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Startling findings from an observational study conducted by OUCRU’s Dr Le Van Tan in collaboration with the Hospital for Tropical Diseases, Ho Chi Minh City CDC, the Department of Health and the OUCRU COVID-19 Research Group have shown that it is common for people who are infected with the virus that causes COVID-19 (SARS-CoV-2) to have no symptoms whatsoever.  By testing quarantined people in Vietnam, the team were able to detect the asymptomatic individuals. The virus disappeared faster from the bodies of the asymptomatic carriers than from that of symptomatic individuals, but it appeared that some of them still managed to pass the infection on to others.

Dr Tan and his team conducted a prospective study at a quarantine center for COVID-19 in Ho Chi Minh City, Vietnam. They enrolled quarantined people with confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrolment and daily nose and throat swabs for testing. The team then studied the natural history and transmission potential of asymptomatic and symptomatic individuals.

Between March 10th and April 4th, 2020, 14,000 quarantined people were tested, and 49 were positive. Of these, 30 participated in the study: 13(43%) never had symptoms.  Compared with symptomatic individuals, the people who had no symptoms were less likely to have detectable levels of the virus in their nose and throat swab samples. Only eight out of the 13 asymptomatic individuals had detectable levels of the virus in the samples when they first enrolled in the study, whereas 100% of the patients who were showing symptoms had detectable levels of the virus in their samples.

The research team also tested saliva samples from 27 the enrolled individuals.  RNA – small genetic material from the virus – was detected in 74% of all of the saliva samples; in 64% of the asymptomatic group and 81% of the symptomatic group. The detectability of the virus in saliva samples is good news for future development of rapid tests – since saliva is much easier to collect.  But the high levels of detectable virus in the asymptomatic patients is of concern, since it indicates that even asymptomatic individuals are likely to be able to spread the virus.

The team were able to show that the virus cleared faster from the individuals who had no symptoms – particularly in the first week of followup.  However, even though the virus cleared faster from the asymptomatic patients, and was less frequently detected in the samples taken from the patients, two of  the asymptomatic individuals appeared to transmit the infection to up to four contacts.

The researchers looked at the way the virus was transmitted in a community cluster in Ho Chi Minh City in Vietnam.  With very careful contact tracing and quarantine of contacts, it was possible to analyse how the patients came into contact with the virus.  In the cluster of seven patients who were enrolled in the study, two of the asymptomatic patients appeared to have transmitted the virus to their personal contacts.  The pathway of these transmissions is demonstrated in the figure below.

Dr Le Van Tan said: “Because we don’t know whether the people with whom we are in contact carry the virus or not, it is vital to maintain social distancing and wear a facemask in public. The results strongly support the ongoing rigorous containment approach applied in Vietnam.”

The World Economy Forum cited this publication as a first of the top science stories about COVID-19 in the week of 8-14 June 2020.  Data from Vietnam suggests asymptomatic patients can still transmit the virus to others.

You can download the full manuscript outlining the study and its findings from Clinical Infectious Diseases, here.

OUCRU and the Hospital for Tropical Diseases in Ho Chi Minh City were honored with a visit from British Ambassador Gareth Ward on Friday June 26th.

The Ambassador and his team wanted to visit to pass on their thanks for the excellent care offered to British patients who received treatment at the hospital during the COVID-19 epidemic in Vietnam.

At the height of the epidemic, OUCRU labs were repurposed, to be able to process more than 1,000 tests per day using RT-PCR. This diagnostic work was led by Dr Le Van Tan from our Emerging Infections research group – with hospital and lab staff working around the clock in March to scale up capacity and support the local health system.

OUCRU researchers Prof Jeremy Day and PhD student Nguyen Thanh Ha took part in a Facebook Live conversation with Mr Ian Gibbons, the British Consul General in Ho Chi Minh City on Tuesday 9^th June.

In the entertaining discussion, Jeremy and Ha tackled some of the harmful COVID-19 myths that are circulating, as well as providing interesting information about vaccines and what people can do to protect themselves in the event of second wave.

You can watch a recording of the livestream on the UK in Vietnam Facebook page.

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In an interview with Centre for Tropical Medicine and Global Health, our Dengue Research Group Head Sophie Yacoub talked about Dengue and why dengue research matters not just in Vietnam but globally. Dengue is a viral infection that is spread by mosquitoes, Aedes mosquitoes which are day-biting mosquitoes. Dengue causes a self-limiting viral infection where people have a high fever and feel like body aches and headaches for about seven days. Most people recover but a minority can go on to get a severe disease which can be life-threatening.

Sophie also discusses how OUCRU is working to understand Dengue’s biological mechanisms, targeting it with different therapies, and using innovative technology to monitor patients and predict which will develop severe disease. There have been a number of important discoveries in the past five to ten years.

Under the influence of climate change, it is predicted that more countries will be endemic and the number of 100 million infections a year around the world is increasing. Therefore, she believes it’s really important to invest in this area of research as currently we don’t have any particular therapies as well as vaccines to prevent this disease.

You can find out more about the interview in this link: https://www.tropicalmedicine.ox.ac.uk/wall-of-faces/sophie-yacoub-podcast

Congratulations to Summita Udas and the Public Engagement team at OUCRU-Nepal who have been awarded recognition from the International Society for Neglected Tropical Diseases in the 2020 ISNTD Festival Awards for their photographs and their ‘contribution to community public health and advocacy, and innovative approaches to public engagement and education’.