How pathogenic is it? Will there be a second infection? Zhang Boli explains the hot issues of the XBB strain

Recently, the new variant of Omicron, the XBB strain, has attracted attention from all parties. The Chinese Center for Disease Control and Prevention released information on January 4, saying that the possibility of XBB series variants causing a large-scale epidemic in my country in the short term is low.

So, what are the characteristics of this new strain? How pathogenic is it? Will it cause secondary infection? Does it mainly attack the intestines? How can it be prevented? What should we do if it causes secondary infection? In response to hot issues of social concern, the reporter interviewed Zhang Boli, an academician of the Chinese Academy of Engineering.

What are the characteristics of the new strain?

Zhang Boli introduced that at present, there are reports of XBB.1.5 strains imported from abroad in China, but they have only been detected in a very small number of people in quarantine, and have not yet caused local transmission in the society. According to foreign research data, compared with the BQ.1 strain and the previous BA.5 strain, the XBB.1.5 strain spreads faster . A study in New York showed that it took 26 days for the BQ.1 strain to reach a 30% infection rate, while the XBB.1.5 strain took only 17 days. XBB.1.5 is different from strains of the same family. It has an additional key mutation F486P , which gives it a higher human ACE2 receptor binding affinity and a higher immune escape ability. The new coronavirus is an RNA virus. Because the genetic material of the virus is single-stranded RNA, the structure is unstable and the mutation frequency is high, it may mutate in the future.

How pathogenic is the new strain?

Zhang Boli introduced that according to the existing research data, the pathogenicity of the XBB strain is comparable to other sublineages. The peak of the XBB epidemic in Singapore from October to November last year did not bring a significant peak in the number of deaths. According to information released by the Singapore government on October 14, 2022, there is no evidence that XBB is more pathogenic than previous variants. Even compared with the BA.5 strain, the risk of hospitalization for XBB is reduced by 30%. On October 27, 2022, the World Health Organization issued a statement stating that as of now, there is no data to support that the severity of the disease caused by XBB is significantly different from that of BA.5. There is currently no evidence that the pathogenicity of the XBB strain is greater than that of other strains, nor is there evidence that the XBB strain has special pathogenicity to the gastrointestinal and cardiovascular systems.

Will the new strain cause secondary infection?

Zhang Boli said that the probability of secondary infection with the new coronavirus is mainly related to the human immune level, virus strain mutation, and later personal protection. At present, the XBB strain is different from the BA.5 popular in my country. After a period of time after infection with BA.5, the human immune level decreases. When encountering a new strain with strong immune escape ability, the risk of reinfection will increase to a certain extent. However, there is no need to worry too much. After the new coronavirus infection, the human immune system is already at work. According to current clinical observations, the probability of secondary infection with the new coronavirus within 3 to 6 months after infection is still relatively low. People with normal immune function have a relatively low risk of reinfection in a short period of time, and the symptoms after infection are usually milder than the first time, but there are also individual reports that the symptoms will worsen.

Does the new strain primarily attack the intestines?

Zhang Boli said that some patients infected with the new crown do experience digestive tract symptoms such as vomiting and diarrhea. According to foreign reports, the XBB strain may also cause diarrhea, but from the data collected so far, there are no more common or more serious signs. The XBB strain still mainly invades the respiratory tract, so the statement that "XBB mainly attacks the intestines" is not accurate. There are many reasons for diarrhea after infection with the new crown. It may be due to viral infection of the intestines, causing viral enteritis; it may also be that the toxins produced by the virus induce gastrointestinal dysfunction; or it may be drug-induced diarrhea. Diarrhea caused by new coronavirus infection is usually mild, generally does not require drug treatment, and can be relieved on its own in a short period of time. If the diarrhea is severe, the lost fluids and electrolytes should be replenished. Usually, oral rehydration can achieve the therapeutic effect, rather than blindly taking antidiarrheal drugs and antibacterial drugs.

How to prevent the new strain?

Zhang Boli said that the "main force" against the new coronavirus is one's own immunity, so it is better to stock up on "good health" than on medicine. Adjust your physical condition, pay attention to rest, drink plenty of water, eat more fresh fruits and vegetables, ensure nutrient intake, maintain a good mood, and improve your body's immunity. For those who have recovered from the new coronavirus, the best way to prevent secondary infection during the epidemic is still to implement protective measures, including wearing masks, paying attention to hand hygiene, frequent ventilation, and maintaining social distance . Especially for the elderly and children with "positive to negative" patients , they should keep warm, gather as little as possible, maintain good hygiene habits, pay attention to nutritious diet, enhance immunity, and reduce the risk of reinfection. After being infected with the new coronavirus, some persistent symptoms of the recovered patients still need active intervention. The diagnosis and treatment experience in the past three years has shown that the use of Chinese medicine, acupuncture, massage, and traditional exercises can promote the recovery of patients and improve symptoms such as fatigue and shortness of breath. Taking active intervention measures to promote the recovery of the body and mind of the cured to a better state will also help prevent secondary infection.

What should we do if the new strain causes secondary infection?

Zhang Boli reminded that if reinfection occurs, it is necessary to first distinguish between "re-positive" and secondary infection. "Re-positive" occurs within 2 to 3 weeks after turning negative. Patients generally have no obvious clinical symptoms. It is mainly the residual virus fragments in the body that are detected positive during the discharge process. Generally, it is not contagious; and the secondary infection generally occurs within a few months to a year after the first infection, which is equivalent to a new infection. Generally, clinical symptoms appear, and the viral nucleic acid load is high, which is contagious. "Re-positive" patients do not need further treatment, just pay attention to rest, and eat a reasonable diet and nutrition. Patients with secondary infection need to undergo standardized treatment again, strictly carry out personal protection, do a good job of self-isolation, pay attention to the protection of family members and colleagues, and reduce the risk of epidemic transmission.