of Alberta with a severe case of conjunctivitis and minimal respiratory symptoms.

After the patient had undergone several days of treatment with little improvement -- and after it had been determined that the woman had recently returned home from Asia -- a resident ordered a COVID-19 test.

The test came back positive, according to the researchers.

"What is interesting in this case, and perhaps very different to how it had been recognised at that specific time, was that the main presentation of the illness was not a respiratory symptom. It was the eye," said Carlos Solarte, an assistant professor at the University of Alberta in Canada.

"There was no fever and no cough, so we weren't led to suspect COVID-19 at the beginning. We didn't know it could present primarily with the eye and not with the lungs," Solarte said.

Academic studies at the outset of the pandemic identified conjunctivitis as a secondary symptoms in about 10 to 15 per cent of COVID-19 cases, he said.

Since then, scientists have gained greater knowledge of how the virus can transmit through and affect the body's mucous membrane system, of which the conjunctiva -- the clear, thin membrane that covers the front surface of the eye -- is an extension.

While the finding provides important new health information for the public, it also makes eye exams more complicated for ophthalmologists and staff, the researchers noted.

"The patient in this case eventually recovered well without any issues. But several of the residents and staff who were in close contact with the patient had to be under quarantine," said Solarte.

"Fortunately, none who were involved in her care also tested positive," he said.

Patients coming into an eye clinic with conjunctivitis and keratoconjunctivitis are now treated as potential cases of COVID-19 and extra precautions are taken by staff, according to the researchers.

Taking multiple courses of antibiotics within a short span of time may do people more harm than good, suggests new research which discovered an association between the number of prescriptions for antibiotics and a higher risk of hospital admissions.

Patients who have had 9 or more antibiotic prescriptions for common infections in the previous three years are 2.26 times more likely to go to hospital with another infection in three or more months, said the researchers.

Patients who had two antibiotic prescriptions were 1.23 times more likely, patients who had three to four prescriptions 1.33 times more likely and patients who had five to eight 1.77 times more likely to go to hospital with another infection.

"We don't know why this is, but overuse of antibiotics might kill the good bacteria in the gut (microbiota) and make us more susceptible to infections, for example," said Professor Tjeerd van Staa from the University of Manchester in Britain.

The study, published in the journal BMC Medicine, is based on the data of two million patients in England and Wales.

The patient records, from 2000 to 2016, covered common infections such as upper respiratory tract, urinary tract, ear and chest infections and excluded long term conditions such as cystic fibrosis and chronic lung disease.

The risks of going to hospital with another infection were related to the number of the antibiotic prescriptions in the previous three years.

A course is defined by the team as being given over a period of one or two weeks.

"GPs (general physicians) care about their patients, and over recent years have worked hard to reduce the prescribing of antibiotics,""Staa said.

"But it is clear GPs do not have the tools to prescribe antibiotics effectively for common infections, especially when patients already have previously used antibiotics.

"They may prescribe numerous courses of antibiotics over several years, which according to our study increases the risk of a more serious infection. That in turn, we show, is linked to hospital admissions," Staa added.

It not clear why hospital admissions are linked to higher prescriptions and research is needed to show what or if any biological factors exist, said the research team.

"Our hope is that, however, a tool we are working for GPs, based on patient history, will be able to calculate the risks associated with taking multiple courses of antibiotics," said Francine Jury from the University of Manchester.

Early treatment with the antiviral drug remdesivir has been found to reduce viral load and prevent lung disease in macaques infected with SARS-CoV-2 that causes COVID-19, according to a study.

The findings, published in the journal Nature on Tuesday, support the early use of remdesivir treatment in patients with COVID-19 to prevent progression to pneumonia.

Researchers from the National Institutes of Health in the US noted that remdesivir has broad antiviral activity and has been shown to be effective against infections with SARS-CoV and MERS-CoV in animal models.

The drug is being tested in human clinical trials for the treatment of COVID-19, they said.

Researcher Emmie de Wit and colleagues investigated the effects of remdesivir treatment in rhesus macaques, a recently established model of SARS-CoV-2 infection.

Two sets of six macaques were inoculated with SARS-CoV-2.

One group was treated with remdesivir 12 hours later -- close to the peak of virus reproduction in the lungs -- and these macaques received treatment every 24 hours until six days after inoculation.

In contrast to the control group, the researchers found that macaques that received remdesivir did not show signs of respiratory disease, and had reduced damage to the lungs.

Viral loads in the lower respiratory tract were also reduced in the treated animals; viral levels were around 100 times lower in the lower-respiratory tract of remdesivir-treated macaques 12 hours after the first dose, they said.

The researchers said that infectious virus could no longer be detected in the treatment group three days after initial infection, but was still detectable in four out of six control animals.

Despite this virus reduction in the lower respiratory tract, no reduction in virus shedding was observed, which indicates that clinical improvement may not equate to a lack of infectiousness, they said.

Dosing of remdesivir in the rhesus macaques is equivalent to that used in humans, the researchers noted.

They cautioned that it is difficult to directly translate the timing of treatment used in corresponding disease stages in humans, because rhesus macaques normally develop only mild disease.

However, researchers said the results indicate that remdesivir treatment of COVID-19 should be initiated as early as possible to achieve the maximum treatment effect.