Resistance to HIV drugs is on the rise, and in response, the WHO has issued a new set of guidelines to keep the crisis in check. The immune system can grow resistant to HIV drugs when patients don’t stick to their treatment plan, often because they’re not able to do so. Patients who’ve grown resistant to HIV drugs will start to get sicker and need a different treatment regimen — and if they can’t access one, are at risk of transmitting a resistant virus to others. In some countries, health officials found that more than 10 percent of people starting antiretroviral therapy — a treatment that aims to slow the rate at which the virus makes copies of itself — were infected with a drug-resistant strain of HIV. The new guidelines urge countries to monitor their HIV treatment programs closely for drug resistance.