Sniffing out People with Covid-19

The virus that causes Covid-19 is odorless. If the virus is stored as fine white crystals stuck to the wall in an ampoule in a laboratory, it would look powerless, odorless and without any sign of life.

However, more than 107 million people have been infected with the virus, with the number of the people who have died from the disease exceeding 2.3 million. The rapid transmission, even within families, has made tracing and testing difficult. The vaccination program will not automatically reduce the number of Covid-19 cases in a short time.

Henle-Koch\'s postulate

The method of proving that a germ causes disease is based on the Henle-Koch postulate developed in the early 20th century. First, germs must be found in the sick person and undetected in the non-sick person. Second, the germs obtained from a sick person can be cultured in a suitable media.

Third, cultured germs can cause the same disease in experimental animals. Fourth, germs can be isolated from sick experimental animals after infection.

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Rivers modified HenleKoch\'s postulate for viral disease in 1937. At the time when SARS hit Hong Kong in 2003, researchers from the University of Hong Kong and the University of Erasmus (Netherlands) worked together to apply Rivers\'s criteria.

The virus isolated from SARS patients can cause SARS-like disease when inoculated in a macaque monkey. After the SARS virus had been isolated from infected monkeys, the monkeys showed an immune response to the virus. As a consequence of the Henle-Koch and Rivers postulate, the diagnosis of Covid-19 must be based on the identification of the SARS-CoV-19 virus or a unique part of it.

Therefore, polymerase chain reaction that recognizes RNA or an antigen rapid test that detects viral proteins have become the standard diagnosis of Covid-19 because they can find the unique parts of the RNA or Covid-19 virus protein.

KOMPAS/AGUS SUSANTO

A number of residents line up to undergo a polymerase chain reaction (PCR) test or swab test at the Puskesmas Duren Sawit District, East Jakarta, Tuesday (26/1/2021).

GeNose smells Covid -19

Gadjah Mada University researchers have found a Covid-19 electronic nose called GeNose. The electronic nose consists of sensors for gaseous compounds or organic vapors that generate digital signals, and an artificial intelligence system to identify whether there are digital patterns of unique combinations of vapor compounds associated with certain objects or conditions.

The electronic nose developed since the 1980s consists of a multisensor circuit that can detect the aroma of several chemical compounds.

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The sensor generates complex signals that can be stored in a database and studied by the artificial intelligence system according to the purpose of the system to classify detected odors based on the presence or absence of food contamination, viral infection in a person, drug contamination, toxins in the environment, and others .

The sensors are made of metal oxides, electrically conducting polymers, quartz crystals, sound or optical waves, and electrochemical compounds. The scent signals that are captured and transformed by the sniffing sensors is used as digital feeds for the artificial intelligence system which will then predict the condition that can be validated , namely the presence or absence of virus infection. GeNose has an artificial intelligence system that studies the database that contains variable digital patterns of the breath of people with Covid-19 and people with no Covid-19. So it can recognize the unique markers (signatures) of infection by the virus that causes Covid-19.

GeNose rejection

GeNose cannot smell the virus that causes Covid-19 because the virus is odorless. This fact is inconsistent with the Henle-Koch and Rivers postulate in which the detection of an infectious disease must recognize the germ or specific markers of the germ causing the disease.

This underlies the logic of some experts in rejecting the use of GeNose for Covid-19 detection, either as a screening or diagnostic tool.

KOMPAS/AGUS SUSANTO

Prospective long-distance train passengers follow the GeNose C19 breath sample examination at Pasar Senen Station, Central Jakarta, Wednesday (3/2/2021). The results of the GeNose C19 test will come out in three minutes.

Apart from its incompatibility with the 100-year old postulate, GeNose is rejected because there are errors in classifying Covid-19 carriers and those who are not infected, even though these errors are relatively small. As a screening tool, it has false positive or false negative of between 10 percent and 5 percent. It can even reach below 5 percent in the next development.

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The electronic nose is not new and has been applied in the medical field to detect the scent of sufferers of tuberculosis, cancer, poisoning, and others. Maastricht Hospital, The Netherlands, uses an electronic nose called Aeonose to ensure that patients who will undergo elective (non-emergency) surgery do not have Covid-19, thereby reducing the chance of transmission to other staff or patients at the hospital.

The Henle-Koch postulate?

Without the intention of glorification of the “made-in Indonesia” product, the sensitivity and specificity of Aeonose are 86 percent and 54 percent, respectively, still lower than those of GeNose, which reach 92 percent and 94 percent, respectively.

With the GeNose, the results of the detection can be obtained in only a few minutes. The detection process is also easy as it is carried only by exhaling a plastic bag rather than a swab, and more importantly, the costs are tens of times cheaper, and it can potentially generate higher yields of case findings over the same time frame. Moreover, if it is further improved with a smarter artificial intelligence system, its accuracy as a screening or diagnosis tool will be better.

DOKUMENTASI HARI KUSNANTO

Hari Kusnanto

With its affectivity in the diagnosis of infectious, even non-infectious diseases, it can not only become a faster, easier, but also cheaper disease detection solution. Perhaps it is the time now to adjust the Henle-Koch logics adopted by Rivers to latest technological advances, not only in the biomolecular field, but also in signal-recognition capabilities and artificial intelligence.

Hari Kusnanto, Professor at the Department of Family and Community Medicines, School of Medicine, Gajahmada University (UGM).

This article was translated by Hendarsyah Tarmizi.