Malaria remains a devastating disease for tropical and subtropical regions, accounting for an estimated 405,000 deaths and 228 million cases in 2018. In natural settings, the female Anopheles gambiae mosquito — the major malaria vector — feeds on blood multiple times in her lifespan. Such complex behavior is regularly overlooked when mosquitoes are experimentally infected with malaria parasites, limiting our ability to accurately describe potential effects on transmission. In the new study, the researchers examine how additional blood feeding affects the development and transmission potential of Plasmodium falciparum malaria parasites in An. gambiae females.

“We wanted to capture the fact that, in endemic regions, malaria-transmitting mosquitoes are feeding on blood roughly every 2-3 days,” says W. Robert Shaw, a lead author of this study. “Our study shows that this natural behavior strongly promotes the transmission potential of malaria parasites, in previously unappreciated ways.”

The results show that an additional blood feed three days after infection with P. falciparum accelerates the growth of the malaria parasite, thereby shortening the incubation period required before transmission to humans can occur. Incorporating these data into a mathematical model across sub-Saharan Africa reveals that malaria transmission potential is likely higher than previously thought, making disease elimination more difficult. In addition, parasite growth is accelerated in genetically modified mosquitoes with reduced reproductive capacity, suggesting that control strategies using this approach, with the aim of suppressing Anopheles populations, may inadvertently favor malaria transmission. The data also suggest that parasites can be transmitted by younger mosquitoes, which are less susceptible to insecticide killing, with negative implications for the success of insecticide-based strategies. Taken together, the results suggest that younger mosquitoes and those with reduced reproductive ability may provide a larger contribution to infection than previously thought.

According to the authors, the findings have important implications for accurately understanding malaria transmission potential and estimating the true impact of current and future mosquito control measures.

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With the Covid-19 pandemic causing illness and death worldwide, better treatments are urgently needed. One shortcut could be to repurpose existing drugs that were originally developed to treat other conditions. Computational methods can help identify such drugs by simulating how different drugs would interact with SARS-CoV-2, the virus that causes Covid-19.

To aid virtual screening of existing drugs, Zhang and colleagues combined multiple computational techniques that simulate drug-virus interactions from different, complimentary perspectives. They used this hybrid approach to screen 1,906 existing drugs for their potential ability to inhibit replication of SARS-CoV-2 by targeting a viral protein called RNA-dependent RNA polymerase (RdRP).

The novel screening approach identified four promising drugs, which were then tested against SARS-CoV-2 in lab experiments. Two of the drugs, pralatrexate and azithromycin, successfully inhibited replication of the virus. Further lab experiments showed that pralatrexate more strongly inhibited viral replication than did remdesivir, a drug that is currently used to treat some Covid-19 patients.

These findings suggest that pralatrexate could potentially be repurposed to treat Covid-19. However, this chemotherapy drug can prompt significant side effects and is used for people with terminal lymphoma, so immediate use for Covid-19 patients is not guaranteed. Still, the findings support the use of the new screening strategy to identify drugs that could be repurposed.

“We have demonstrated the value of our novel hybrid approach that combines deep-learning technologies with more traditional simulations of molecular dynamics,” Zhang says. He and his colleagues are now developing additional computational methods for generating novel molecular structures that could be developed into new drugs to treat Covid-19.

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Zika virus has triggered large outbreaks in human populations, in some cases causing congenital deformities, fetal loss, or neurological problems in adults. While the yellow fever mosquito Aedes aegypti is considered the primary vector of Zika virus, the Asian tiger mosquito Aedes albopictus has been shown experimentally to transmit the virus and was involved in several transmissions of the virus in France in 2019. Originating from Southeast Asia, Ae. aegypti is an aggressive biter that has invaded the world and is now present on all inhabited continents, including temperate Europe, due to its ability to endure harsh winter conditions. As the second most important vector of human viral pathogens, Ae. albopictus is displacing Ae. aegypti populations due to competitive advantages. But it is not known if Ae. albopictus could trigger large-scale Zika virus epidemics.

To address this question, the researchers exposed Ae. albopictus to Zika virus and assessed infection rates in experiments, modeled the dynamics of Zika virus infection within individual humans, and used epidemiological simulations. The highest risk of transmission occurred during the pre-symptomatic stage of the disease. At this dose, mosquito infection probability was estimated to be 20%, and 21 days were required to reach median systemic infection rates. Despite these unfavorable characteristics for transmission, Ae. albopictus was still able to trigger large outbreaks in a simulated environment in the presence of sufficiently high mosquito densities and biting rates. According to the authors, active surveillance and eradication programs should be implemented in territories occupied by Ae. albopictus to maintain the low risk of Zika virus outbreaks.

The authors conclude, “The complementary combination of dose-dependent experimental infection, modeling of intra-human viremia dynamics, and in silico epidemiological simulations confirms the low epidemic potential of Aedes albopictus for Zika virus.”

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In response to accounts of potential allergic reactions in some people following COVID-19 vaccination in the United Kingdom, that country’s medical regulatory agency advised that individuals with a history of anaphylaxis to a medicine or food should avoid COVID-19 vaccination. After closer review of the data related to allergic reactions, however, the FDA recommended that the vaccines be withheld only from individuals with a history of severe allergic reactions to any component of the COVID-19 vaccine, and the Centers for Disease Control and Prevention advised that all patients be observed for 15 minutes post-vaccination by staff who can identify and manage such reactions. The U.S. agencies do not recommend that people with food or medication allergies avoid vaccination.

To provide insights from allergists’ perspectives, Aleena Banerji, MD, clinical director of the Allergy and Clinical Immunology Unit at MGH and associate professor at Harvard Medical School, and her colleagues have summarized what’s currently known about allergic reactions to vaccines like those developed against COVID-19, and they have proposed detailed advice so that individuals with different allergy histories can safely receive their first COVID-19 vaccine. They also outline steps on safely receiving the second dose in individuals who develop a reaction to their first dose of COVID-19 vaccine.

“As allergists, we want to encourage vaccination by reassuring the public that both FDA-approved COVID-19 vaccines are safe. Our guidelines are built upon the recommendations of U.S. regulatory agencies and provide clear steps to the medical community on how to safely administer both doses of the vaccine in individuals with allergic histories,” says Banerji.

The experts note that allergic reactions to vaccines are rare, with a rate of about 1.3 per 1 million people. They also determined that the Pfizer-BioNTech and Moderna COVID-19 vaccine allergic reactions will have a similarly low rate of occurrence. They stress that vaccine clinics will be monitoring all patients for 15 to 30 minutes and can manage any allergic reactions that occur. Banerji and her co-authors recommend that individuals with a history of anaphylaxis to an injectable drug or vaccine containing polyethylene glycol or polysorbate speak with their allergists before being vaccinated. They stress that patients with severe allergies to foods, oral drugs, latex, or venom can safely receive the COVID-19 vaccines.

Co-senior authors of the review are MGH’s Kimberly G. Blumenthal, MD, MSc, and Brigham and Women’s Elizabeth Phillips, MD. Other co-authors include MGH’s Paige G. Wickner, MD, Rebecca Saff, MD, PhD, Lacey B. Robinson, MD, MPH, Aidan A. Long, MD, Anna R. Wolfson, MD, and David A. Khan, MD; Cosby A. Stone Jr., MD, MPH, of Vanderbilt University Medical Center; and Paul Williams, MD, of the University of Washington School of Medicine.

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After looking at social media posts, parents of young children were better able to recall safety messages such as how to put a baby safely to sleep when the images in the posts aligned with the messages in the text, the researchers found.

The study appears in the Journal of Health Communication.

“Many times, scientists and safety experts aren’t involved in decisions about social media for health agencies and other organizations, and we end up seeing images that have nothing to do with the safety message or, worse, images that contradict the guidance,” said lead author Liz Klein, an associate professor of public health at The Ohio State University.

Take the safe sleep example, for instance. The researchers found posts that advocated a bumper-free crib for baby but used an image of an infant in a crib with bumpers. They saw posts about preventing head injury with bike helmets illustrated by pictures of kids without bike helmets.

“In this study, we were trying to understand how much those mismatches matter — do people understand the message even if the picture isn’t right? Does the picture really matter?” Klein said.

Their answers came from research using eye-tracking technology to gauge the attention young parents paid to various posts, and subsequent tests to see what they recalled about the safety messages.

When the 150 parents in the study were shown a trio of posts with matched imagery and text and three other posts with mismatched visual and written messages, they spent far longer on the matched posts — 5.3 seconds, compared to the 3.3 seconds their eyes lingered on the mismatched posts.

Further, the matched messages appeared to make a difference in understanding and recall of safety messages. After accounting for differences in health literacy and social media use among participants, the researchers found that each second of viewing time on matched posts was associated with a 2.8% increase in a safety knowledge score.

“With nearly 70% of adults reporting use of social media, and many parents using social media and other internet sources to keep current on injury prevention strategies, social media is a great opportunity to broadcast safety and injury prevention messages,” said study co-author Lara McKenzie, a principal investigator in the Center for Injury Research and Policy at Nationwide Children’s Hospital in Columbus.

“As more health organizations and public health agencies use social media to share health information with the public, the findings of our study underscore the need to ensure that the imagery and text in social media posts are aligned.”

Klein said she understands that those managing social media accounts may be drawn to images that are the most attention-grabbing. But when it comes to health and safety, this study suggests that making sure the image and the text are sending the same message is more important.

“If you want people to put their medicine up and out of reach of children, kids to wear their bike helmets or new parents to remember that babies should always go to sleep on their backs, alone and in a crib — that’s where matching matters. Maybe save the eye-grabbing stuff and the humorous posts for different purposes.”

Klein said the findings in this study likely extend beyond child safety messaging to any number of health and safety campaigns, but that there’s more work to be done to understand how best to harness the power of social media for different types of public health communication.

“We need to pay more attention to how we communicate with the people we’re trying to influence with health and safety guidance. All of us can do a better job of thinking about how we use our social media accounts to contribute to better public health,” she said.

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Materials provided by Ohio State University. Original written by Misti Crane. Note: Content may be edited for style and length.