Can you get infected with influenza B after influenza A? Actually, there is no need for "after", and the person who infected you is still treating you...

Recently there is a topic called #Can influenza A and influenza B cross-infect each other#. Under this topic, we can see that many medical staff participating in the topic have misunderstood the concept of " cross-infection ".

But then again, influenza A and influenza B can not only cause "cross infection", but also " continuous infection ", " combined infection ", and even serious " secondary infection ".

1. Cross infection

Cross infection is not what many people think, that is, infection with one virus first and then another virus, but any infection that a patient acquires in a medical institution . That is, the patient was not infected or was infected with one pathogen before, but was infected with other pathogens by other infected people in a medical institution.

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Influenza that occurs in hospitals is called hospital-acquired influenza (HAI), which usually occurs during the peak period of community influenza activity each year. In China, HAI accounts for 11.38% of influenza cases. Once HAI occurs, the mortality rate in the ICU may be as high as 30% to 40% . Patients with the following diseases are also at high risk: metabolic diseases (OR = 8.10, 95% CI: 2.46–26.64) malignant tumors (OR = 3.18, 95% CI: 2.12–4.76) any chronic diseases (OR = 2.81, 95% CI: 1.08–9.31) immunosuppression (OR = 2.13, 95% CI: 1.25–3.64) kidney disease (OR = 1.72, 95% CI:1.40–2.10) heart disease (OR = 1.52, 95% CI: 1.03–1.44) diabetes (OR = 1.22, 95% CI: 1.03–1.44) What is more worthy of attention is that medical staff, who are supposed to play the role of "savior" to treat patients, often become the spreaders of viruses in hospitals. A US study showed that the attendance rate of medical staff with flu-like symptoms was as high as 92% . The results of a French susceptible-exposed-infectious model showed that nurses seemed to spread the infection to patients more frequently, with an average daily transmission rate of 1.04 cases, while the transmission rate of doctors was 0.38 cases .

Image source: PPT self-made. For cross-infection of influenza, we not only need to carry out tiered diagnosis and treatment to avoid centralized medical treatment, but also develop online medical treatment and provide good health education. We should also pay more attention to the appalling influenza vaccination rate of medical staff in our country!

2. Continuous Infection

In fact, " consecutive infections " or " multiple infections" are what many people worry about, which are "successive infections" with the same or different types of influenza viruses.

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In an Austrian seasonal study in 2014-2015 ("similar to this year's domestic" first influenza A and then influenza B), researchers analyzed the information of 13 children who had consecutive infections and found that these children were first infected with "influenza A" and then infected with "influenza B". The average time for consecutive infections was " 50 days ". Another retrospective study of four influenza seasons in Austria found that among the 2,318 patients under the age of 18 included in the study, a total of "324 (14%)" had consecutive infections. In addition, in the four influenza seasons, "29" patients (children) were infected with "≥3 times" of influenza, of which 27 (93%) had not received influenza vaccinations, and 2 (3%) had only received influenza vaccinations in one of the influenza seasons.

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3. Co-infection

"Co-infection" is used to describe simultaneous infection with two different pathogens. Although simultaneous infection with different types of influenza viruses is relatively rare, it does exist.

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Data from the five monitoring seasons in Anhui Province from 2009 to 2014 showed that the detection rate of " influenza A " and " influenza B " co-infection in all collected influenza-like illness (ILI) samples was " 0.057% ", and the detection rate of mixed infection in influenza PCR-positive samples was " 0.58% ". Not only can "different types" of "influenza viruses" be infected at the same time, but "other viruses" can also be co-infected with "influenza viruses".

Image source: PPT self-made. A Polish study showed that among the 73 cases of co-infection with influenza virus and other pathogens recorded in the 2015/2016 epidemic season, 17 cases (mostly "children" and "elderly") were infected with both influenza and influenza-like viruses, including: 5 cases of influenza A1 virus and respiratory syncytial virus (RSV); 3 cases of influenza A1 virus, RSV and rhinovirus (type A/B) ; 1 case of influenza A1 virus, influenza B virus and RSV; 2 cases of influenza A1 virus and coronavirus (hCoV OC43) ; 2 cases of influenza A virus (untyped) and RSV; 1 case of influenza A virus (untyped) and coronavirus (hCoV OC43); 1 case of influenza A virus and rhinovirus (type A/B). In fact, it has been found that co-infection with influenza virus and some other pathogens (such as RSV) will "increase the risk of disease severity". Although no RSV vaccine has been approved in mainland China, influenza vaccines are available.

4. Secondary infection

In addition to the above-mentioned infections, there is also a " secondary infection" . The most common complication of influenza is " pneumonia ", among which secondary bacterial pneumonia is usually caused by " Streptococcus pneumoniae " (there is a vaccine), " Haemophilus influenzae " (there is a vaccine) or " Staphylococcus aureus " (there is a vaccine under development).

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The protective effect of pneumococcal vaccine alone against pneumonia in the elderly is about " 26% ", and the protective effect of " simultaneous vaccination " of pneumococcal vaccine and influenza vaccine against pneumonia in the elderly is about " 42% ", which can reduce the number of " doctoral visits " and " hospitalizations " due to pneumonia in the elderly.

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【Summarize】

The best way to prevent influenza is to get a flu vaccine, and the flu vaccine not only prevents influenza A, but also influenza B, so the flu vaccine can prevent both "influenza A" and "influenza B" . Although many people know that the strains are predicted, and have heard many people ask if the prediction is inaccurate, is it useless to get vaccinated? In fact, studies have shown that even if the prevalent strains do not match the vaccine strains, getting a flu vaccine can reduce the severity of influenza disease .

Image source: PPT self-made

In short, vaccination, hand hygiene, more ventilation, less gathering, and wearing masks can reduce the risk of influenza, but they cannot prevent it 100%. Therefore, a scientific combination of multiple methods and timely treatment of illness are the most powerful protection plans.

=丸= Disclaimer: This article was created out of personal interest, only to allow more ordinary people to have a clearer understanding of vaccines. The content and views do not represent any organization, unit, or institution, and have not accepted any form of sponsorship. All pictures are from public online platforms. If the content is incorrect, everyone should do more self-criticism (not).