First Case of COVID-19 Reinfection Confirmed by Hong Kong Researchers

Hong Kong researchers from Department of Microbiology, Faculty of Medicine, The University of Hong Kong (HKU) has confirmed the world’s first case of COVID-19 reinfection by SARS-CoV-2.

Next-Generation Sequencing (NGS) showed the genome sequence of virus strain is clearly different in 1st and 2nd episode of COVID-19 infection. The patient was recovered from COVID-19 but reinfected afterwards. This is the world fist case of reinfection documented and published in the journal Clinical Infectious Diseases on 24th August 2020.

Until today, 24 million patients infected with 0.8 million deaths in over 200 countries. The pandemic had disrupted the healthcare system and brutally destroyed nations economy.


COVID-19 Reinfection – Patients’ History

The world’s first patient with COVID-19 reinfection is a 33 years old man from Hong Kong. Talking about the first episode, the patient had cough and sputum, sore throat, fever and headache.

These symptoms had been for 3 days. On March 26, 2020, he was diagnosed corona positive after his oropharyngeal saliva taken for SARS-CoV-2 RT-PCR. He was taken to hospital on March 29, 2020.

By the time, all symptoms became less severe. Upon two negative SARS-CoV-2 RT-PCR assays, the patient was discharged on  April 14, 2020. The sample was obtained 24 hours apart from nasopharyngeal and throat.

Second Episode of Infection

The patient was tested positive by SARS-CoV-2 RT-PCR upon entry screening when he returned to Hong Kong from Spain via the United Kingdom. During the second episode of COVID-19, he was asymptomatic.

The patient was then hospitalized. However, no antiviral treatment was prescribed. His body temperature, blood pressure, heart rate, oxygen saturation all were normal. He was asymptomatic all along.

What is SARS-CoV-2 RT-PCR & How it is done?

SARS-CoV-2 RT-PCR is the recommended diagnostic test for coronavirus. A qualitative real-time PCR is used for the detection of the virus. Nucleic acid (RNA) is detected in samples from the upper respiratory tract from suspected individuals.

  1. RNA is extracted from a corona suspected patient’s sample.
  2. Using reverse transcriptase, RNA is converted into DNA.
  3. Primer (short fragments of DNA) complementary to viral DNA is added.
  4. If a virus is present, fragments will be attached to the targeted fragment of viral DNA.
  5. Marker labels are also added to make them detectable.
  6. The mixture is then placed in the RT-PCR machine with a set of instructions to new copies of DNA.
  7. When the new copies are built, marker labels attach to DNA fragments and release the fluorescent dye.
  8. The machine measures the fluorescence and presents it in real-time on a screen.
  9. Virus presence is confirmed when fluorescence surpasses the threshold level.
  10. Scientists measure how many cycles it takes to reach the threshold level that indicates the severity of the infection.


HKU Professor Yuen Kwok-yung talking about First Case of COVID-19 Reinfection


SARS-CoV-2 IgG is the detection of IgG as coronavirus infection elicits development of IgG and IgM antibody. IgM is the first antibody that appears right after the onset of infection. IgG is produced when the body is fighting against infection. IgG is present in the highest amount among all antibodies.

IgG was tested negative against SARS-CoV-2 nucleoprotein for both the first episode and 1 day after hospitalization during the second episode of infection.

Genome Analysis of SARS-CoV-2

Genome Analysis showed that the genome from the first genome is of different lineage from the second genome. The difference between the two genomes that existed in amino acids is located in nucleoprotein, membrane protein, spike protein, accessary and non-structural proteins.

Researchers also blast the sequences of both genomes. The first genome matches closely with the strains collected in March and April 2020 from England and the United States. The second genome indicates its match with strains collected in July and August 2020 from Switzerland and England. The second genome also contains a mutation.

Here is the link to published article:

COVID-19 reinfection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing

Coronavirus Vaccine

SARS-CoV-2 Vaccine

Milken Institute is currently tracking the development of treatments and vaccines for COVID-19. Total of 316 treatments and 206 vaccines are currently in the development process. Since the pandemic has emerged, top developed nations started the start of the art project for coronavirus vaccine development.

Hundreds of vaccines are in the clinical stage and phase 1 of the vaccine development.

MODERNA, US biotech already began phase 3 at end of July 2020. MODERNA is working on RNA-based vaccines. It has been considered to be top biotech to launched coronavirus vaccine in the first quarter of 2021.

PZIFER is also working on RNA-based vaccines. They published their preliminary data in August 2020 and also started phase 3 at the end of July 2020. Now Pfizer vaccine is approved in the UK, Canada and Mexico. FDA approves BioNTech-Pfizer COVID-19 vaccine for emergency use in the US on Friday, 11th November 2020.

Mouthwashes could reduce the transmission of coronavirus. It is also observed in in vitro study mouthwashes significantly reduce the viral load.

Last Words,

Now, when the first case of COVID-19 reinfection is published, so the myth is no more.

Hong Kong researchers explain that the COVID-19 reinfection points out a few implications. Those who are recovered from COVID-19 should be also be vaccinated (when available). Second, they should keep on following sops like wearing a mask and social distancing. 

Quick Facts about COVID-19

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