Since 2012, a population of brown catfish in a lake between Canada and the United States has been observed to have a very high incidence of melanoma, a tumor generally associated with sun exposure. Now, a team from Vermont (USA) has discovered that, in this case, it is a transmissible cancer that spreads from fish to fish like a parasite. This finding represents the fourth known transmissible cancer in the animal kingdom and the first in any species of fish or freshwater animal; previous examples include facial tumor disease in Tasmanian devils, a venereal tumor in dogs, and leukemia-like transmissible diseases in clams, mussels, and other bivalve mollusks. The researchers published their results in Nature and emphasize that the disease poses no known risk to humans.

Data from the Copernicus European Forest Fire Information System (EFFIS) show that, as of 22 July, 119,458 hectares have been burnt in Spain. The average number of hectares burnt from 2006 to 2025 up to this date stands at 35,736 hectares. The fire in the Sierra Norte de Guadalajara, which has scorched more than 30,000 hectares and is still active, together with numerous fire fronts in other provinces and the fire in Los Gallardos (Almería), in which 13 people died, have caused the total area burnt to soar.

Most countries overuse antibiotics, particularly those with the greatest potential to cause resistance, according to a new study published in the journal The Lancet Public Health using data from 186 countries, including Spain. The study estimated optimal national levels of antibiotic use based on the World Health Organisation’s (WHO) AWaRe guidelines, which classify antibiotics into the ‘access’ group – first-line drugs, such as amoxicillin – the ‘caution’ group – more potent drugs with more restricted use – and the ‘reserve’ group – drugs of last resort, for resistant infections. Of the 67 regions with data on antibiotic use, 72 per cent used quantities exceeding those considered optimal, and 99 per cent overused antibiotics in the ‘caution’ group – those that contribute most to the development of resistance. High-income regions used fewer antibiotics than low- and middle-income regions.

On Tuesday, the Council of Ministers approved the draft bill amending the current Tobacco Act, which was passed in 2005. The bill now begins its passage through Parliament and includes new measures to tackle smoking and regulate tobacco-related products. The text prohibits the consumption of tobacco by minors — in addition to its sale —, extends smoke-free zones to outdoor seating areas and other spaces, and restricts the advertising of tobacco-related products. It also treats e-cigarettes and other devices in the same way as traditional tobacco cigarettes, amongst other measures.

Polycystic ovary syndrome (PCOS) has recently been renamed polyendocrine metabolic ovarian syndrome (PMOS), to emphasise its metabolic and endocrine dimensions, rather than viewing it solely as a gynaecological condition. A study involving more than 400,000 women has linked PPOS to an increased incidence of cardiovascular events, specifically atherosclerotic cardiovascular disease. This association was observed independently of traditional cardiovascular risk factors such as diabetes, dyslipidaemia, obesity, and hypertension, suggesting that these factors alone do not fully explain the relationship. The study included women aged 18–50 years with PMOS and drew data from the Optum Clinformatics Data Mart patient database. The findings were published in The Lancet Obstetrics, Gynaecology & Women’s Health.

A Danish study published in JAMA Neurology found an association between long-term exposure to residential road traffic noise and an increased risk of developing Parkinson's disease. The study followed more than three million Danish adults aged 40 years and older for 18 years using data from Denmark's national administrative and health registries. The researchers assessed residential road traffic noise exposure at both the most exposed and the least exposed façades of participants' homes. The study also found that individuals with a quiet façade had a lower risk of developing Parkinson's disease than those whose homes were exposed to high levels of noise on all sides.

The range of CRISPR tools for genome editing can extend beyond nature-inspired designs thanks to proteins designed using artificial intelligence. A new study by Nobel laureate Jennifer Doudna’s team, published in Science, describes the design of synthetic RNA-guided nucleases, with sequences substantially different from those found in nature, which match or exceed the activity of their natural counterparts whilst offering novel properties.

Pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, is an aggressive tumor that is often diagnosed at advanced stages. Some people are at high risk of developing it due to a hereditary predisposition (10% of cases) or an injury. A new Phase 1 clinical trial has tested, in high-risk patients, a vaccine targeting several mutations in the KRAS gene responsible for more than 90% of these tumors. The vaccine has been shown to be safe and has stimulated specific immune responses, detectable in the blood up to two years later, in 90% of the study participants. The study is published in Cancer Discovery.

International entertainment events have a very high carbon footprint. The majority of this stems from emissions caused by spectators’ travel, which account for 82 per cent of the emissions from the 2026 FIFA World Cup and 97 per cent of those from Coldplay’s 2024 European tour, according to a study published in Communications Sustainability which analyses the environmental impact of both mega-events. The researchers propose that organisers should bear part of the carbon costs by rewarding fans with discounts for choosing more environmentally friendly modes of transport to attend the events.

Multiple sclerosis is an autoimmune disease whose cause was a mystery for a long time, but recent studies have strengthened its link to the Epstein-Barr virus, the cause of mononucleosis, or the kissing disease. The challenge now is to define the exact mechanisms involved, which would help in developing therapies. An international team has identified certain components of the virus that tend to trigger a response in patients, which helps explain the effectiveness of some current treatments and could be helpful in developing vaccines and/or antiviral drugs against the disease. The study is published in Science Translational Medicine.